soroban_sdk/

env.rs

use core::convert::Infallible;

#[cfg(target_family = "wasm")]
pub mod internal {
    use core::convert::Infallible;

    pub use soroban_env_guest::*;
    pub type EnvImpl = Guest;
    pub type MaybeEnvImpl = Guest;

    // In the Guest case, Env::Error is already Infallible so there is no work
    // to do to "reject an error": if an error occurs in the environment, the
    // host will trap our VM and we'll never get here at all.
    pub(crate) fn reject_err<T>(_env: &Guest, r: Result<T, Infallible>) -> Result<T, Infallible> {
        r
    }
}

#[cfg(not(target_family = "wasm"))]
pub mod internal {
    use core::convert::Infallible;

    pub use soroban_env_host::*;
    pub type EnvImpl = Host;
    pub type MaybeEnvImpl = Option<Host>;

    // When we have `feature="testutils"` (or are in cfg(test)) we enable feature
    // `soroban-env-{common,host}/testutils` which in turn adds the helper method
    // `Env::escalate_error_to_panic` to the Env trait.
    //
    // When this is available we want to use it, because it works in concert
    // with a _different_ part of the host that's also `testutils`-gated: the
    // mechanism for emulating the WASM VM error-handling semantics with native
    // contracts. In particular when a WASM contract calls a host function that
    // fails with some error E, the host traps the VM (not returning to it at
    // all) and propagates E to the caller of the contract. This is simulated in
    // the native case by returning a (nontrivial) error E to us here, which we
    // then "reject" back to the host, which stores E in a temporary cell inside
    // any `TestContract` frame in progress and then _panics_, unwinding back to
    // a panic-catcher it installed when invoking the `TestContract` frame, and
    // then extracting E from the frame and returning it to its caller. This
    // simulates the "crash, but catching the error" behavior of the WASM case.
    // This only works if we panic via `escalate_error_to_panic`.
    //
    // (The reason we don't just panic_any() here and let the panic-catcher do a
    // type-based catch is that there might _be_ no panic-catcher around us, and
    // we want to print out a nice error message in that case too, which
    // panic_any() does not do us the favor of producing. This is all very
    // subtle. See also soroban_env_host::Host::escalate_error_to_panic.)
    #[cfg(any(test, feature = "testutils"))]
    pub(crate) fn reject_err<T>(env: &Host, r: Result<T, HostError>) -> Result<T, Infallible> {
        r.map_err(|e| env.escalate_error_to_panic(e))
    }

    // When we're _not_ in a cfg enabling `soroban-env-{common,host}/testutils`,
    // there is no `Env::escalate_error_to_panic` to call, so we just panic
    // here. But this is ok because in that case there is also no multi-contract
    // calling machinery set up, nor probably any panic-catcher installed that
    // we need to hide error values for the benefit of. Any panic in this case
    // is probably going to unwind completely anyways. No special case needed.
    #[cfg(not(any(test, feature = "testutils")))]
    pub(crate) fn reject_err<T>(_env: &Host, r: Result<T, HostError>) -> Result<T, Infallible> {
        r.map_err(|e| panic!("{:?}", e))
    }

    #[doc(hidden)]
    impl<F, T> Convert<F, T> for super::Env
    where
        EnvImpl: Convert<F, T>,
    {
        type Error = <EnvImpl as Convert<F, T>>::Error;
        fn convert(&self, f: F) -> Result<T, Self::Error> {
            self.env_impl.convert(f)
        }
    }
}

pub use internal::xdr;
pub use internal::ContractTtlExtension;
pub use internal::ConversionError;
pub use internal::EnvBase;
pub use internal::Error;
pub use internal::MapObject;
pub use internal::SymbolStr;
pub use internal::TryFromVal;
pub use internal::TryIntoVal;
pub use internal::Val;
pub use internal::VecObject;

pub trait IntoVal<E: internal::Env, T> {
    fn into_val(&self, e: &E) -> T;
}

pub trait FromVal<E: internal::Env, T> {
    fn from_val(e: &E, v: &T) -> Self;
}

impl<E: internal::Env, T, U> FromVal<E, T> for U
where
    U: TryFromVal<E, T>,
{
    fn from_val(e: &E, v: &T) -> Self {
        U::try_from_val(e, v).unwrap_optimized()
    }
}

impl<E: internal::Env, T, U> IntoVal<E, T> for U
where
    T: FromVal<E, Self>,
{
    fn into_val(&self, e: &E) -> T {
        T::from_val(e, self)
    }
}

use crate::auth::InvokerContractAuthEntry;
use crate::unwrap::UnwrapInfallible;
use crate::unwrap::UnwrapOptimized;
use crate::InvokeError;
use crate::{
    crypto::Crypto, deploy::Deployer, events::Events, ledger::Ledger, logs::Logs, prng::Prng,
    storage::Storage, Address, Vec,
};
use internal::{
    AddressObject, Bool, BytesObject, DurationObject, I128Object, I256Object, I256Val, I64Object,
    MuxedAddressObject, StorageType, StringObject, Symbol, SymbolObject, TimepointObject,
    U128Object, U256Object, U256Val, U32Val, U64Object, U64Val, Void,
};

#[doc(hidden)]
#[derive(Clone)]
pub struct MaybeEnv {
    maybe_env_impl: internal::MaybeEnvImpl,
    #[cfg(any(test, feature = "testutils"))]
    test_state: Option<EnvTestState>,
}

#[cfg(target_family = "wasm")]
impl TryFrom<MaybeEnv> for Env {
    type Error = Infallible;

    fn try_from(_value: MaybeEnv) -> Result<Self, Self::Error> {
        Ok(Env {
            env_impl: internal::EnvImpl {},
        })
    }
}

impl Default for MaybeEnv {
    fn default() -> Self {
        Self::none()
    }
}

#[cfg(target_family = "wasm")]
impl MaybeEnv {
    // separate function to be const
    pub const fn none() -> Self {
        Self {
            maybe_env_impl: internal::EnvImpl {},
        }
    }
}

#[cfg(not(target_family = "wasm"))]
impl MaybeEnv {
    // separate function to be const
    pub const fn none() -> Self {
        Self {
            maybe_env_impl: None,
            #[cfg(any(test, feature = "testutils"))]
            test_state: None,
        }
    }
}

#[cfg(target_family = "wasm")]
impl From<Env> for MaybeEnv {
    fn from(value: Env) -> Self {
        MaybeEnv {
            maybe_env_impl: value.env_impl,
        }
    }
}

#[cfg(not(target_family = "wasm"))]
impl TryFrom<MaybeEnv> for Env {
    type Error = ConversionError;

    fn try_from(value: MaybeEnv) -> Result<Self, Self::Error> {
        if let Some(env_impl) = value.maybe_env_impl {
            Ok(Env {
                env_impl,
                #[cfg(any(test, feature = "testutils"))]
                test_state: value.test_state.unwrap_or_default(),
            })
        } else {
            Err(ConversionError)
        }
    }
}

#[cfg(not(target_family = "wasm"))]
impl From<Env> for MaybeEnv {
    fn from(value: Env) -> Self {
        MaybeEnv {
            maybe_env_impl: Some(value.env_impl.clone()),
            #[cfg(any(test, feature = "testutils"))]
            test_state: Some(value.test_state.clone()),
        }
    }
}

/// The [Env] type provides access to the environment the contract is executing
/// within.
///
/// The [Env] provides access to information about the currently executing
/// contract, who invoked it, contract data, functions for signing, hashing,
/// etc.
///
/// Most types require access to an [Env] to be constructed or converted.
#[derive(Clone)]
pub struct Env {
    env_impl: internal::EnvImpl,
    #[cfg(any(test, feature = "testutils"))]
    test_state: EnvTestState,
}

impl Default for Env {
    #[cfg(not(any(test, feature = "testutils")))]
    fn default() -> Self {
        Self {
            env_impl: Default::default(),
        }
    }

    #[cfg(any(test, feature = "testutils"))]
    fn default() -> Self {
        Self::new_with_config(EnvTestConfig::default())
    }
}

#[cfg(any(test, feature = "testutils"))]
#[derive(Default, Clone)]
struct LastEnv {
    test_name: String,
    number: usize,
}

#[cfg(any(test, feature = "testutils"))]
thread_local! {
    static LAST_ENV: RefCell<Option<LastEnv>> = RefCell::new(None);
}

#[cfg(any(test, feature = "testutils"))]
#[derive(Clone, Default)]
struct EnvTestState {
    test_name: Option<String>,
    number: usize,
    config: EnvTestConfig,
    generators: Rc<RefCell<Generators>>,
    auth_snapshot: Rc<RefCell<AuthSnapshot>>,
    snapshot: Option<Rc<LedgerSnapshot>>,
}

/// Config for changing the default behavior of the Env when used in tests.
#[cfg(any(test, feature = "testutils"))]
#[derive(Clone)]
pub struct EnvTestConfig {
    /// Capture a test snapshot when the Env is dropped, causing a test snapshot
    /// JSON file to be written to disk when the Env is no longer referenced.
    /// Defaults to true.
    pub capture_snapshot_at_drop: bool,
    // NOTE: Next time a field needs to be added to EnvTestConfig it will be a breaking change,
    // take the opportunity to make the current field private, new fields private, and settable via
    // functions. Why: So that it is the last time a breaking change is needed to the type.
}

