pgrx_macros/

lib.rs

//LICENSE Portions Copyright 2019-2021 ZomboDB, LLC.
//LICENSE
//LICENSE Portions Copyright 2021-2023 Technology Concepts & Design, Inc.
//LICENSE
//LICENSE Portions Copyright 2023-2023 PgCentral Foundation, Inc. <contact@pgcentral.org>
//LICENSE
//LICENSE All rights reserved.
//LICENSE
//LICENSE Use of this source code is governed by the MIT license that can be found in the LICENSE file.
extern crate proc_macro;

use proc_macro::TokenStream;
use std::collections::HashSet;
use std::ffi::CString;

use proc_macro2::Ident;
use quote::{ToTokens, format_ident, quote};
use syn::spanned::Spanned;
use syn::{Attribute, Data, DeriveInput, Item, ItemImpl, parse_macro_input};

use operators::{deriving_postgres_eq, deriving_postgres_hash, deriving_postgres_ord};
use pgrx_sql_entity_graph as sql_gen;
use sql_gen::{
    CodeEnrichment, ExtensionSql, ExtensionSqlFile, ExternArgs, PgAggregate, PgCast, PgExtern,
    PostgresEnum, Schema, parse_extern_attributes,
};

mod operators;
mod rewriter;

/// Declare a function as `#[pg_guard]` to indicate that it is called from a Postgres `extern "C-unwind"`
/// function so that Rust `panic!()`s (and Postgres `elog(ERROR)`s) will be properly handled by `pgrx`
#[proc_macro_attribute]
pub fn pg_guard(attr: TokenStream, item: TokenStream) -> TokenStream {
    // get a usable token stream
    let ast = parse_macro_input!(item as syn::Item);

    let res = match ast {
        // this is for processing the members of extern "C-unwind" { } blocks
        // functions inside the block get wrapped as public, top-level unsafe functions that are not "extern"
        Item::ForeignMod(block) => Ok(rewriter::extern_block(block)),

        // process top-level functions
        Item::Fn(func) => rewriter::item_fn_without_rewrite(func, attr),
        unknown => Err(syn::Error::new(
            unknown.span(),
            "#[pg_guard] can only be applied to extern \"C-unwind\" blocks and top-level functions",
        )),
    };
    res.unwrap_or_else(|e| e.into_compile_error()).into()
}

/// `#[pg_test]` functions are test functions (akin to `#[test]`), but they run in-process inside
/// Postgres during `cargo pgrx test`.
///
/// This can be combined with test attributes like [`#[should_panic(expected = "..")]`][expected].
///
/// [expected]: https://doc.rust-lang.org/reference/attributes/testing.html#the-should_panic-attribute
#[proc_macro_attribute]
pub fn pg_test(attr: TokenStream, item: TokenStream) -> TokenStream {
    let mut stream = proc_macro2::TokenStream::new();
    let args = parse_extern_attributes(proc_macro2::TokenStream::from(attr.clone()));

    let mut expected_error = None;
    args.into_iter().for_each(|v| {
        if let ExternArgs::ShouldPanic(message) = v {
            expected_error = Some(message)
        }
    });

    let ast = parse_macro_input!(item as syn::Item);

    match ast {
        Item::Fn(mut func) => {
            // Here we need to break out attributes into test and non-test attributes,
            // so the generated #[test] attributes are in the appropriate place.
            let (test_attributes, non_test_attributes) =
                func.attrs.into_iter().partition::<Vec<Attribute>, _>(|attr| {
                    attr.path()
                        .get_ident()
                        .is_some_and(|ident| ident == "ignore" || ident == "should_panic")
                });

            func.attrs = non_test_attributes;

            stream.extend(proc_macro2::TokenStream::from(pg_extern(
                attr,
                Item::Fn(func.clone()).to_token_stream().into(),
            )));

            let expected_error = match expected_error {
                Some(msg) => quote! {Some(#msg)},
                None => quote! {None},
            };

            let sql_funcname = func.sig.ident.to_string();
            let test_func_name = format_ident!("pg_{}", func.sig.ident);

            let attributes = func.attrs;
            let mut att_stream = proc_macro2::TokenStream::new();

            for a in attributes.iter() {
                let as_str = a.to_token_stream().to_string();
                att_stream.extend(quote! {
                    options.push(#as_str);
                });
            }

            stream.extend(quote! {
                #[test]
                #(#test_attributes)*
                fn #test_func_name() {
                    let mut options = Vec::new();
                    #att_stream

                    crate::pg_test::setup(options);
                    let res = pgrx_tests::run_test(#sql_funcname, #expected_error, crate::pg_test::postgresql_conf_options());
                    match res {
                        Ok(()) => (),
                        Err(e) => panic!("{e:?}")
                    }
                }
            });
        }

        thing => {
            return syn::Error::new(
                thing.span(),
                "#[pg_test] can only be applied to top-level functions",
            )
            .into_compile_error()
            .into();
        }
    }

    stream.into()
}

/// Associated macro for `#[pg_test]` to provide context back to your test framework to indicate
/// that the test system is being initialized
#[proc_macro_attribute]
pub fn initialize(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/**
Declare a function as `#[pg_cast]` to indicate that it represents a Postgres [cast](https://www.postgresql.org/docs/current/sql-createcast.html).

* `assignment`: Corresponds to [`AS ASSIGNMENT`](https://www.postgresql.org/docs/current/sql-createcast.html).
* `implicit`: Corresponds to [`AS IMPLICIT`](https://www.postgresql.org/docs/current/sql-createcast.html).

By default if no attribute is specified, the cast function can only be used in an explicit cast.

Functions MUST accept and return exactly one value whose type MUST be a `pgrx` supported type. `pgrx` supports many PostgreSQL types by default.
New types can be defined via [`macro@PostgresType`] or [`macro@PostgresEnum`].

`#[pg_cast]` also supports all the attributes supported by the [`macro@pg_extern]` macro, which are
passed down to the underlying function.