#[cfg(any(test, feature = "testutils"))]
impl Default for EnvTestConfig {
    fn default() -> Self {
        Self {
            capture_snapshot_at_drop: true,
        }
    }
}

impl Env {
    /// Panic with the given error.
    ///
    /// Equivalent to `panic!`, but with an error value instead of a string.
    #[doc(hidden)]
    #[cfg(feature = "experimental_spec_shaking_v2")]
    #[inline(always)]
    pub fn panic_with_error<I>(&self, error: I) -> !
    where
        I: Into<internal::Error> + crate::SpecShakingMarker,
    {
        I::spec_shaking_marker();
        self.panic_with_error_inner(error.into())
    }

    /// Panic with the given error.
    ///
    /// Equivalent to `panic!`, but with an error value instead of a string.
    #[doc(hidden)]
    #[cfg(not(feature = "experimental_spec_shaking_v2"))]
    #[inline(always)]
    pub fn panic_with_error(&self, error: impl Into<internal::Error>) -> ! {
        self.panic_with_error_inner(error.into())
    }

    #[inline(always)]
    fn panic_with_error_inner(&self, error: internal::Error) -> ! {
        _ = internal::Env::fail_with_error(self, error);
        #[cfg(target_family = "wasm")]
        core::arch::wasm32::unreachable();
        #[cfg(not(target_family = "wasm"))]
        unreachable!();
    }

    /// Get a [Storage] for accessing and updating persistent data owned by the
    /// currently executing contract.
    #[inline(always)]
    pub fn storage(&self) -> Storage {
        Storage::new(self)
    }

    /// Get [Events] for publishing events associated with the
    /// currently executing contract.
    #[inline(always)]
    pub fn events(&self) -> Events {
        Events::new(self)
    }

    /// Get a [Ledger] for accessing the current ledger.
    #[inline(always)]
    pub fn ledger(&self) -> Ledger {
        Ledger::new(self)
    }

    /// Get a deployer for deploying contracts.
    #[inline(always)]
    pub fn deployer(&self) -> Deployer {
        Deployer::new(self)
    }

    /// Get a [Crypto] for accessing the current cryptographic functions.
    #[inline(always)]
    pub fn crypto(&self) -> Crypto {
        Crypto::new(self)
    }

    /// # ⚠️ Hazardous Materials
    ///
    /// Get a [CryptoHazmat][crate::crypto::CryptoHazmat] for accessing the
    /// cryptographic functions that are not generally recommended. Using them
    /// incorrectly can introduce security vulnerabilities. Use [Crypto] if
    /// possible.
    #[cfg_attr(any(test, feature = "hazmat-crypto"), visibility::make(pub))]
    #[cfg_attr(feature = "docs", doc(cfg(feature = "hazmat-crypto")))]
    #[inline(always)]
    pub(crate) fn crypto_hazmat(&self) -> crate::crypto::CryptoHazmat {
        crate::crypto::CryptoHazmat::new(self)
    }

    /// Get a [Prng] for accessing the current functions which provide pseudo-randomness.
    ///
    /// # Warning
    ///
    /// **The pseudo-random generator returned is not suitable for
    /// security-sensitive work.**
    #[inline(always)]
    pub fn prng(&self) -> Prng {
        Prng::new(self)
    }

    /// Get the Address object corresponding to the current executing contract.
    pub fn current_contract_address(&self) -> Address {
        let address = internal::Env::get_current_contract_address(self).unwrap_infallible();
        unsafe { Address::unchecked_new(self.clone(), address) }
    }

    #[doc(hidden)]
    pub(crate) fn require_auth_for_args(&self, address: &Address, args: Vec<Val>) {
        internal::Env::require_auth_for_args(self, address.to_object(), args.to_object())
            .unwrap_infallible();
    }

    #[doc(hidden)]
    pub(crate) fn require_auth(&self, address: &Address) {
        internal::Env::require_auth(self, address.to_object()).unwrap_infallible();
    }

    /// Invokes a function of a contract that is registered in the [Env].
    ///
    /// # Panics
    ///
    /// Will panic if the `contract_id` does not match a registered contract,
    /// `func` does not match a function of the referenced contract, or the
    /// number of `args` do not match the argument count of the referenced
    /// contract function.
    ///
    /// Will panic if the contract that is invoked fails or aborts in anyway.
    ///
    /// Will panic if the value returned from the contract cannot be converted
    /// into the type `T`.
    pub fn invoke_contract<T>(
        &self,
        contract_address: &Address,
        func: &crate::Symbol,
        args: Vec<Val>,
    ) -> T
    where
        T: TryFromVal<Env, Val>,
    {
        let rv = internal::Env::call(
            self,
            contract_address.to_object(),
            func.to_symbol_val(),
            args.to_object(),
        )
        .unwrap_infallible();
        T::try_from_val(self, &rv)
            .map_err(|_| ConversionError)
            .unwrap()
    }

    /// Invokes a function of a contract that is registered in the [Env],
    /// returns an error if the invocation fails for any reason.
    pub fn try_invoke_contract<T, E>(
        &self,
        contract_address: &Address,
        func: &crate::Symbol,
        args: Vec<Val>,
    ) -> Result<Result<T, T::Error>, Result<E, InvokeError>>
    where
        T: TryFromVal<Env, Val>,
        E: TryFrom<Error>,
        E::Error: Into<InvokeError>,
    {
        let rv = internal::Env::try_call(
            self,
            contract_address.to_object(),
            func.to_symbol_val(),
            args.to_object(),
        )
        .unwrap_infallible();
        match internal::Error::try_from_val(self, &rv) {
            Ok(err) => Err(E::try_from(err).map_err(Into::into)),
            Err(ConversionError) => Ok(T::try_from_val(self, &rv)),
        }
    }

    /// Authorizes sub-contract calls on behalf of the current contract.
    ///
    /// All the direct calls that the current contract performs are always
    /// considered to have been authorized. This is only needed to authorize
    /// deeper calls that originate from the next contract call from the current
    /// contract.
    ///
    /// For example, if the contract A calls contract B, contract
    /// B calls contract C and contract C calls `A.require_auth()`, then an
    /// entry corresponding to C call has to be passed in `auth_entries`. It
    /// doesn't matter if contract B called `require_auth` or not. If contract A
    /// calls contract B again, then `authorize_as_current_contract` has to be
    /// called again with the respective entries.
    ///
    /// When testing a contract call that uses `authorize_as_current_contract`, avoid
    /// using [`mock_all_auths_allowing_non_root_auth`][Self::mock_all_auths_allowing_non_root_auth].
    /// A test that uses this mock will not fail if a missing or incorrect
    /// `authorize_as_current_contract` call is present. It is recommended to use other
    /// authorization mocking functions like [`mock_auths`][Self::mock_auths]
    /// or [`set_auths`][Self::set_auths] if needed.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{
    ///     auth::{ContractContext, InvokerContractAuthEntry, SubContractInvocation},
    ///     contract, contractimpl, vec, Address, Env, IntoVal, Symbol,
    /// };
    ///
    /// // Contract C performs authorization for addr
    /// #[contract]
    /// pub struct ContractC;
    ///
    /// #[contractimpl]
    /// impl ContractC {
    ///     pub fn do_auth(_env: Env, addr: Address, amount: i128) -> i128 {
    ///         addr.require_auth();
    ///         amount
    ///     }
    /// }
    ///
    /// // Contract B performs authorization for `addr` and invokes Contract C with
    /// // `addr` and `amount` as arguments.
    /// #[contract]
    /// pub struct ContractB;
    ///
    /// #[contractimpl]
    /// impl ContractB {
    ///     pub fn call_c(env: Env, addr: Address, contract_c: Address, amount: i128) -> i128 {
    ///         addr.require_auth();
    ///         ContractCClient::new(&env, &contract_c).do_auth(&addr, &amount)
    ///     }
    /// }
    ///
    /// // Contract A authorizes Contract B to call Contract C on its behalf with `addr` and
    /// // `amount` as arguments.
    /// #[contract]
    /// pub struct ContractA;
    ///
    /// #[contractimpl]
    /// impl ContractA {
    ///     pub fn call_b(env: Env, contract_b: Address, contract_c: Address, amount: i128) -> i128 {
    ///         let curr_contract = env.current_contract_address();
    ///         // Authorize the sub-call Contract B makes to Contract C
    ///         env.authorize_as_current_contract(vec![
    ///             &env,
    ///             InvokerContractAuthEntry::Contract(SubContractInvocation {
    ///                 context: ContractContext {
    ///                     contract: contract_c.clone(),
    ///                     fn_name: Symbol::new(&env, "do_auth"),
    ///                     args: vec![&env, curr_contract.into_val(&env), amount.into_val(&env)],
    ///                 },
    ///                 sub_invocations: vec![&env],
    ///             }),
    ///         ]);
    ///         ContractBClient::new(&env, &contract_b).call_c(&curr_contract, &contract_c, &amount)
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_a = env.register(ContractA, ());
    ///     let contract_b = env.register(ContractB, ());
    ///     let contract_c = env.register(ContractC, ());
    ///
    ///     // Auths are not mocked to ensure `authorize_as_current_contract`
    ///     // is working as intended. If Contract A includes additional auths, consider
    ///     // using `mock_auths` or `set_auths` for those authorizations.
    ///
    ///     let client = ContractAClient::new(&env, &contract_a);
    ///     let result = client.call_b(&contract_b, &contract_c, &100);
    ///     assert_eq!(result, 100);
    /// }
    /// ```
    pub fn authorize_as_current_contract(&self, auth_entries: Vec<InvokerContractAuthEntry>) {
        internal::Env::authorize_as_curr_contract(self, auth_entries.to_object())
            .unwrap_infallible();
    }

    /// Get the [Logs] for logging debug events.
    #[inline(always)]
    #[deprecated(note = "use [Env::logs]")]
    #[doc(hidden)]
    pub fn logger(&self) -> Logs {
        self.logs()
    }

    /// Get the [Logs] for logging debug events.
    #[inline(always)]
    pub fn logs(&self) -> Logs {
        Logs::new(self)
    }
}

#[doc(hidden)]
#[cfg(not(target_family = "wasm"))]
impl Env {
    pub(crate) fn is_same_env(&self, other: &Self) -> bool {
        self.env_impl.is_same(&other.env_impl)
    }
}

#[cfg(any(test, feature = "testutils"))]
use crate::testutils::cost_estimate::CostEstimate;
#[cfg(any(test, feature = "testutils"))]
use crate::{
    auth,
    testutils::{
        budget::Budget, cost_estimate::NetworkInvocationResourceLimits, default_ledger_info,
        Address as _, AuthSnapshot, AuthorizedInvocation, ContractFunctionSet, EventsSnapshot,
        Generators, Ledger as _, MockAuth, MockAuthContract, Register, Snapshot,
        SnapshotSourceInput, StellarAssetContract, StellarAssetIssuer,
    },
    Bytes, BytesN, ConstructorArgs,
};
#[cfg(any(test, feature = "testutils"))]
use core::{cell::RefCell, cell::RefMut};
#[cfg(any(test, feature = "testutils"))]
use internal::{InvocationEvent, InvocationResourceLimits};
#[cfg(any(test, feature = "testutils"))]
use soroban_ledger_snapshot::LedgerSnapshot;
#[cfg(any(test, feature = "testutils"))]
use std::{path::Path, rc::Rc};
#[cfg(any(test, feature = "testutils"))]
use xdr::{LedgerEntry, LedgerKey, LedgerKeyContractData, SorobanAuthorizationEntry};

#[cfg(any(test, feature = "testutils"))]
#[cfg_attr(feature = "docs", doc(cfg(feature = "testutils")))]
impl Env {
    #[doc(hidden)]
    pub fn in_contract(&self) -> bool {
        self.env_impl.has_frame().unwrap()
    }

    #[doc(hidden)]
    pub fn host(&self) -> &internal::Host {
        &self.env_impl
    }

    #[doc(hidden)]
    pub(crate) fn with_generator<T>(&self, f: impl FnOnce(RefMut<'_, Generators>) -> T) -> T {
        f((*self.test_state.generators).borrow_mut())
    }

    /// Create an Env with the test config.
    pub fn new_with_config(config: EnvTestConfig) -> Env {
        struct EmptySnapshotSource();

        impl internal::storage::SnapshotSource for EmptySnapshotSource {
            fn get(
                &self,
                _key: &Rc<xdr::LedgerKey>,
            ) -> Result<Option<(Rc<xdr::LedgerEntry>, Option<u32>)>, soroban_env_host::HostError>
            {
                Ok(None)
            }
        }

        let rf = Rc::new(EmptySnapshotSource());

        Env::new_for_testutils(config, rf, None, None, None)
    }

    /// Change the test config of an Env.
    pub fn set_config(&mut self, config: EnvTestConfig) {
        self.test_state.config = config;
    }

    /// Used by multiple constructors to configure test environments consistently.
    fn new_for_testutils(
        config: EnvTestConfig,
        recording_footprint: Rc<dyn internal::storage::SnapshotSource>,
        generators: Option<Rc<RefCell<Generators>>>,
        ledger_info: Option<internal::LedgerInfo>,
        snapshot: Option<Rc<LedgerSnapshot>>,
    ) -> Env {
        // Store in the Env the name of the test it is for, and a number so that within a test
        // where one or more Env's have been created they can be uniquely identified relative to
        // each other.

        let test_name = match std::thread::current().name() {
            // When doc tests are running they're all run with the thread name main. There's no way
            // to detect which doc test is being run.
            Some(name) if name != "main" => Some(name.to_owned()),
            _ => None,
        };
        let number = if let Some(ref test_name) = test_name {
            LAST_ENV.with_borrow_mut(|l| {
                if let Some(last_env) = l.as_mut() {
                    if test_name != &last_env.test_name {
                        last_env.test_name = test_name.clone();
                        last_env.number = 1;
                        1
                    } else {
                        let next_number = last_env.number + 1;
                        last_env.number = next_number;
                        next_number
                    }
                } else {
                    *l = Some(LastEnv {
                        test_name: test_name.clone(),
                        number: 1,
                    });
                    1
                }
            })
        } else {
            1
        };

        let storage = internal::storage::Storage::with_recording_footprint(recording_footprint);
        let budget = internal::budget::Budget::default();
        let env_impl = internal::EnvImpl::with_storage_and_budget(storage, budget.clone());
        env_impl
            .set_source_account(xdr::AccountId(xdr::PublicKey::PublicKeyTypeEd25519(
                xdr::Uint256([0; 32]),
            )))
            .unwrap();
        env_impl
            .set_diagnostic_level(internal::DiagnosticLevel::Debug)
            .unwrap();
        env_impl.set_base_prng_seed([0; 32]).unwrap();

        let auth_snapshot = Rc::new(RefCell::new(AuthSnapshot::default()));
        let auth_snapshot_in_hook = auth_snapshot.clone();
        env_impl
            .set_invocation_hook(Some(Rc::new(move |host, event| {
                match event {
                    InvocationEvent::Start => {}
                    InvocationEvent::Finish => {
                        let new_auths = host
                            .get_authenticated_authorizations()
                            // If an error occurs getting the authenticated authorizations
                            // it means that no auth has occurred.
                            .unwrap();
                        (*auth_snapshot_in_hook).borrow_mut().0.push(new_auths);
                    }
                }
            })))
            .unwrap();
        env_impl.enable_invocation_metering();
        env_impl
            .set_invocation_resource_limits(Some(InvocationResourceLimits::mainnet()))
            .unwrap();

        let env = Env {
            env_impl,
            test_state: EnvTestState {
                test_name,
                number,
                config,
                generators: generators.unwrap_or_default(),
                snapshot,
                auth_snapshot,
            },
        };

        let ledger_info = ledger_info.unwrap_or_else(default_ledger_info);
        env.ledger().set(ledger_info);

        env
    }

    /// Returns the resources metered during the last top level contract
    /// invocation.    
    ///
    /// In order to get non-`None` results, `enable_invocation_metering` has to
    /// be called and at least one invocation has to happen after that.
    ///
    /// Take the return value with a grain of salt. The returned resources mostly
    /// correspond only to the operations that have happened during the host
    /// invocation, i.e. this won't try to simulate the work that happens in
    /// production scenarios (e.g. certain XDR roundtrips). This also doesn't try
    /// to model resources related to the transaction size.
    ///
    /// The returned value is as useful as the preceding setup, e.g. if a test
    /// contract is used instead of a Wasm contract, all the costs related to
    /// VM instantiation and execution, as well as Wasm reads/rent bumps will be
    /// missed.
    ///
    /// While the resource metering may be useful for contract optimization,
    /// keep in mind that resource and fee estimation may be imprecise. Use
    /// simulation with RPC in order to get the exact resources for submitting
    /// the transactions to the network.    
    pub fn cost_estimate(&self) -> CostEstimate {
        CostEstimate::new(self.clone())
    }

    /// Register a contract with the [Env] for testing.
    ///
    /// Pass the contract type when the contract is defined in the current crate
    /// and is being registered natively. Pass the contract wasm bytes when the
    /// contract has been loaded as wasm.
    ///
    /// Pass the arguments for the contract's constructor, or `()` if none. For
    /// contracts with a constructor, use the contract's generated `Args` type
    /// to construct the arguments with the appropriate types for invoking
    /// the constructor during registration.
    ///
    /// Returns the address of the registered contract that is the same as the
    /// contract id passed in.
    ///
    /// If you need to specify the address the contract should be registered at,
    /// use [`Env::register_at`].
    ///
    /// ### Examples
    /// Register a contract defined in the current crate, by specifying the type
    /// name:
    /// ```
    /// use soroban_sdk::{contract, contractimpl, testutils::Address as _, Address, BytesN, Env, Symbol};
    ///
    /// #[contract]
    /// pub struct Contract;
    ///
    /// #[contractimpl]
    /// impl Contract {
    ///     pub fn __constructor(_env: Env, _input: u32) {
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(Contract, ContractArgs::__constructor(&123,));
    /// }
    /// ```
    /// Register a contract wasm, by specifying the wasm bytes:
    /// ```
    /// use soroban_sdk::{testutils::Address as _, Address, BytesN, Env};
    ///
    /// const WASM: &[u8] = include_bytes!("../doctest_fixtures/contract.wasm");
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(WASM, ());
    /// }
    /// ```
    pub fn register<'a, C, A>(&self, contract: C, constructor_args: A) -> Address
    where
        C: Register,
        A: ConstructorArgs,
    {
        contract.register(self, None, constructor_args)
    }