Example usage:
```rust,ignore
use pgrx::*;
#[pg_cast(implicit)]
fn cast_json_to_int(input: Json) -> i32 { todo!() }
*/
#[proc_macro_attribute]
pub fn pg_cast(attr: TokenStream, item: TokenStream) -> TokenStream {
    fn wrapped(attr: TokenStream, item: TokenStream) -> Result<TokenStream, syn::Error> {
        use syn::parse::Parser;
        use syn::punctuated::Punctuated;

        let mut cast = None;
        let mut pg_extern_attrs = proc_macro2::TokenStream::new();

        // look for the attributes `#[pg_cast]` directly understands
        match Punctuated::<syn::Path, syn::Token![,]>::parse_terminated.parse(attr) {
            Ok(paths) => {
                let mut new_paths = Punctuated::<syn::Path, syn::Token![,]>::new();
                for path in paths {
                    match (PgCast::try_from(path), &cast) {
                        (Ok(style), None) => cast = Some(style),
                        (Ok(_), Some(cast)) => {
                            panic!("The cast type has already been set to `{cast:?}`")
                        }

                        // ... and anything it doesn't understand is blindly passed through to the
                        // underlying `#[pg_extern]` function that gets created, which will ultimately
                        // decide what's naughty and what's nice
                        (Err(unknown), _) => {
                            new_paths.push(unknown);
                        }
                    }
                }

                pg_extern_attrs.extend(new_paths.into_token_stream());
            }
            Err(err) => {
                panic!("Failed to parse attribute to pg_cast: {err}")
            }
        }

        let pg_extern = PgExtern::new(pg_extern_attrs, item.clone().into())?.0;
        Ok(CodeEnrichment(pg_extern.as_cast(cast.unwrap_or_default())).to_token_stream().into())
    }

    wrapped(attr, item).unwrap_or_else(|e: syn::Error| e.into_compile_error().into())
}

/// Declare a function as `#[pg_operator]` to indicate that it represents a Postgres operator
/// `cargo pgrx schema` will automatically generate the underlying SQL
#[proc_macro_attribute]
pub fn pg_operator(attr: TokenStream, item: TokenStream) -> TokenStream {
    pg_extern(attr, item)
}

/// Used with `#[pg_operator]`.  1 value which is the operator name itself
#[proc_macro_attribute]
pub fn opname(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn commutator(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn negator(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn restrict(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  1 value which is the function name
#[proc_macro_attribute]
pub fn join(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  no values
#[proc_macro_attribute]
pub fn hashes(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/// Used with `#[pg_operator]`.  no values
#[proc_macro_attribute]
pub fn merges(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/**
Declare a Rust module and its contents to be in a schema.

The schema name will always be the `mod`'s identifier. So `mod flop` will create a `flop` schema.

If there is a schema inside a schema, the most specific schema is chosen.

In this example, the created `example` function is in the `dsl_filters` schema.

```rust,ignore
use pgrx::*;

#[pg_schema]
mod dsl {
    use pgrx::*;
    #[pg_schema]
    mod dsl_filters {
        use pgrx::*;
        #[pg_extern]
        fn example() { todo!() }
    }
}
```

File modules (like `mod name;`) aren't able to be supported due to [`rust/#54725`](https://github.com/rust-lang/rust/issues/54725).

*/
#[proc_macro_attribute]
pub fn pg_schema(_attr: TokenStream, input: TokenStream) -> TokenStream {
    fn wrapped(input: TokenStream) -> Result<TokenStream, syn::Error> {
        let pgrx_schema: Schema = syn::parse(input)?;
        Ok(pgrx_schema.to_token_stream().into())
    }

    wrapped(input).unwrap_or_else(|e: syn::Error| e.into_compile_error().into())
}

/**
Declare SQL to be included in generated extension script.

Accepts a String literal, a `name` attribute, and optionally others:

* `name = "item"`: Set the unique identifier to `"item"` for use in `requires` declarations.
* `requires = [item, item_two]`: References to other `name`s or Rust items which this SQL should be present after.
* `creates = [ Type(submod::Cust), Enum(Pre), Function(defined)]`: Communicates that this SQL block creates certain entities.
  Please note it **does not** create matching Rust types.
* `bootstrap` (**Unique**): Communicates that this is SQL intended to go before all other generated SQL.
* `finalize` (**Unique**): Communicates that this is SQL intended to go after all other generated SQL.

You can declare some SQL without any positioning information, meaning it can end up anywhere in the generated SQL:

```rust,ignore
use pgrx_macros::extension_sql;

extension_sql!(
    r#"
    -- SQL statements
    "#,
    name = "demo",
);
```

To cause the SQL to be output at the start of the generated SQL:

```rust,ignore
use pgrx_macros::extension_sql;

extension_sql!(
    r#"
    -- SQL statements
    "#,
    name = "demo",
    bootstrap,
);
```

To cause the SQL to be output at the end of the generated SQL:

```rust,ignore
use pgrx_macros::extension_sql;

extension_sql!(
    r#"
    -- SQL statements
    "#,
    name = "demo",
    finalize,
);
```

To declare the SQL dependent, or a dependency of, other items:

```rust,ignore
use pgrx_macros::extension_sql;

struct Treat;

mod dog_characteristics {
    enum DogAlignment {
        Good
    }
}

extension_sql!(r#"
    -- SQL statements
    "#,
    name = "named_one",
);

extension_sql!(r#"
    -- SQL statements
    "#,
    name = "demo",
    requires = [ "named_one", dog_characteristics::DogAlignment ],
);
```

To declare the SQL defines some entity (**Caution:** This is not recommended usage):

```rust,ignore
use pgrx::stringinfo::StringInfo;
use pgrx::*;
use pgrx_utils::get_named_capture;

#[derive(Debug)]
#[repr(C)]
struct Complex {
    x: f64,
    y: f64,
}

extension_sql!(r#"\
        CREATE TYPE complex;\
    "#,
    name = "create_complex_type",
    creates = [Type(Complex)],
);

#[pg_extern(immutable)]
fn complex_in(input: &core::ffi::CStr) -> PgBox<Complex> {
    todo!()
}