    /// Register a contract with the [Env] for testing.
    ///
    /// Passing a contract ID for the first arguments registers the contract
    /// with that contract ID.
    ///
    /// Registering a contract that is already registered replaces it.
    /// Use re-registration with caution as it does not exist in the real
    /// (on-chain) environment. Specifically, the new contract's constructor
    /// will be called again during re-registration. That behavior only exists
    /// for this test utility and is not reproducible on-chain, where contract
    /// Wasm updates don't cause constructor to be called.
    ///
    /// Pass the contract type when the contract is defined in the current crate
    /// and is being registered natively. Pass the contract wasm bytes when the
    /// contract has been loaded as wasm.
    ///
    /// Returns the address of the registered contract that is the same as the
    /// contract id passed in.
    ///
    /// ### Examples
    /// Register a contract defined in the current crate, by specifying the type
    /// name:
    /// ```
    /// use soroban_sdk::{contract, contractimpl, testutils::Address as _, Address, BytesN, Env, Symbol};
    ///
    /// #[contract]
    /// pub struct Contract;
    ///
    /// #[contractimpl]
    /// impl Contract {
    ///     pub fn __constructor(_env: Env, _input: u32) {
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = Address::generate(&env);
    ///     env.register_at(&contract_id, Contract, (123_u32,));
    /// }
    /// ```
    /// Register a contract wasm, by specifying the wasm bytes:
    /// ```
    /// use soroban_sdk::{testutils::Address as _, Address, BytesN, Env};
    ///
    /// const WASM: &[u8] = include_bytes!("../doctest_fixtures/contract.wasm");
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = Address::generate(&env);
    ///     env.register_at(&contract_id, WASM, ());
    /// }
    /// ```
    pub fn register_at<C, A>(
        &self,
        contract_id: &Address,
        contract: C,
        constructor_args: A,
    ) -> Address
    where
        C: Register,
        A: ConstructorArgs,
    {
        contract.register(self, contract_id, constructor_args)
    }

    /// Register a contract with the [Env] for testing.
    ///
    /// Passing a contract ID for the first arguments registers the contract
    /// with that contract ID. Providing `None` causes the Env to generate a new
    /// contract ID that is assigned to the contract.
    ///
    /// If a contract has a constructor defined, then it will be called with
    /// no arguments. If a constructor takes arguments, use `register`.
    ///
    /// Registering a contract that is already registered replaces it.
    /// Use re-registration with caution as it does not exist in the real
    /// (on-chain) environment. Specifically, the new contract's constructor
    /// will be called again during re-registration. That behavior only exists
    /// for this test utility and is not reproducible on-chain, where contract
    /// Wasm updates don't cause constructor to be called.
    ///
    /// Returns the address of the registered contract.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, BytesN, Env, Symbol};
    ///
    /// #[contract]
    /// pub struct HelloContract;
    ///
    /// #[contractimpl]
    /// impl HelloContract {
    ///     pub fn hello(env: Env, recipient: Symbol) -> Symbol {
    ///         todo!()
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register_contract(None, HelloContract);
    /// }
    /// ```
    #[deprecated(note = "use `register`")]
    pub fn register_contract<'a, T: ContractFunctionSet + 'static>(
        &self,
        contract_id: impl Into<Option<&'a Address>>,
        contract: T,
    ) -> Address {
        self.register_contract_with_constructor(contract_id, contract, ())
    }

    /// Register a contract with the [Env] for testing.
    ///
    /// This acts the in the same fashion as `register_contract`, but allows
    /// passing arguments to the contract's constructor.
    ///
    /// Passing a contract ID for the first arguments registers the contract
    /// with that contract ID. Providing `None` causes the Env to generate a new
    /// contract ID that is assigned to the contract.
    ///
    /// Registering a contract that is already registered replaces it.
    /// Use re-registration with caution as it does not exist in the real
    /// (on-chain) environment. Specifically, the new contract's constructor
    /// will be called again during re-registration. That behavior only exists
    /// for this test utility and is not reproducible on-chain, where contract
    /// Wasm updates don't cause constructor to be called.
    ///
    /// Returns the address of the registered contract.
    pub(crate) fn register_contract_with_constructor<
        'a,
        T: ContractFunctionSet + 'static,
        A: ConstructorArgs,
    >(
        &self,
        contract_id: impl Into<Option<&'a Address>>,
        contract: T,
        constructor_args: A,
    ) -> Address {
        struct InternalContractFunctionSet<T: ContractFunctionSet>(pub(crate) T);
        impl<T: ContractFunctionSet> internal::ContractFunctionSet for InternalContractFunctionSet<T> {
            fn call(
                &self,
                func: &Symbol,
                env_impl: &internal::EnvImpl,
                args: &[Val],
            ) -> Option<Val> {
                let env = Env {
                    env_impl: env_impl.clone(),
                    test_state: Default::default(),
                };
                self.0.call(
                    crate::Symbol::try_from_val(&env, func)
                        .unwrap_infallible()
                        .to_string()
                        .as_str(),
                    env,
                    args,
                )
            }
        }

        let contract_id = if let Some(contract_id) = contract_id.into() {
            contract_id.clone()
        } else {
            Address::generate(self)
        };
        self.env_impl
            .register_test_contract_with_constructor(
                contract_id.to_object(),
                Rc::new(InternalContractFunctionSet(contract)),
                constructor_args.into_val(self).to_object(),
            )
            .unwrap();
        contract_id
    }

    /// Register a contract in a Wasm file with the [Env] for testing.
    ///
    /// Passing a contract ID for the first arguments registers the contract
    /// with that contract ID. Providing `None` causes the Env to generate a new
    /// contract ID that is assigned to the contract.
    ///
    /// Registering a contract that is already registered replaces it.
    /// Use re-registration with caution as it does not exist in the real
    /// (on-chain) environment. Specifically, the new contract's constructor
    /// will be called again during re-registration. That behavior only exists
    /// for this test utility and is not reproducible on-chain, where contract
    /// Wasm updates don't cause constructor to be called.
    ///
    /// Returns the address of the registered contract.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{BytesN, Env};
    ///
    /// const WASM: &[u8] = include_bytes!("../doctest_fixtures/contract.wasm");
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     env.register_contract_wasm(None, WASM);
    /// }
    /// ```
    #[deprecated(note = "use `register`")]
    pub fn register_contract_wasm<'a>(
        &self,
        contract_id: impl Into<Option<&'a Address>>,
        contract_wasm: impl IntoVal<Env, Bytes>,
    ) -> Address {
        let wasm_hash: BytesN<32> = self.deployer().upload_contract_wasm(contract_wasm);
        self.register_contract_with_optional_contract_id_and_executable(
            contract_id,
            xdr::ContractExecutable::Wasm(xdr::Hash(wasm_hash.into())),
            crate::vec![&self],
        )
    }

    /// Register a contract in a Wasm file with the [Env] for testing.
    ///
    /// This acts the in the same fashion as `register_contract`, but allows
    /// passing arguments to the contract's constructor.
    ///
    /// Passing a contract ID for the first arguments registers the contract
    /// with that contract ID. Providing `None` causes the Env to generate a new
    /// contract ID that is assigned to the contract.
    ///
    /// Registering a contract that is already registered replaces it.
    /// Use re-registration with caution as it does not exist in the real
    /// (on-chain) environment. Specifically, the new contract's constructor
    /// will be called again during re-registration. That behavior only exists
    /// for this test utility and is not reproducible on-chain, where contract
    /// Wasm updates don't cause constructor to be called.
    ///
    /// Returns the address of the registered contract.
    pub(crate) fn register_contract_wasm_with_constructor<'a>(
        &self,
        contract_id: impl Into<Option<&'a Address>>,
        contract_wasm: impl IntoVal<Env, Bytes>,
        constructor_args: impl ConstructorArgs,
    ) -> Address {
        let wasm_hash: BytesN<32> = self.deployer().upload_contract_wasm(contract_wasm);
        self.register_contract_with_optional_contract_id_and_executable(
            contract_id,
            xdr::ContractExecutable::Wasm(xdr::Hash(wasm_hash.into())),
            constructor_args.into_val(self),
        )
    }

    /// Register the built-in Stellar Asset Contract with provided admin address.
    ///
    /// Returns a utility struct that contains the contract ID of the registered
    /// token contract, as well as methods to read and update issuer flags.
    ///
    /// The contract will wrap a randomly-generated Stellar asset. This function
    /// is useful for using in the tests when an arbitrary token contract
    /// instance is needed.
    pub fn register_stellar_asset_contract_v2(&self, admin: Address) -> StellarAssetContract {
        let issuer_pk = self.with_generator(|mut g| g.address());
        let issuer_id = xdr::AccountId(xdr::PublicKey::PublicKeyTypeEd25519(xdr::Uint256(
            issuer_pk.clone(),
        )));

        let k = Rc::new(xdr::LedgerKey::Account(xdr::LedgerKeyAccount {
            account_id: issuer_id.clone(),
        }));

        if self.host().get_ledger_entry(&k).unwrap().is_none() {
            let v = Rc::new(xdr::LedgerEntry {
                data: xdr::LedgerEntryData::Account(xdr::AccountEntry {
                    account_id: issuer_id.clone(),
                    balance: 0,
                    flags: 0,
                    home_domain: Default::default(),
                    inflation_dest: None,
                    num_sub_entries: 0,
                    seq_num: xdr::SequenceNumber(0),
                    thresholds: xdr::Thresholds([1; 4]),
                    signers: xdr::VecM::default(),
                    ext: xdr::AccountEntryExt::V0,
                }),
                last_modified_ledger_seq: 0,
                ext: xdr::LedgerEntryExt::V0,
            });
            self.host().add_ledger_entry(&k, &v, None).unwrap();
        }

        let asset = xdr::Asset::CreditAlphanum4(xdr::AlphaNum4 {
            asset_code: xdr::AssetCode4([b'a', b'a', b'a', 0]),
            issuer: issuer_id.clone(),
        });
        let create = xdr::HostFunction::CreateContract(xdr::CreateContractArgs {
            contract_id_preimage: xdr::ContractIdPreimage::Asset(asset.clone()),
            executable: xdr::ContractExecutable::StellarAsset,
        });

        let token_id: Address = self
            .env_impl
            .invoke_function(create)
            .unwrap()
            .try_into_val(self)
            .unwrap();

        let prev_auth_manager = self.env_impl.snapshot_auth_manager().unwrap();
        self.env_impl
            .switch_to_recording_auth_inherited_from_snapshot(&prev_auth_manager)
            .unwrap();
        let admin_result = self.try_invoke_contract::<(), Error>(
            &token_id,
            &soroban_sdk_macros::internal_symbol_short!("set_admin"),
            (admin,).try_into_val(self).unwrap(),
        );
        self.env_impl.set_auth_manager(prev_auth_manager).unwrap();
        admin_result.unwrap().unwrap();

        let issuer = StellarAssetIssuer::new(self.clone(), issuer_id);
        StellarAssetContract::new(token_id, issuer, asset)
    }

    /// Register the built-in Stellar Asset Contract with provided admin address.
    ///
    /// Returns the contract ID of the registered token contract.
    ///
    /// The contract will wrap a randomly-generated Stellar asset. This function
    /// is useful for using in the tests when an arbitrary token contract
    /// instance is needed.
    #[deprecated(note = "use [Env::register_stellar_asset_contract_v2]")]
    pub fn register_stellar_asset_contract(&self, admin: Address) -> Address {
        self.register_stellar_asset_contract_v2(admin).address()
    }

    fn register_contract_with_optional_contract_id_and_executable<'a>(
        &self,
        contract_id: impl Into<Option<&'a Address>>,
        executable: xdr::ContractExecutable,
        constructor_args: Vec<Val>,
    ) -> Address {
        if let Some(contract_id) = contract_id.into() {
            self.register_contract_with_contract_id_and_executable(
                contract_id,
                executable,
                constructor_args,
            );
            contract_id.clone()
        } else {
            self.register_contract_with_source(executable, constructor_args)
        }
    }

    fn register_contract_with_source(
        &self,
        executable: xdr::ContractExecutable,
        constructor_args: Vec<Val>,
    ) -> Address {
        let args_vec: std::vec::Vec<xdr::ScVal> =
            constructor_args.iter().map(|v| v.into_val(self)).collect();
        let constructor_args = args_vec.try_into().unwrap();
        let prev_auth_manager = self.env_impl.snapshot_auth_manager().unwrap();
        self.env_impl
            .switch_to_recording_auth_inherited_from_snapshot(&prev_auth_manager)
            .unwrap();
        let create_result = self
            .env_impl
            .invoke_function(xdr::HostFunction::CreateContractV2(
                xdr::CreateContractArgsV2 {
                    contract_id_preimage: xdr::ContractIdPreimage::Address(
                        xdr::ContractIdPreimageFromAddress {
                            address: xdr::ScAddress::Contract(xdr::ContractId(xdr::Hash(
                                self.with_generator(|mut g| g.address()),
                            ))),
                            salt: xdr::Uint256([0; 32]),
                        },
                    ),
                    executable,
                    constructor_args,
                },
            ));

        self.env_impl.set_auth_manager(prev_auth_manager).unwrap();

        create_result.unwrap().try_into_val(self).unwrap()
    }

    /// Set authorizations and signatures in the environment which will be
    /// consumed by contracts when they invoke [`Address::require_auth`] or
    /// [`Address::require_auth_for_args`] functions.
    ///
    /// Requires valid signatures for the authorization to be successful.
    ///
    /// This function can also be called on contract clients.
    ///
    /// To mock auth for testing, without requiring valid signatures, use
    /// [`mock_all_auths`][Self::mock_all_auths] or
    /// [`mock_auths`][Self::mock_auths]. If mocking of auths is enabled,
    /// calling [`set_auths`][Self::set_auths] disables any mocking.
    pub fn set_auths(&self, auths: &[SorobanAuthorizationEntry]) {
        self.env_impl
            .set_authorization_entries(auths.to_vec())
            .unwrap();
    }

    /// Mock authorizations in the environment which will cause matching invokes
    /// of [`Address::require_auth`] and [`Address::require_auth_for_args`] to
    /// pass.
    ///
    /// This function can also be called on contract clients.
    ///
    /// Authorizations not matching a mocked auth will fail.
    ///
    /// To mock all auths, use [`mock_all_auths`][Self::mock_all_auths].
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, Env, Address, testutils::{Address as _, MockAuth, MockAuthInvoke}, IntoVal};
    ///
    /// #[contract]
    /// pub struct HelloContract;
    ///
    /// #[contractimpl]
    /// impl HelloContract {
    ///     pub fn hello(env: Env, from: Address) {
    ///         from.require_auth();
    ///         // TODO
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(HelloContract, ());
    ///
    ///     let client = HelloContractClient::new(&env, &contract_id);
    ///     let addr = Address::generate(&env);
    ///     client.mock_auths(&[
    ///         MockAuth {
    ///             address: &addr,
    ///             invoke: &MockAuthInvoke {
    ///                 contract: &contract_id,
    ///                 fn_name: "hello",
    ///                 args: (&addr,).into_val(&env),
    ///                 sub_invokes: &[],
    ///             },
    ///         },
    ///     ]).hello(&addr);
    /// }
    /// ```
    pub fn mock_auths(&self, auths: &[MockAuth]) {
        for a in auths {
            self.register_at(a.address, MockAuthContract, ());
        }
        let auths = auths
            .iter()
            .cloned()
            .map(Into::into)
            .collect::<std::vec::Vec<_>>();
        self.env_impl.set_authorization_entries(auths).unwrap();
    }

    /// Mock all calls to the [`Address::require_auth`] and
    /// [`Address::require_auth_for_args`] functions in invoked contracts,
    /// having them succeed as if authorization was provided.
    ///
    /// When mocking is enabled, if the [`Address`] being authorized is the
    /// address of a contract, that contract's `__check_auth` function will not
    /// be called, and the contract does not need to exist or be registered in
    /// the test.
    ///
    /// When mocking is enabled, if the [`Address`] being authorized is the
    /// address of an account, the account does not need to exist.
    ///
    /// This function can also be called on contract clients.
    ///
    /// To disable mocking, see [`set_auths`][Self::set_auths].
    ///
    /// To access a list of auths that have occurred, see [`auths`][Self::auths].
    ///
    /// It is not currently possible to mock a subset of auths.
    ///
    /// A test that uses `mock_all_auths` without verifying the resulting
    /// authorization tree via [`auths`][Self::auths] can pass even when a contract
    /// is missing a `require_auth` check. Use [`auths`][Self::auths] after
    /// the contract call to assert that the expected authorizations were required.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, Env, Address, IntoVal, symbol_short};
    /// use soroban_sdk::testutils::{Address as _, AuthorizedFunction, AuthorizedInvocation};
    ///
    /// #[contract]
    /// pub struct HelloContract;
    ///
    /// #[contractimpl]
    /// impl HelloContract {
    ///     pub fn hello(env: Env, from: Address) {
    ///         from.require_auth();
    ///         // TODO
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(HelloContract, ());
    ///
    ///     env.mock_all_auths();
    ///
    ///     let client = HelloContractClient::new(&env, &contract_id);
    ///     let addr = Address::generate(&env);
    ///     client.hello(&addr);
    ///
    ///     // Verify that the expected authorization was required.
    ///     assert_eq!(
    ///         env.auths(),
    ///         [(
    ///             addr.clone(),
    ///             AuthorizedInvocation {
    ///                 function: AuthorizedFunction::Contract((
    ///                     contract_id,
    ///                     symbol_short!("hello"),
    ///                     (&addr,).into_val(&env),
    ///                 )),
    ///                 sub_invocations: [].into(),
    ///             }
    ///         )]
    ///     );
    /// }
    /// ```
    pub fn mock_all_auths(&self) {
        self.env_impl.switch_to_recording_auth(true).unwrap();
    }

    /// A version of [`mock_all_auths`][Self::mock_all_auths] that allows authorizations that are not
    /// present in the root invocation.
    ///
    /// Refer to [`mock_all_auths`][Self::mock_all_auths] documentation for general information and
    /// prefer using [`mock_all_auths`][Self::mock_all_auths] unless non-root authorization is required.
    ///
    /// The only difference from [`mock_all_auths`][Self::mock_all_auths] is that this won't return an
    /// error when `require_auth` hasn't been called in the root invocation for
    /// any given address. This is useful to test contracts that bundle calls to
    /// another contract without atomicity requirements (i.e. any contract call
    /// can be frontrun).
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, Env, Address, testutils::Address as _};
    ///
    /// #[contract]
    /// pub struct ContractA;
    ///
    /// #[contractimpl]
    /// impl ContractA {
    ///     pub fn do_auth(env: Env, addr: Address) {
    ///         addr.require_auth();
    ///     }
    /// }
    /// #[contract]
    /// pub struct ContractB;
    ///
    /// #[contractimpl]
    /// impl ContractB {
    ///     pub fn call_a(env: Env, contract_a: Address, addr: Address) {
    ///         // Notice there is no `require_auth` call here.
    ///         ContractAClient::new(&env, &contract_a).do_auth(&addr);
    ///     }
    /// }
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_a = env.register(ContractA, ());
    ///     let contract_b = env.register(ContractB, ());
    ///     // The regular `env.mock_all_auths()` would result in the call
    ///     // failure.
    ///     env.mock_all_auths_allowing_non_root_auth();
    ///
    ///     let client = ContractBClient::new(&env, &contract_b);
    ///     let addr = Address::generate(&env);
    ///     client.call_a(&contract_a, &addr);
    /// }
    /// ```
    pub fn mock_all_auths_allowing_non_root_auth(&self) {
        self.env_impl.switch_to_recording_auth(false).unwrap();
    }