#[pg_extern(immutable)]
fn complex_out(complex: PgBox<Complex>) -> &'static ::core::ffi::CStr {
    todo!()
}

extension_sql!(r#"\
        CREATE TYPE complex (
            internallength = 16,
            input = complex_in,
            output = complex_out,
            alignment = double
        );\
    "#,
    name = "demo",
    requires = ["create_complex_type", complex_in, complex_out],
);

```
*/
#[proc_macro]
pub fn extension_sql(input: TokenStream) -> TokenStream {
    fn wrapped(input: TokenStream) -> Result<TokenStream, syn::Error> {
        let ext_sql: CodeEnrichment<ExtensionSql> = syn::parse(input)?;
        Ok(ext_sql.to_token_stream().into())
    }

    wrapped(input).unwrap_or_else(|e: syn::Error| e.into_compile_error().into())
}

/**
Declare SQL (from a file) to be included in generated extension script.

Accepts the same options as [`macro@extension_sql`]. `name` is automatically set to the file name (not the full path).

You can declare some SQL without any positioning information, meaning it can end up anywhere in the generated SQL:

```rust,ignore
use pgrx_macros::extension_sql_file;
extension_sql_file!(
    "../static/demo.sql",
);
```

To override the default name:

```rust,ignore
use pgrx_macros::extension_sql_file;

extension_sql_file!(
    "../static/demo.sql",
    name = "singular",
);
```

For all other options, and examples of them, see [`macro@extension_sql`].
*/
#[proc_macro]
pub fn extension_sql_file(input: TokenStream) -> TokenStream {
    fn wrapped(input: TokenStream) -> Result<TokenStream, syn::Error> {
        let ext_sql: CodeEnrichment<ExtensionSqlFile> = syn::parse(input)?;
        Ok(ext_sql.to_token_stream().into())
    }

    wrapped(input).unwrap_or_else(|e: syn::Error| e.into_compile_error().into())
}

/// Associated macro for `#[pg_extern]` or `#[macro@pg_operator]`.  Used to set the `SEARCH_PATH` option
/// on the `CREATE FUNCTION` statement.
#[proc_macro_attribute]
pub fn search_path(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/**
Declare a function as `#[pg_extern]` to indicate that it can be used by Postgres as a UDF.

Optionally accepts the following attributes:

* `immutable`: Corresponds to [`IMMUTABLE`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `strict`: Corresponds to [`STRICT`](https://www.postgresql.org/docs/current/sql-createfunction.html).
  + In most cases, `#[pg_extern]` can detect when no `Option<T>`s are used, and automatically set this.
* `stable`: Corresponds to [`STABLE`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `volatile`: Corresponds to [`VOLATILE`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `raw`: Corresponds to [`RAW`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `support`: Corresponds to [`SUPPORT`](https://www.postgresql.org/docs/current/sql-createfunction.html) and is the Rust path to a function to act as the SUPPORT function
* `security_definer`: Corresponds to [`SECURITY DEFINER`](https://www.postgresql.org/docs/current/sql-createfunction.html)
* `security_invoker`: Corresponds to [`SECURITY INVOKER`](https://www.postgresql.org/docs/current/sql-createfunction.html)
* `parallel_safe`: Corresponds to [`PARALLEL SAFE`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `parallel_unsafe`: Corresponds to [`PARALLEL UNSAFE`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `parallel_restricted`: Corresponds to [`PARALLEL RESTRICTED`](https://www.postgresql.org/docs/current/sql-createfunction.html).
* `no_guard`: Do not use `#[pg_guard]` with the function.
* `sql`: Same arguments as [`#[pgrx(sql = ..)]`](macro@pgrx).
* `name`: Specifies target function name. Defaults to Rust function name.

Functions can accept and return any type which `pgrx` supports. `pgrx` supports many PostgreSQL types by default.
New types can be defined via [`macro@PostgresType`] or [`macro@PostgresEnum`].


Without any arguments or returns:
```rust,ignore
use pgrx::*;
#[pg_extern]
fn foo() { todo!() }
```

# Arguments
It's possible to pass even complex arguments:

```rust,ignore
use pgrx::*;
#[pg_extern]
fn boop(
    a: i32,
    b: Option<i32>,
    c: Vec<i32>,
    d: Option<Vec<Option<i32>>>
) { todo!() }
```

It's possible to set argument defaults, set by PostgreSQL when the function is invoked:

```rust,ignore
use pgrx::*;
#[pg_extern]
fn boop(a: default!(i32, 11111)) { todo!() }
#[pg_extern]
fn doop(
    a: default!(Vec<Option<&str>>, "ARRAY[]::text[]"),
    b: default!(String, "'note the inner quotes!'")
) { todo!() }
```

The `default!()` macro may only be used in argument position.

It accepts 2 arguments:

* A type
* A `bool`, numeric, or SQL string to represent the default. `"NULL"` is a possible value, as is `"'string'"`

**If the default SQL entity created by the extension:** ensure it is added to `requires` as a dependency:

```rust,ignore
use pgrx::*;
#[pg_extern]
fn default_value() -> i32 { todo!() }

#[pg_extern(
    requires = [ default_value, ],
)]
fn do_it(
    a: default!(i32, "default_value()"),
) { todo!() }
```

# Returns

It's possible to return even complex values, as well:

```rust,ignore
use pgrx::*;
#[pg_extern]
fn boop() -> i32 { todo!() }
#[pg_extern]
fn doop() -> Option<i32> { todo!() }
#[pg_extern]
fn swoop() -> Option<Vec<Option<i32>>> { todo!() }
#[pg_extern]
fn floop() -> (i32, i32) { todo!() }
```

Like in PostgreSQL, it's possible to return tables using iterators and the `name!()` macro:

```rust,ignore
use pgrx::*;
#[pg_extern]
fn floop<'a>() -> TableIterator<'a, (name!(a, i32), name!(b, i32))> {
    TableIterator::new(None.into_iter())
}

#[pg_extern]
fn singular_floop() -> (name!(a, i32), name!(b, i32)) {
    todo!()
}
```

The `name!()` macro may only be used in return position inside the `T` of a `TableIterator<'a, T>`.

It accepts 2 arguments:

* A name, such as `example`
* A type

# Special Cases

`pg_sys::Oid` is a special cased type alias, in order to use it as an argument or return it must be
passed with it's full module path (`pg_sys::Oid`) in order to be resolved.

```rust,ignore
use pgrx::*;

#[pg_extern]
fn example_arg(animals: pg_sys::Oid) {
    todo!()
}

#[pg_extern]
fn example_return() -> pg_sys::Oid {
    todo!()
}
```

*/
#[proc_macro_attribute]
#[track_caller]
pub fn pg_extern(attr: TokenStream, item: TokenStream) -> TokenStream {
    fn wrapped(attr: TokenStream, item: TokenStream) -> Result<TokenStream, syn::Error> {
        let pg_extern_item = PgExtern::new(attr.into(), item.into())?;
        Ok(pg_extern_item.to_token_stream().into())
    }

    wrapped(attr, item).unwrap_or_else(|e: syn::Error| e.into_compile_error().into())
}

/**
Generate necessary bindings for using the enum with PostgreSQL.

```rust,ignore
# use pgrx_pg_sys as pg_sys;
use pgrx::*;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize, PostgresEnum)]
enum DogNames {
    Nami,
    Brandy,
}
```

*/
#[proc_macro_derive(PostgresEnum, attributes(requires, pgrx))]
pub fn postgres_enum(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_postgres_enum(ast).unwrap_or_else(|e| e.into_compile_error()).into()
}

fn impl_postgres_enum(ast: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    let mut stream = proc_macro2::TokenStream::new();
    let sql_graph_entity_ast = ast.clone();
    let generics = &ast.generics.clone();
    let enum_ident = &ast.ident;
    let enum_name = enum_ident.to_string();

    // validate that we're only operating on an enum
    let Data::Enum(enum_data) = ast.data else {
        return Err(syn::Error::new(
            ast.span(),
            "#[derive(PostgresEnum)] can only be applied to enums",
        ));
    };

    let mut from_datum = proc_macro2::TokenStream::new();
    let mut into_datum = proc_macro2::TokenStream::new();

    for d in enum_data.variants.clone() {
        let label_ident = &d.ident;
        let label_string = label_ident.to_string();

        from_datum.extend(quote! { #label_string => Some(#enum_ident::#label_ident), });
        into_datum.extend(quote! { #enum_ident::#label_ident => Some(::pgrx::enum_helper::lookup_enum_by_label(#enum_name, #label_string)), });
    }

    // We need another variant of the params for the ArgAbi impl
    let fcx_lt = syn::Lifetime::new("'fcx", proc_macro2::Span::mixed_site());
    let mut generics_with_fcx = generics.clone();
    // so that we can bound on Self: 'fcx
    generics_with_fcx.make_where_clause().predicates.push(syn::WherePredicate::Type(
        syn::PredicateType {
            lifetimes: None,
            bounded_ty: syn::parse_quote! { Self },
            colon_token: syn::Token![:](proc_macro2::Span::mixed_site()),
            bounds: syn::parse_quote! { #fcx_lt },
        },
    ));
    let (impl_gens, ty_gens, where_clause) = generics_with_fcx.split_for_impl();
    let mut impl_gens: syn::Generics = syn::parse_quote! { #impl_gens };
    impl_gens
        .params
        .insert(0, syn::GenericParam::Lifetime(syn::LifetimeParam::new(fcx_lt.clone())));

    stream.extend(quote! {
        impl ::pgrx::datum::FromDatum for #enum_ident {
            #[inline]
            unsafe fn from_polymorphic_datum(datum: ::pgrx::pg_sys::Datum, is_null: bool, _typeoid: ::pgrx::pg_sys::Oid) -> Option<#enum_ident> {
                if is_null {
                    None
                } else {
                    // GREPME: non-primitive cast u64 as Oid
                    let (name, _, _) = ::pgrx::enum_helper::lookup_enum_by_oid(unsafe { ::pgrx::pg_sys::Oid::from_datum(datum, is_null)? } );
                    match name.as_str() {
                        #from_datum
                        _ => panic!("invalid enum value: {name}")
                    }
                }
            }
        }

        unsafe impl #impl_gens ::pgrx::callconv::ArgAbi<#fcx_lt> for #enum_ident #ty_gens #where_clause {
            unsafe fn unbox_arg_unchecked(arg: ::pgrx::callconv::Arg<'_, #fcx_lt>) -> Self {
                let index = arg.index();
                unsafe { arg.unbox_arg_using_from_datum().unwrap_or_else(|| panic!("argument {index} must not be null")) }
            }

        }

        unsafe impl #generics ::pgrx::datum::UnboxDatum for #enum_ident #generics {
            type As<'dat> = #enum_ident #generics where Self: 'dat;
            #[inline]
            unsafe fn unbox<'dat>(d: ::pgrx::datum::Datum<'dat>) -> Self::As<'dat> where Self: 'dat {
                <Self as ::pgrx::datum::FromDatum>::from_datum(::core::mem::transmute(d), false).unwrap()
            }
        }

        impl ::pgrx::datum::IntoDatum for #enum_ident {
            #[inline]
            fn into_datum(self) -> Option<::pgrx::pg_sys::Datum> {
                match self {
                    #into_datum
                }
            }

            fn type_oid() -> ::pgrx::pg_sys::Oid {
                ::pgrx::wrappers::regtypein(#enum_name)
            }

        }

        unsafe impl ::pgrx::callconv::BoxRet for #enum_ident {
            unsafe fn box_into<'fcx>(self, fcinfo: &mut ::pgrx::callconv::FcInfo<'fcx>) -> ::pgrx::datum::Datum<'fcx> {
                match ::pgrx::datum::IntoDatum::into_datum(self) {
                    None => fcinfo.return_null(),
                    Some(datum) => unsafe { fcinfo.return_raw_datum(datum) },
                }
            }
        }
    });

    let sql_graph_entity_item = PostgresEnum::from_derive_input(sql_graph_entity_ast)?;
    sql_graph_entity_item.to_tokens(&mut stream);

    Ok(stream)
}

/**
Generate necessary bindings for using the type with PostgreSQL.