    /// Returns a list of authorization trees that were seen during the last
    /// contract or authorized host function invocation.
    ///
    /// Use this in tests to verify that the expected authorizations with the
    /// expected arguments are required.
    ///
    /// The return value is a vector of authorizations represented by tuples of
    /// `(address, AuthorizedInvocation)`. `AuthorizedInvocation` describes the
    /// tree of `require_auth_for_args(address, args)` from the contract
    /// functions (or `require_auth` with all the arguments of the function
    /// invocation). It also might contain the authorized host functions (
    /// currently CreateContract is the only such function) in case if
    /// corresponding host functions have been called.
    ///
    /// Refer to documentation for `AuthorizedInvocation` for detailed
    /// information on its contents.
    ///
    /// The order of the returned vector is defined by the order of
    /// [`Address::require_auth`] calls. Repeated calls to
    /// [`Address::require_auth`] with the same address and args in the same
    /// tree of contract invocations will appear only once in the vector.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, testutils::{Address as _, AuthorizedFunction, AuthorizedInvocation}, symbol_short, Address, Symbol, Env, IntoVal};
    ///
    /// #[contract]
    /// pub struct Contract;
    ///
    /// #[contractimpl]
    /// impl Contract {
    ///     pub fn transfer(env: Env, address: Address, amount: i128) {
    ///         address.require_auth();
    ///     }
    ///     pub fn transfer2(env: Env, address: Address, amount: i128) {
    ///         address.require_auth_for_args((amount / 2,).into_val(&env));
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # #[cfg(feature = "testutils")]
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(Contract, ());
    ///     let client = ContractClient::new(&env, &contract_id);
    ///     env.mock_all_auths();
    ///     let address = Address::generate(&env);
    ///     client.transfer(&address, &1000_i128);
    ///     assert_eq!(
    ///         env.auths(),
    ///         [(
    ///             address.clone(),
    ///             AuthorizedInvocation {
    ///                 function: AuthorizedFunction::Contract((
    ///                     client.address.clone(),
    ///                     symbol_short!("transfer"),
    ///                     (&address, 1000_i128,).into_val(&env)
    ///                 )),
    ///                 sub_invocations: [].into()
    ///             }
    ///         )]
    ///     );
    ///
    ///     client.transfer2(&address, &1000_i128);
    ///     assert_eq!(
    ///         env.auths(),
    ///         [(
    ///             address.clone(),
    ///             AuthorizedInvocation {
    ///                 function: AuthorizedFunction::Contract((
    ///                     client.address.clone(),
    ///                     symbol_short!("transfer2"),
    ///                     // `transfer2` requires auth for (amount / 2) == (1000 / 2) == 500.
    ///                     (500_i128,).into_val(&env)
    ///                 )),
    ///                 sub_invocations: [].into()
    ///             }
    ///         )]
    ///     );
    /// }
    /// # #[cfg(not(feature = "testutils"))]
    /// # fn main() { }
    /// ```
    pub fn auths(&self) -> std::vec::Vec<(Address, AuthorizedInvocation)> {
        (*self.test_state.auth_snapshot)
            .borrow()
            .0
            .last()
            .cloned()
            .unwrap_or_default()
            .into_iter()
            .map(|(sc_addr, invocation)| {
                (
                    xdr::ScVal::Address(sc_addr).try_into_val(self).unwrap(),
                    AuthorizedInvocation::from_xdr(self, &invocation),
                )
            })
            .collect()
    }

    /// Invokes the special `__check_auth` function of contracts that implement
    /// the custom account interface.
    ///
    /// `__check_auth` can't be called outside of the host-managed `require_auth`
    /// calls. This test utility allows testing custom account contracts without
    /// the need to setup complex contract call trees and enabling the enforcing
    /// auth on the host side.
    ///
    /// This function requires to provide the template argument for error. Use
    /// `soroban_sdk::Error` if `__check_auth` doesn't return a special
    /// contract error and use the error with `contracterror` attribute
    /// otherwise.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contracterror, contractimpl, testutils::{Address as _, BytesN as _}, vec, auth::Context, BytesN, Env, Vec, Val};
    ///
    /// #[contracterror]
    /// #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
    /// #[repr(u32)]
    /// pub enum NoopAccountError {
    ///     SomeError = 1,
    /// }
    /// #[contract]
    /// struct NoopAccountContract;
    /// #[contractimpl]
    /// impl NoopAccountContract {
    ///
    ///     #[allow(non_snake_case)]
    ///     pub fn __check_auth(
    ///         _env: Env,
    ///         _signature_payload: BytesN<32>,
    ///         signature: Val,
    ///         _auth_context: Vec<Context>,
    ///     ) -> Result<(), NoopAccountError> {
    ///         if signature.is_void() {
    ///             Err(NoopAccountError::SomeError)
    ///         } else {
    ///             Ok(())
    ///         }
    ///     }
    /// }
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let e: Env = Default::default();
    ///     let account_contract = NoopAccountContractClient::new(&e, &e.register(NoopAccountContract, ()));
    ///     // Non-successful call of `__check_auth` with a `contracterror` error.
    ///     assert_eq!(
    ///         e.try_invoke_contract_check_auth::<NoopAccountError>(
    ///             &account_contract.address,
    ///             &BytesN::from_array(&e, &[0; 32]),
    ///             ().into(),
    ///             &vec![&e],
    ///         ),
    ///         // The inner `Result` is for conversion error and will be Ok
    ///         // as long as a valid error type used.
    ///         Err(Ok(NoopAccountError::SomeError))
    ///     );
    ///     // Successful call of `__check_auth` with a `soroban_sdk::InvokeError`
    ///     // error - this should be compatible with any error type.
    ///     assert_eq!(
    ///         e.try_invoke_contract_check_auth::<soroban_sdk::InvokeError>(
    ///             &account_contract.address,
    ///             &BytesN::from_array(&e, &[0; 32]),
    ///             0_i32.into(),
    ///             &vec![&e],
    ///         ),
    ///         Ok(())
    ///     );
    /// }
    /// ```
    pub fn try_invoke_contract_check_auth<E>(
        &self,
        contract: &Address,
        signature_payload: &BytesN<32>,
        signature: Val,
        auth_context: &Vec<auth::Context>,
    ) -> Result<(), Result<E, InvokeError>>
    where
        E: TryFrom<Error>,
        E::Error: Into<InvokeError>,
    {
        let args = Vec::from_array(
            self,
            [signature_payload.to_val(), signature, auth_context.to_val()],
        );
        let res = self
            .host()
            .call_account_contract_check_auth(contract.to_object(), args.to_object());
        match res {
            Ok(rv) => Ok(rv.into_val(self)),
            Err(e) => Err(e.error.try_into().map_err(Into::into)),
        }
    }

    fn register_contract_with_contract_id_and_executable(
        &self,
        contract_address: &Address,
        executable: xdr::ContractExecutable,
        constructor_args: Vec<Val>,
    ) {
        let contract_id = contract_address.contract_id();
        let data_key = xdr::ScVal::LedgerKeyContractInstance;
        let key = Rc::new(LedgerKey::ContractData(LedgerKeyContractData {
            contract: xdr::ScAddress::Contract(contract_id.clone()),
            key: data_key.clone(),
            durability: xdr::ContractDataDurability::Persistent,
        }));

        let instance = xdr::ScContractInstance {
            executable,
            storage: Default::default(),
        };

        let entry = Rc::new(LedgerEntry {
            ext: xdr::LedgerEntryExt::V0,
            last_modified_ledger_seq: 0,
            data: xdr::LedgerEntryData::ContractData(xdr::ContractDataEntry {
                contract: xdr::ScAddress::Contract(contract_id.clone()),
                key: data_key,
                val: xdr::ScVal::ContractInstance(instance),
                durability: xdr::ContractDataDurability::Persistent,
                ext: xdr::ExtensionPoint::V0,
            }),
        });
        let live_until_ledger = self.ledger().sequence() + 1;
        self.host()
            .add_ledger_entry(&key, &entry, Some(live_until_ledger))
            .unwrap();
        self.env_impl
            .call_constructor_for_stored_contract_unsafe(&contract_id, constructor_args.to_object())
            .unwrap();
    }