```rust,ignore
# use pgrx_pg_sys as pg_sys;
use pgrx::*;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize, PostgresType)]
struct Dog {
    treats_received: i64,
    pets_gotten: i64,
}

#[derive(Debug, Serialize, Deserialize, PostgresType)]
enum Animal {
    Dog(Dog),
}
```

Optionally accepts the following attributes:

* `inoutfuncs(some_in_fn, some_out_fn)`: Define custom in/out functions for the type.
* `pgvarlena_inoutfuncs(some_in_fn, some_out_fn)`: Define custom in/out functions for the `PgVarlena` of this type.
* `pg_binary_protocol`: Use the binary protocol for this type.
* `pgrx(alignment = "<align>")`: Derive Postgres alignment from Rust type. One of `"on"`, or `"off"`.
* `sql`: Same arguments as [`#[pgrx(sql = ..)]`](macro@pgrx).
*/
#[proc_macro_derive(
    PostgresType,
    attributes(
        inoutfuncs,
        pgvarlena_inoutfuncs,
        pg_binary_protocol,
        bikeshed_postgres_type_manually_impl_from_into_datum,
        requires,
        pgrx
    )
)]
pub fn postgres_type(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_postgres_type(ast).unwrap_or_else(|e| e.into_compile_error()).into()
}

fn impl_postgres_type(ast: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    let name = &ast.ident;
    let generics = &ast.generics.clone();
    let has_lifetimes = generics.lifetimes().next();
    let funcname_in = Ident::new(&format!("{name}_in").to_lowercase(), name.span());
    let funcname_out = Ident::new(&format!("{name}_out").to_lowercase(), name.span());
    let funcname_recv = Ident::new(&format!("{name}_recv").to_lowercase(), name.span());
    let funcname_send = Ident::new(&format!("{name}_send").to_lowercase(), name.span());

    let mut args = parse_postgres_type_args(&ast.attrs);
    let mut stream = proc_macro2::TokenStream::new();

    // validate that we're only operating on a struct
    match ast.data {
        Data::Struct(_) => { /* this is okay */ }
        Data::Enum(_) => {
            // this is okay and if there's an attempt to implement PostgresEnum,
            // it will result in compile-time error of conflicting implementation
            // of traits (IntoDatum, inout, etc.)
        }
        _ => {
            return Err(syn::Error::new(
                ast.span(),
                "#[derive(PostgresType)] can only be applied to structs or enums",
            ));
        }
    }

    if !args.contains(&PostgresTypeAttribute::InOutFuncs)
        && !args.contains(&PostgresTypeAttribute::PgVarlenaInOutFuncs)
    {
        // assume the user wants us to implement the InOutFuncs
        args.insert(PostgresTypeAttribute::Default);
    }

    let lifetime = match has_lifetimes {
        Some(lifetime) => quote! {#lifetime},
        None => quote! {'_},
    };

    // We need another variant of the params for the ArgAbi impl
    let fcx_lt = syn::Lifetime::new("'fcx", proc_macro2::Span::mixed_site());
    let mut generics_with_fcx = generics.clone();
    // so that we can bound on Self: 'fcx
    generics_with_fcx.make_where_clause().predicates.push(syn::WherePredicate::Type(
        syn::PredicateType {
            lifetimes: None,
            bounded_ty: syn::parse_quote! { Self },
            colon_token: syn::Token![:](proc_macro2::Span::mixed_site()),
            bounds: syn::parse_quote! { #fcx_lt },
        },
    ));
    let (impl_gens, ty_gens, where_clause) = generics_with_fcx.split_for_impl();
    let mut impl_gens: syn::Generics = syn::parse_quote! { #impl_gens };
    impl_gens
        .params
        .insert(0, syn::GenericParam::Lifetime(syn::LifetimeParam::new(fcx_lt.clone())));

    // all #[derive(PostgresType)] need to implement that trait
    // and also the FromDatum and IntoDatum
    stream.extend(quote! {
        impl #generics ::pgrx::datum::PostgresType for #name #generics { }
    });

    if !args.contains(&PostgresTypeAttribute::ManualFromIntoDatum) {
        stream.extend(
            quote! {
                impl #generics ::pgrx::datum::IntoDatum for #name #generics {
                    fn into_datum(self) -> Option<::pgrx::pg_sys::Datum> {
                        #[allow(deprecated)]
                        Some(unsafe { ::pgrx::datum::cbor_encode(&self) }.into())
                    }

                    fn type_oid() -> ::pgrx::pg_sys::Oid {
                        ::pgrx::wrappers::rust_regtypein::<Self>()
                    }
                }

                unsafe impl #generics ::pgrx::callconv::BoxRet for #name #generics {
                    unsafe fn box_into<'fcx>(self, fcinfo: &mut ::pgrx::callconv::FcInfo<'fcx>) -> ::pgrx::datum::Datum<'fcx> {
                        match ::pgrx::datum::IntoDatum::into_datum(self) {
                            None => fcinfo.return_null(),
                            Some(datum) => unsafe { fcinfo.return_raw_datum(datum) },
                        }
                    }
                }

                impl #generics ::pgrx::datum::FromDatum for #name #generics {
                    unsafe fn from_polymorphic_datum(
                        datum: ::pgrx::pg_sys::Datum,
                        is_null: bool,
                        _typoid: ::pgrx::pg_sys::Oid,
                    ) -> Option<Self> {
                        if is_null {
                            None
                        } else {
                            #[allow(deprecated)]
                            ::pgrx::datum::cbor_decode(datum.cast_mut_ptr())
                        }
                    }

                    unsafe fn from_datum_in_memory_context(
                        mut memory_context: ::pgrx::memcxt::PgMemoryContexts,
                        datum: ::pgrx::pg_sys::Datum,
                        is_null: bool,
                        _typoid: ::pgrx::pg_sys::Oid,
                    ) -> Option<Self> {
                        if is_null {
                            None
                        } else {
                            memory_context.switch_to(|_| {
                                // this gets the varlena Datum copied into this memory context
                                let varlena = ::pgrx::pg_sys::pg_detoast_datum_copy(datum.cast_mut_ptr());
                                <Self as ::pgrx::datum::FromDatum>::from_datum(varlena.into(), is_null)
                            })
                        }
                    }
                }

                unsafe impl #generics ::pgrx::datum::UnboxDatum for #name #generics {
                    type As<'dat> = Self where Self: 'dat;
                    unsafe fn unbox<'dat>(datum: ::pgrx::datum::Datum<'dat>) -> Self::As<'dat> where Self: 'dat {
                        <Self as ::pgrx::datum::FromDatum>::from_datum(::core::mem::transmute(datum), false).unwrap()
                    }
                }

                unsafe impl #impl_gens ::pgrx::callconv::ArgAbi<#fcx_lt> for #name #ty_gens #where_clause
                {
                        unsafe fn unbox_arg_unchecked(arg: ::pgrx::callconv::Arg<'_, #fcx_lt>) -> Self {
                        let index = arg.index();
                        unsafe { arg.unbox_arg_using_from_datum().unwrap_or_else(|| panic!("argument {index} must not be null")) }
                    }
                }
            }
        )
    }

    // and if we don't have custom inout/funcs, we use the JsonInOutFuncs trait
    // which implements _in and _out #[pg_extern] functions that just return the type itself
    if args.contains(&PostgresTypeAttribute::Default) {
        stream.extend(quote! {
            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable, parallel_safe)]
            pub fn #funcname_in #generics(input: Option<&#lifetime ::core::ffi::CStr>) -> Option<#name #generics> {
                use ::pgrx::inoutfuncs::json_from_slice;
                input.map(|cstr| json_from_slice(cstr.to_bytes()).ok()).flatten()
            }

            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern (immutable, parallel_safe)]
            pub fn #funcname_out #generics(input: #name #generics) -> ::pgrx::ffi::CString {
                use ::pgrx::inoutfuncs::json_to_vec;
                let mut bytes = json_to_vec(&input).unwrap();
                bytes.push(0); // terminate
                ::pgrx::ffi::CString::from_vec_with_nul(bytes).unwrap()
            }
        });
    } else if args.contains(&PostgresTypeAttribute::InOutFuncs) {
        // otherwise if it's InOutFuncs our _in/_out functions use an owned type instance
        stream.extend(quote! {
            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable,parallel_safe)]
            pub fn #funcname_in #generics(input: Option<&::core::ffi::CStr>) -> Option<#name #generics> {
                input.map_or_else(|| {
                    if let Some(m) = <#name as ::pgrx::inoutfuncs::InOutFuncs>::NULL_ERROR_MESSAGE {
                        ::pgrx::pg_sys::error!("{m}");
                    }
                    None
                }, |i| Some(<#name as ::pgrx::inoutfuncs::InOutFuncs>::input(i)))
            }

            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable,parallel_safe)]
            pub fn #funcname_out #generics(input: #name #generics) -> ::pgrx::ffi::CString {
                let mut buffer = ::pgrx::stringinfo::StringInfo::new();
                ::pgrx::inoutfuncs::InOutFuncs::output(&input, &mut buffer);
                // SAFETY: We just constructed this StringInfo ourselves
                unsafe { buffer.leak_cstr().to_owned() }
            }
        });
    } else if args.contains(&PostgresTypeAttribute::PgVarlenaInOutFuncs) {
        // otherwise if it's PgVarlenaInOutFuncs our _in/_out functions use a PgVarlena
        stream.extend(quote! {
            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable,parallel_safe)]
            pub fn #funcname_in #generics(input: Option<&::core::ffi::CStr>) -> Option<::pgrx::datum::PgVarlena<#name #generics>> {
                input.map_or_else(|| {
                    if let Some(m) = <#name as ::pgrx::inoutfuncs::PgVarlenaInOutFuncs>::NULL_ERROR_MESSAGE {
                        ::pgrx::pg_sys::error!("{m}");
                    }
                    None
                }, |i| Some(<#name as ::pgrx::inoutfuncs::PgVarlenaInOutFuncs>::input(i)))
            }

            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable,parallel_safe)]
            pub fn #funcname_out #generics(input: ::pgrx::datum::PgVarlena<#name #generics>) -> ::pgrx::ffi::CString {
                let mut buffer = ::pgrx::stringinfo::StringInfo::new();
                ::pgrx::inoutfuncs::PgVarlenaInOutFuncs::output(&*input, &mut buffer);
                // SAFETY: We just constructed this StringInfo ourselves
                unsafe { buffer.leak_cstr().to_owned() }
            }
        });
    }

    if args.contains(&PostgresTypeAttribute::PgBinaryProtocol) {
        // At this time, the `PostgresTypeAttribute` does not impact the way we generate
        // the `recv` and `send` functions.
        stream.extend(quote! {
            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable, strict, parallel_safe)]
            pub fn #funcname_recv #generics(
                mut internal: ::pgrx::datum::Internal,
            ) -> #name #generics {
                let buf = unsafe { internal.get_mut::<::pgrx::pg_sys::StringInfoData>().unwrap() };

                let mut serialized = ::pgrx::StringInfo::new();

                serialized.push_bytes(&[0u8; ::pgrx::pg_sys::VARHDRSZ]); // reserve space for the header
                serialized.push_bytes(unsafe {
                    core::slice::from_raw_parts(
                        buf.data as *const u8,
                        buf.len as usize
                    )
                });

                let size = serialized.len();
                let varlena = serialized.into_char_ptr();

                unsafe{
                    ::pgrx::set_varsize_4b(varlena as *mut ::pgrx::pg_sys::varlena, size as i32);
                    buf.cursor = buf.len;
                    ::pgrx::datum::cbor_decode(varlena as *mut ::pgrx::pg_sys::varlena)
                }
            }
            #[doc(hidden)]
            #[::pgrx::pgrx_macros::pg_extern(immutable, strict, parallel_safe)]
            pub fn #funcname_send #generics(input: #name #generics) -> Vec<u8> {
                use ::pgrx::datum::{FromDatum, IntoDatum};
                let Some(datum): Option<::pgrx::pg_sys::Datum> = input.into_datum() else {
                    ::pgrx::error!("Datum of type `{}` is unexpectedly NULL.", stringify!(#name));