    /// Run the function as if executed by the given contract ID.
    ///
    /// Used to write or read contract data, or take other actions in tests for
    /// setting up tests or asserting on internal state.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, Env, Symbol};
    ///
    /// #[contract]
    /// pub struct HelloContract;
    ///
    /// #[contractimpl]
    /// impl HelloContract {
    ///     pub fn set_storage(env: Env, key: Symbol, val: Symbol) {
    ///         env.storage().persistent().set(&key, &val);
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(HelloContract, ());
    ///     let client = HelloContractClient::new(&env, &contract_id);
    ///
    ///     let key = Symbol::new(&env, "foo");
    ///     let val = Symbol::new(&env, "bar");
    ///
    ///     // Set storage using the contract
    ///     client.set_storage(&key, &val);
    ///
    ///     // Successfully read the storage key
    ///     let result = env.as_contract(&contract_id, || {
    ///         env.storage()
    ///             .persistent()
    ///             .get::<Symbol, Symbol>(&key)
    ///             .unwrap()
    ///     });
    ///     assert_eq!(result, val);
    /// }
    /// ```
    pub fn as_contract<T>(&self, id: &Address, f: impl FnOnce() -> T) -> T {
        let id = id.contract_id();
        let func = Symbol::from_small_str("");
        let mut t: Option<T> = None;
        self.env_impl
            .with_test_contract_frame(id, func, || {
                t = Some(f());
                Ok(().into())
            })
            .unwrap();
        t.unwrap()
    }

    /// Run the function as if executed by the given contract ID. Returns an
    /// error if the function execution fails for any reason.
    ///
    /// Used to write or read contract data, or take other actions in tests for
    /// setting up tests or asserting on internal state.
    ///
    /// ### Examples
    /// ```
    /// use soroban_sdk::{contract, contractimpl, xdr::{ScErrorCode, ScErrorType}, Env, Error, Symbol};
    ///
    /// #[contract]
    /// pub struct HelloContract;
    ///
    /// #[contractimpl]
    /// impl HelloContract {
    ///     pub fn set_storage(env: Env, key: Symbol, val: Symbol) {
    ///         env.storage().persistent().set(&key, &val);
    ///     }
    /// }
    ///
    /// #[test]
    /// fn test() {
    /// # }
    /// # fn main() {
    ///     let env = Env::default();
    ///     let contract_id = env.register(HelloContract, ());
    ///     let client = HelloContractClient::new(&env, &contract_id);
    ///
    ///     let key = Symbol::new(&env, "foo");
    ///     let val = Symbol::new(&env, "bar");
    ///
    ///     // Set storage using the contract
    ///     client.set_storage(&key, &val);
    ///
    ///     // Successfully read the storage key
    ///     let result = env.try_as_contract::<Symbol, Error>(&contract_id, || {
    ///         env.storage()
    ///             .persistent()
    ///             .get::<Symbol, Symbol>(&key)
    ///             .unwrap()
    ///     });
    ///     assert_eq!(result, Ok(val));
    ///
    ///     // Attempting to extend TTL of a non-existent key throws an error
    ///     let new_key = Symbol::new(&env, "baz");
    ///     let result = env.try_as_contract(&contract_id, || {
    ///         env.storage().persistent().extend_ttl(&new_key, 1, 100);
    ///     });
    ///     assert_eq!(
    ///         result,
    ///         Err(Ok(Error::from_type_and_code(
    ///             ScErrorType::Storage,
    ///             ScErrorCode::MissingValue
    ///         )))
    ///     );
    /// }
    /// ```
    pub fn try_as_contract<T, E>(
        &self,
        id: &Address,
        f: impl FnOnce() -> T,
    ) -> Result<T, Result<E, InvokeError>>
    where
        E: TryFrom<Error>,
        E::Error: Into<InvokeError>,
    {
        let id = id.contract_id();
        let func = Symbol::from_small_str("");
        let mut t: Option<T> = None;
        let result = self.env_impl.try_with_test_contract_frame(id, func, || {
            t = Some(f());
            Ok(().into())
        });

        match result {
            Ok(_) => Ok(t.unwrap()),
            Err(e) => Err(E::try_from(e.error).map_err(Into::into)),
        }
    }

    /// Creates a new Env loaded with the [`Snapshot`].
    ///
    /// The ledger info and state in the snapshot are loaded into the Env.
    ///
    /// Events, as an output source only, are not loaded into the Env.
    pub fn from_snapshot(s: Snapshot) -> Env {
        Env::new_for_testutils(
            EnvTestConfig::default(),
            Rc::new(s.ledger.clone()),
            Some(Rc::new(RefCell::new(s.generators))),
            Some(s.ledger.ledger_info()),
            Some(Rc::new(s.ledger.clone())),
        )
    }

    /// Creates a new Env loaded with the ledger snapshot loaded from the file.
    ///
    /// The ledger info and state in the snapshot are loaded into the Env.
    ///
    /// Events, as an output source only, are not loaded into the Env.
    ///
    /// ### Panics
    ///
    /// If there is any error reading the file.
    pub fn from_snapshot_file(p: impl AsRef<Path>) -> Env {
        Self::from_snapshot(Snapshot::read_file(p).unwrap())
    }

    /// Create a snapshot from the Env's current state.
    pub fn to_snapshot(&self) -> Snapshot {
        Snapshot {
            generators: (*self.test_state.generators).borrow().clone(),
            auth: (*self.test_state.auth_snapshot).borrow().clone(),
            ledger: self.to_ledger_snapshot(),
            events: self.to_events_snapshot(),
        }
    }

    /// Create a snapshot file from the Env's current state.
    ///
    /// ### Panics
    ///
    /// If there is any error writing the file.
    pub fn to_snapshot_file(&self, p: impl AsRef<Path>) {
        self.to_snapshot().write_file(p).unwrap();
    }

    /// Creates a new Env loaded with the snapshot source.
    ///
    /// The ledger info and state from the snapshot source are loaded into the Env.
    pub fn from_ledger_snapshot(input: impl Into<SnapshotSourceInput>) -> Env {
        let SnapshotSourceInput {
            source,
            ledger_info,
            snapshot,
        } = input.into();

        Env::new_for_testutils(
            EnvTestConfig::default(), // TODO: Allow setting the config.
            source,
            None,
            ledger_info,
            snapshot,
        )
    }

    /// Creates a new Env loaded with the ledger snapshot loaded from the file.
    ///
    /// ### Panics
    ///
    /// If there is any error reading the file.
    pub fn from_ledger_snapshot_file(p: impl AsRef<Path>) -> Env {
        Self::from_ledger_snapshot(LedgerSnapshot::read_file(p).unwrap())
    }

    /// Create a snapshot from the Env's current state.
    pub fn to_ledger_snapshot(&self) -> LedgerSnapshot {
        let snapshot = self.test_state.snapshot.clone().unwrap_or_default();
        let mut snapshot = (*snapshot).clone();
        snapshot.set_ledger_info(self.ledger().get());
        snapshot.update_entries(&self.host().get_stored_entries().unwrap());
        snapshot
    }

    /// Create a snapshot file from the Env's current state.
    ///
    /// ### Panics
    ///
    /// If there is any error writing the file.
    pub fn to_ledger_snapshot_file(&self, p: impl AsRef<Path>) {
        self.to_ledger_snapshot().write_file(p).unwrap();
    }

    /// Create an events snapshot from the Env's current state.
    pub(crate) fn to_events_snapshot(&self) -> EventsSnapshot {
        EventsSnapshot(
            self.host()
                .get_events()
                .unwrap()
                .0
                .into_iter()
                .filter(|e| match e.event.type_ {
                    // Keep only system and contract events, because event
                    // snapshots are used in test snapshots, and intended to be
                    // stable over time because the goal is to record meaningful
                    // observable behaviors. Diagnostic events are observable,
                    // but events have no stability guarantees and are intended
                    // to be used by developers when debugging, tracing, and
                    // observing, not by systems that integrate.
                    xdr::ContractEventType::System | xdr::ContractEventType::Contract => true,
                    xdr::ContractEventType::Diagnostic => false,
                })
                .map(Into::into)
                .collect(),
        )
    }

    /// Get the budget that tracks the resources consumed for the environment.
    #[deprecated(note = "use cost_estimate().budget()")]
    pub fn budget(&self) -> Budget {
        Budget::new(self.env_impl.budget_cloned())
    }
}

#[cfg(any(test, feature = "testutils"))]
impl Drop for Env {
    fn drop(&mut self) {
        // If the env impl (Host) is finishable, that means this Env is the last
        // Env to hold a reference to the Host. The Env should only write a test
        // snapshot at that point when no other references to the host exist,
        // because it is only when there are no other references that the host
        // is being dropped.
        if self.env_impl.can_finish() && self.test_state.config.capture_snapshot_at_drop {
            self.to_test_snapshot_file();
        }
    }
}

#[doc(hidden)]
#[cfg(any(test, feature = "testutils"))]
impl Env {
    /// Create a snapshot file for the currently executing test.
    ///
    /// Writes the file to the `test_snapshots/{test-name}.N.json` path where
    /// `N` is incremented for each unique `Env` in the test.
    ///
    /// Use to record the observable behavior of a test, and changes to that
    /// behavior over time. Commit the test snapshot file to version control and
    /// watch for changes in it on contract change, SDK upgrade, protocol
    /// upgrade, and other important events.
    ///
    /// No file will be created if the environment has no meaningful data such
    /// as stored entries or events.
    ///
    /// ### Panics
    ///
    /// If there is any error writing the file.
    pub(crate) fn to_test_snapshot_file(&self) {
        let snapshot = self.to_snapshot();

        // Don't write a snapshot that has no data in it.
        if snapshot.ledger.entries().into_iter().count() == 0
            && snapshot.events.0.is_empty()
            && snapshot.auth.0.is_empty()
        {
            return;
        }