                };
                unsafe {
                    let Some(serialized): Option<Vec<u8>> = FromDatum::from_datum(datum, false) else {
                        ::pgrx::error!("Failed to CBOR-serialize Datum to type `{}`.", stringify!(#name));
                    };
                    serialized
                }
            }
        });
    }

    let sql_graph_entity_item = sql_gen::PostgresTypeDerive::from_derive_input(
        ast,
        args.contains(&PostgresTypeAttribute::PgBinaryProtocol),
    )?;
    sql_graph_entity_item.to_tokens(&mut stream);

    Ok(stream)
}

/// Derives the `GucEnum` trait, so that normal Rust enums can be used as a GUC.
#[proc_macro_derive(PostgresGucEnum, attributes(name, hidden))]
pub fn postgres_guc_enum(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_guc_enum(ast).unwrap_or_else(|e| e.into_compile_error()).into()
}

fn impl_guc_enum(ast: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    use std::str::FromStr;
    use syn::parse::Parse;

    enum GucEnumAttribute {
        Name(CString),
        Hidden(bool),
    }

    impl GucEnumAttribute {
        fn is_guc_enum_attribute(attribute: &str) -> bool {
            matches!(attribute, "name" | "hidden")
        }
    }

    impl Parse for GucEnumAttribute {
        fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
            let ident: Ident = input.parse()?;
            let _: syn::token::Eq = input.parse()?;
            match ident.to_string().as_str() {
                "name" => input.parse::<syn::LitCStr>().map(|val| Self::Name(val.value())),
                "hidden" => input.parse::<syn::LitBool>().map(|val| Self::Hidden(val.value())),
                x => Err(syn::Error::new(input.span(), format!("unknown attribute {x}"))),
            }
        }
    }

    // validate that we're only operating on an enum
    let Data::Enum(data) = ast.data.clone() else {
        return Err(syn::Error::new(
            ast.span(),
            "#[derive(PostgresGucEnum)] can only be applied to enums",
        ));
    };
    let ident = ast.ident.clone();
    let mut config = Vec::new();
    for (index, variant) in data.variants.iter().enumerate() {
        let default_name = CString::from_str(&variant.ident.to_string())
            .expect("the identifier contains a null character.");
        let default_val = index as i32;
        let default_hidden = false;
        let mut name = None;
        let mut hidden = None;

        for attr in variant.attrs.iter() {
            if let Some(ident) = attr.path().get_ident()
                && GucEnumAttribute::is_guc_enum_attribute(&ident.to_string())
            {
                let pair: GucEnumAttribute = syn::parse2(attr.meta.to_token_stream())?;
                match pair {
                    GucEnumAttribute::Name(value) => {
                        if name.replace(value).is_some() {
                            return Err(syn::Error::new(ast.span(), "too many #[name] attributes"));
                        }
                    }
                    GucEnumAttribute::Hidden(value) => {
                        if hidden.replace(value).is_some() {
                            return Err(syn::Error::new(
                                ast.span(),
                                "too many #[hidden] attributes",
                            ));
                        }
                    }
                }
            }
        }
        let ident = variant.ident.clone();
        let name = name.unwrap_or(default_name);
        let val = default_val;
        let hidden = hidden.unwrap_or(default_hidden);
        config.push((ident, name, val, hidden));
    }
    let config_idents = config.iter().map(|x| &x.0).collect::<Vec<_>>();
    let config_names = config.iter().map(|x| &x.1).collect::<Vec<_>>();
    let config_vals = config.iter().map(|x| &x.2).collect::<Vec<_>>();
    let config_hiddens = config.iter().map(|x| &x.3).collect::<Vec<_>>();

    Ok(quote! {
        unsafe impl ::pgrx::guc::GucEnum for #ident {
            fn from_ordinal(ordinal: i32) -> Self {
                match ordinal {
                    #(#config_vals => Self::#config_idents,)*
                    _ => panic!("Unrecognized ordinal"),
                }
            }

            fn to_ordinal(&self) -> i32 {
                match self {
                    #(Self::#config_idents => #config_vals,)*
                }
            }

            const CONFIG_ENUM_ENTRY: *const ::pgrx::pg_sys::config_enum_entry = [
                #(
                    ::pgrx::pg_sys::config_enum_entry {
                        name: #config_names.as_ptr(),
                        val: #config_vals,
                        hidden: #config_hiddens,
                    },
                )*
                ::pgrx::pg_sys::config_enum_entry {
                    name: core::ptr::null(),
                    val: 0,
                    hidden: false,
                },
            ].as_ptr();
        }
    })
}

#[derive(Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
enum PostgresTypeAttribute {
    InOutFuncs,
    PgBinaryProtocol,
    PgVarlenaInOutFuncs,
    Default,
    ManualFromIntoDatum,
}

fn parse_postgres_type_args(attributes: &[Attribute]) -> HashSet<PostgresTypeAttribute> {
    let mut categorized_attributes = HashSet::new();

    for a in attributes {
        let path = &a.path();
        let path = quote! {#path}.to_string();
        match path.as_str() {
            "inoutfuncs" => {
                categorized_attributes.insert(PostgresTypeAttribute::InOutFuncs);
            }
            "pg_binary_protocol" => {
                categorized_attributes.insert(PostgresTypeAttribute::PgBinaryProtocol);
            }
            "pgvarlena_inoutfuncs" => {
                categorized_attributes.insert(PostgresTypeAttribute::PgVarlenaInOutFuncs);
            }
            "bikeshed_postgres_type_manually_impl_from_into_datum" => {
                categorized_attributes.insert(PostgresTypeAttribute::ManualFromIntoDatum);
            }
            _ => {
                // we can just ignore attributes we don't understand
            }
        };
    }

    categorized_attributes
}

/**
Generate necessary code using the type in operators like `==` and `!=`.