        // Determine path to write test snapshots to.
        let Some(test_name) = &self.test_state.test_name else {
            // If there's no test name, we're not in a test context, so don't write snapshots.
            return;
        };
        let number = self.test_state.number;
        // Break up the test name into directories, using :: as the separator.
        // The :: module separator cannot be written into the filename because
        // some operating systems (e.g. Windows) do not allow the : character in
        // filenames.
        let test_name_path = test_name
            .split("::")
            .map(|p| std::path::Path::new(p).to_path_buf())
            .reduce(|p0, p1| p0.join(p1))
            .expect("test name to not be empty");
        let dir = std::path::Path::new("test_snapshots");
        let p = dir
            .join(&test_name_path)
            .with_extension(format!("{number}.json"));

        // Write test snapshots to file.
        eprintln!("Writing test snapshot file for test {test_name:?} to {p:?}.");
        snapshot.write_file(p).unwrap();
    }
}

#[doc(hidden)]
impl internal::EnvBase for Env {
    type Error = Infallible;

    // This exists to allow code in conversion paths to upgrade an Error to an
    // Env::Error with some control granted to the underlying Env (and panic
    // paths kept out of the host). We delegate this to our env_impl and then,
    // since our own Error type is Infallible, immediately throw it into either
    // the env_impl's Error escalation path (if testing), or just plain panic.
    #[cfg(not(target_family = "wasm"))]
    fn error_from_error_val(&self, e: crate::Error) -> Self::Error {
        let host_err = self.env_impl.error_from_error_val(e);
        #[cfg(any(test, feature = "testutils"))]
        self.env_impl.escalate_error_to_panic(host_err);
        #[cfg(not(any(test, feature = "testutils")))]
        panic!("{:?}", host_err);
    }

    // When targeting wasm we don't even need to do that, just delegate to
    // the Guest's impl, which calls core::arch::wasm32::unreachable.
    #[cfg(target_family = "wasm")]
    #[allow(unreachable_code)]
    fn error_from_error_val(&self, e: crate::Error) -> Self::Error {
        self.env_impl.error_from_error_val(e)
    }

    fn check_protocol_version_lower_bound(&self, v: u32) -> Result<(), Self::Error> {
        Ok(self
            .env_impl
            .check_protocol_version_lower_bound(v)
            .unwrap_optimized())
    }

    fn check_protocol_version_upper_bound(&self, v: u32) -> Result<(), Self::Error> {
        Ok(self
            .env_impl
            .check_protocol_version_upper_bound(v)
            .unwrap_optimized())
    }

    // Note: the function `escalate_error_to_panic` only exists _on the `Env`
    // trait_ when the feature `soroban-env-common/testutils` is enabled. This
    // is because the host wants to never have this function even _compiled in_
    // when building for production, as it might be accidentally called (we have
    // mistakenly done so with conversion and comparison traits in the past).
    //
    // As a result, we only implement it here (fairly meaninglessly) when we're
    // in `cfg(test)` (which enables `soroban-env-host/testutils` thus
    // `soroban-env-common/testutils`) or when we've had our own `testutils`
    // feature enabled (which does the same).
    //
    // See the `internal::reject_err` functions above for more detail about what
    // it actually does (when implemented for real, on the host). In this
    // not-very-serious impl, since `Self::Error` is `Infallible`, this instance
    // can never actually be called and so its body is just a trivial
    // transformation from one empty type to another, for Type System Reasons.
    #[cfg(any(test, feature = "testutils"))]
    fn escalate_error_to_panic(&self, e: Self::Error) -> ! {
        match e {}
    }

    fn bytes_copy_from_slice(
        &self,
        b: BytesObject,
        b_pos: U32Val,
        slice: &[u8],
    ) -> Result<BytesObject, Self::Error> {
        Ok(self
            .env_impl
            .bytes_copy_from_slice(b, b_pos, slice)
            .unwrap_optimized())
    }

    fn bytes_copy_to_slice(
        &self,
        b: BytesObject,
        b_pos: U32Val,
        slice: &mut [u8],
    ) -> Result<(), Self::Error> {
        Ok(self
            .env_impl
            .bytes_copy_to_slice(b, b_pos, slice)
            .unwrap_optimized())
    }

    fn bytes_new_from_slice(&self, slice: &[u8]) -> Result<BytesObject, Self::Error> {
        Ok(self.env_impl.bytes_new_from_slice(slice).unwrap_optimized())
    }

    fn log_from_slice(&self, msg: &str, args: &[Val]) -> Result<Void, Self::Error> {
        Ok(self.env_impl.log_from_slice(msg, args).unwrap_optimized())
    }

    fn string_copy_to_slice(
        &self,
        b: StringObject,
        b_pos: U32Val,
        slice: &mut [u8],
    ) -> Result<(), Self::Error> {
        Ok(self
            .env_impl
            .string_copy_to_slice(b, b_pos, slice)
            .unwrap_optimized())
    }

    fn symbol_copy_to_slice(
        &self,
        b: SymbolObject,
        b_pos: U32Val,
        mem: &mut [u8],
    ) -> Result<(), Self::Error> {
        Ok(self
            .env_impl
            .symbol_copy_to_slice(b, b_pos, mem)
            .unwrap_optimized())
    }

    fn string_new_from_slice(&self, slice: &[u8]) -> Result<StringObject, Self::Error> {
        Ok(self
            .env_impl
            .string_new_from_slice(slice)
            .unwrap_optimized())
    }

    fn symbol_new_from_slice(&self, slice: &[u8]) -> Result<SymbolObject, Self::Error> {
        Ok(self
            .env_impl
            .symbol_new_from_slice(slice)
            .unwrap_optimized())
    }

    fn map_new_from_slices(&self, keys: &[&str], vals: &[Val]) -> Result<MapObject, Self::Error> {
        Ok(self
            .env_impl
            .map_new_from_slices(keys, vals)
            .unwrap_optimized())
    }

    fn map_unpack_to_slice(
        &self,
        map: MapObject,
        keys: &[&str],
        vals: &mut [Val],
    ) -> Result<Void, Self::Error> {
        Ok(self
            .env_impl
            .map_unpack_to_slice(map, keys, vals)
            .unwrap_optimized())
    }

    fn vec_new_from_slice(&self, vals: &[Val]) -> Result<VecObject, Self::Error> {
        Ok(self.env_impl.vec_new_from_slice(vals).unwrap_optimized())
    }

    fn vec_unpack_to_slice(&self, vec: VecObject, vals: &mut [Val]) -> Result<Void, Self::Error> {
        Ok(self
            .env_impl
            .vec_unpack_to_slice(vec, vals)
            .unwrap_optimized())
    }

    fn symbol_index_in_strs(&self, key: Symbol, strs: &[&str]) -> Result<U32Val, Self::Error> {
        Ok(self
            .env_impl
            .symbol_index_in_strs(key, strs)
            .unwrap_optimized())
    }
}

///////////////////////////////////////////////////////////////////////////////
/// X-macro use: impl Env for SDK's Env
///////////////////////////////////////////////////////////////////////////////

// This is a helper macro used only by impl_env_for_sdk below. It consumes a
// token-tree of the form:
//
//  {fn $fn_id:ident $args:tt -> $ret:ty}
//
// and produces the the corresponding method definition to be used in the
// SDK's Env implementation of the Env (calling through to the corresponding
// guest or host implementation).
macro_rules! sdk_function_helper {
    {$mod_id:ident, fn $fn_id:ident($($arg:ident:$type:ty),*) -> $ret:ty}
    =>
    {
        fn $fn_id(&self, $($arg:$type),*) -> Result<$ret, Self::Error> {
            internal::reject_err(&self.env_impl, self.env_impl.$fn_id($($arg),*))
        }
    };
}

// This is a callback macro that pattern-matches the token-tree passed by the
// x-macro (call_macro_with_all_host_functions) and produces a suite of
// forwarding-method definitions, which it places in the body of the declaration
// of the implementation of Env for the SDK's Env.
macro_rules! impl_env_for_sdk {
    {
        $(
            // This outer pattern matches a single 'mod' block of the token-tree
            // passed from the x-macro to this macro. It is embedded in a `$()*`
            // pattern-repetition matcher so that it will match all provided
            // 'mod' blocks provided.
            $(#[$mod_attr:meta])*
            mod $mod_id:ident $mod_str:literal
            {
                $(
                    // This inner pattern matches a single function description
                    // inside a 'mod' block in the token-tree passed from the
                    // x-macro to this macro. It is embedded in a `$()*`
                    // pattern-repetition matcher so that it will match all such
                    // descriptions.
                    $(#[$fn_attr:meta])*
                    { $fn_str:literal, $($min_proto:literal)?, $($max_proto:literal)?, fn $fn_id:ident $args:tt -> $ret:ty }
                )*
            }
        )*
    }

    =>  // The part of the macro above this line is a matcher; below is its expansion.

    {
        // This macro expands to a single item: the implementation of Env for
        // the SDK's Env struct used by client contract code running in a WASM VM.
        #[doc(hidden)]
        impl internal::Env for Env
        {
            $(
                $(
                    // This invokes the guest_function_helper! macro above
                    // passing only the relevant parts of the declaration
                    // matched by the inner pattern above. It is embedded in two
                    // nested `$()*` pattern-repetition expanders that
                    // correspond to the pattern-repetition matchers in the
                    // match section, but we ignore the structure of the 'mod'
                    // block repetition-level from the outer pattern in the
                    // expansion, flattening all functions from all 'mod' blocks
                    // into the implementation of Env for Guest.
                    sdk_function_helper!{$mod_id, fn $fn_id $args -> $ret}
                )*
            )*
        }
    };
}

// Here we invoke the x-macro passing generate_env_trait as its callback macro.
internal::call_macro_with_all_host_functions! { impl_env_for_sdk }