```rust,ignore
# use pgrx_pg_sys as pg_sys;
use pgrx::*;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize, PostgresEnum, PartialEq, Eq, PostgresEq)]
enum DogNames {
    Nami,
    Brandy,
}
```
Optionally accepts the following attributes:

* `sql`: Same arguments as [`#[pgrx(sql = ..)]`](macro@pgrx).

# No bounds?
Unlike some derives, this does not implement a "real" Rust trait, thus
PostgresEq cannot be used in trait bounds, nor can it be manually implemented.
*/
#[proc_macro_derive(PostgresEq, attributes(pgrx))]
pub fn derive_postgres_eq(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);
    deriving_postgres_eq(ast).unwrap_or_else(syn::Error::into_compile_error).into()
}

/**
Generate necessary code using the type in operators like `>`, `<`, `<=`, and `>=`.

```rust,ignore
# use pgrx_pg_sys as pg_sys;
use pgrx::*;
use serde::{Deserialize, Serialize};
#[derive(
    Debug, Serialize, Deserialize, PartialEq, Eq,
     PartialOrd, Ord, PostgresEnum, PostgresOrd
)]
enum DogNames {
    Nami,
    Brandy,
}
```
Optionally accepts the following attributes:

* `sql`: Same arguments as [`#[pgrx(sql = ..)]`](macro@pgrx).

# No bounds?
Unlike some derives, this does not implement a "real" Rust trait, thus
PostgresOrd cannot be used in trait bounds, nor can it be manually implemented.
*/
#[proc_macro_derive(PostgresOrd, attributes(pgrx))]
pub fn derive_postgres_ord(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);
    deriving_postgres_ord(ast).unwrap_or_else(syn::Error::into_compile_error).into()
}

/**
Generate necessary code for stable hashing the type so it can be used with `USING hash` indexes.

```rust,ignore
# use pgrx_pg_sys as pg_sys;
use pgrx::*;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Hash, PostgresEnum, PostgresHash)]
enum DogNames {
    Nami,
    Brandy,
}
```
Optionally accepts the following attributes:

* `sql`: Same arguments as [`#[pgrx(sql = ..)]`](macro@pgrx).

# No bounds?
Unlike some derives, this does not implement a "real" Rust trait, thus
PostgresHash cannot be used in trait bounds, nor can it be manually implemented.
*/
#[proc_macro_derive(PostgresHash, attributes(pgrx))]
pub fn derive_postgres_hash(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);
    deriving_postgres_hash(ast).unwrap_or_else(syn::Error::into_compile_error).into()
}

/// Derives the `ToAggregateName` trait.
#[proc_macro_derive(AggregateName, attributes(aggregate_name))]
pub fn derive_aggregate_name(input: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(input as syn::DeriveInput);

    impl_aggregate_name(ast).unwrap_or_else(|e| e.into_compile_error()).into()
}

fn impl_aggregate_name(ast: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    let name = &ast.ident;

    let mut custom_name_value: Option<String> = None;

    for attr in &ast.attrs {
        if attr.path().is_ident("aggregate_name") {
            let meta = &attr.meta;
            match meta {
                syn::Meta::NameValue(syn::MetaNameValue {
                    value: syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Str(s), .. }),
                    ..
                }) => {
                    custom_name_value = Some(s.value());
                    break;
                }
                _ => {
                    return Err(syn::Error::new_spanned(
                        attr,
                        "#[aggregate_name] must be in the form `#[aggregate_name = \"string_literal\"]`",
                    ));
                }
            }
        }
    }

    let name_str = custom_name_value.unwrap_or(name.to_string());

    let expanded = quote! {
        impl ::pgrx::aggregate::ToAggregateName for #name {
            const NAME: &'static str = #name_str;
        }
    };

    Ok(expanded)
}

/**
Declare a `pgrx::Aggregate` implementation on a type as able to used by Postgres as an aggregate.

Functions inside the `impl` may use the [`#[pgrx]`](macro@pgrx) attribute.
*/
#[proc_macro_attribute]
pub fn pg_aggregate(_attr: TokenStream, item: TokenStream) -> TokenStream {
    // We don't care about `_attr` as we can find it in the `ItemMod`.
    fn wrapped(item_impl: ItemImpl) -> Result<TokenStream, syn::Error> {
        let sql_graph_entity_item = PgAggregate::new(item_impl)?;

        Ok(sql_graph_entity_item.to_token_stream().into())
    }

    let parsed_base = parse_macro_input!(item as syn::ItemImpl);
    wrapped(parsed_base).unwrap_or_else(|e| e.into_compile_error().into())
}

/**
A helper attribute for various contexts.

## Usage with [`#[pg_aggregate]`](macro@pg_aggregate).

It can be decorated on functions inside a [`#[pg_aggregate]`](macro@pg_aggregate) implementation.
In this position, it takes the same args as [`#[pg_extern]`](macro@pg_extern), and those args have the same effect.

## Usage for configuring SQL generation

This attribute can be used to control the behavior of the SQL generator on a decorated item,
e.g. `#[pgrx(sql = false)]`

Currently `sql` can be provided one of the following:

* Disable SQL generation with `#[pgrx(sql = false)]`
* Call custom SQL generator function with `#[pgrx(sql = path::to_function)]`
* Render a specific fragment of SQL with a string `#[pgrx(sql = "CREATE FUNCTION ...")]`

*/
#[proc_macro_attribute]
pub fn pgrx(_attr: TokenStream, item: TokenStream) -> TokenStream {
    item
}

/**
Create a [PostgreSQL trigger function](https://www.postgresql.org/docs/current/plpgsql-trigger.html)

Review the `pgrx::trigger_support::PgTrigger` documentation for use.

 */
#[proc_macro_attribute]
pub fn pg_trigger(attrs: TokenStream, input: TokenStream) -> TokenStream {
    fn wrapped(attrs: TokenStream, input: TokenStream) -> Result<TokenStream, syn::Error> {
        use pgrx_sql_entity_graph::{PgTrigger, PgTriggerAttribute};
        use syn::Token;
        use syn::parse::Parser;
        use syn::punctuated::Punctuated;

        let attributes =
            Punctuated::<PgTriggerAttribute, Token![,]>::parse_terminated.parse(attrs)?;
        let item_fn: syn::ItemFn = syn::parse(input)?;
        let trigger_item = PgTrigger::new(item_fn, attributes)?;
        let trigger_tokens = trigger_item.to_token_stream();

        Ok(trigger_tokens.into())
    }

    wrapped(attrs, input).unwrap_or_else(|e| e.into_compile_error().into())
}