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//! Tools to stub the implementation or return value of your mocks.
mod once;
use crate::{
matcher::InvocationMatcher,
mock::{Mock, MockTimes, Stub},
mock_store::MockStore,
};
pub use once::Once;
#[doc(hidden)]
pub struct Any;
impl<Arg> InvocationMatcher<Arg> for Any {
/// Always returns Ok(())
fn matches(&self, _: &Arg) -> Result<(), String> {
Ok(())
}
}
/// Provides methods to stub the implementation or return value of the
/// mocked method.
///
/// Created using [`when!`].
///
/// By default, methods are mocked for all invocations. Use [`when!`]
/// for an ergonomic way to set argument matchers. For more features,
/// use [`with_args`].
///
/// By default, all methods are mocked indefinitely. Thus, any stubbed
/// values needs to be cloneable and any stubbed implementation cannot
/// consume variables. Use the [`times`] and [`once`] methods to
/// override these defaults.
///
/// Do *NOT* rely on the signature of `When`. While changing the
/// methods of `When` will be considered a breaking change, changing
/// the generics within `When` will not.
///
/// [`when!`]: crate::when!
/// [`once`]: When::once
/// [`times`]: When::times
/// [`with_args`]: When::with_args
pub struct When<'q, R, I, O, M: InvocationMatcher<I>> {
id: fn(R, I) -> O,
store: &'q mut MockStore,
times: MockTimes,
matcher: M,
}
impl<'q, R, I, O> When<'q, R, I, O, Any> {
#[doc(hidden)]
pub fn new(id: fn(R, I) -> O, store: &'q mut MockStore) -> Self {
When {
id,
store,
matcher: Any,
times: MockTimes::Always,
}
}
}
impl<'q, R, I, O, M: InvocationMatcher<I> + Send + 'static> When<'q, R, I, O, M> {
/// Sets the return value of the mocked method.
///
/// Requires the value to be static. For a more lax but unsafe
/// alternative, use [`then_unchecked_return`].
///
/// The returned value will be cloned on each invocation of the
/// mock. Using this method to return another mock instance will
/// fail unless that mock instance has its clone method already
/// mocked.
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn multi_args(&mut self, a: &i32, b: i8) -> u32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// faux::when!(mock.multi_args).then_return(5);
/// // mock activates multiple times
/// assert_eq!(mock.multi_args(&2, 3), 5);
/// assert_eq!(mock.multi_args(&2, 3), 5);
/// }
/// ```
///
/// [`then_unchecked_return`]: When::then_unchecked_return
pub fn then_return(self, value: O)
where
O: Send + Clone + 'static,
{
self.then(move |_: I| value.clone());
}
/// Sets the implementation of the mocked method to the provided
/// closure.
///
/// The input to the closure is a tuple of all its non-receiver
/// parameters.
///
/// The provided closure can only capture static variables and it
/// must be mocking a method with static output. For a more lax
/// but unsafe alternative, use [`then_unchecked`].
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn no_args(&mut self) -> i32 {
/// /* implementation code */
/// # panic!()
/// }
///
/// pub fn single_arg(&self, a: u8) -> Vec<i8> {
/// /* implementation code */
/// # panic!()
/// }
///
/// pub fn multi_args(self, a: &i32, b: i8) -> u32 {
/// /* implementation code */
/// # panic!()
/// }
///
/// pub fn out_ref(&self) -> &u32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// // method with no params
/// faux::when!(mock.no_args).then(|_| 5);
/// assert_eq!(mock.no_args(), 5);
///
/// // method with a single param
/// faux::when!(mock.single_arg).then(|input| vec![input as i8]);
/// assert_eq!(mock.single_arg(8), vec![8]);
///
/// // method with multiple params - some can be references
/// faux::when!(mock.multi_args).then(|(&a, _)| a as u32);
/// assert_eq!(mock.multi_args(&5, 2), 5);
///
/// // cannot mock methods that return references
/// // let x = 5;
/// // faux::when!(mock.out_ref).then(|_| &x);
/// }
/// ```
///
/// [`then_unchecked`]: When::then_unchecked
pub fn then(self, mock: impl FnMut(I) -> O + 'static + Send)
where
O: 'static,
{
self.store.mock(
self.id,
Mock::new(
Stub::Many {
times: self.times,
stub: Box::new(mock),
},
self.matcher,
),
);
}
/// Analog of [`then_return`] that allows stubbing non-static
/// return values.
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn multi_args(&mut self, a: &i32, b: i8) -> &u32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// let x = 5;
/// unsafe { faux::when!(mock.multi_args).then_unchecked_return(&x) }
/// assert_eq!(*mock.multi_args(&2, 3), x);
/// }
/// ```
///
/// # Safety
///
/// The lifetime of the returned object is not checked and can
/// cause memory safety issues if used incorrectly.
///
/// If the owner of the borrowed data is dropped while the
/// captured reference is still accessible, a use-after-free
/// violation will be triggered.
///
/// This method can also cause aliasing issues where multiple
/// mutable references are held for the same object.
///
/// ### Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn out_ref(&self) -> &u32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// let x = 5;
/// unsafe { faux::when!(mock.out_ref).then_unchecked_return(&x) }
/// std::mem::drop(x);
/// // assert_eq!(*mock.ref_return(), 5); // <~~ UB: use after free
/// }
/// ```
///
/// [`then_return`]: When::then_return
pub unsafe fn then_unchecked_return(self, value: O)
where
O: Send + Clone,
{
self.then_unchecked(move |_: I| value.clone())
}
/// Analog of [`then`] that allows stubbing implementations with
/// non-static closures.
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn out_ref(&mut self) -> &i32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// // the output can be a reference to the environment
/// // but this can be *very* dangerous
/// let x = 5;
/// unsafe { faux::when!(mock.out_ref).then_unchecked(|_| &x) }
/// assert_eq!(*mock.out_ref(), x);
/// }
///
/// ```
///
///
/// # Safety
///
/// The lifetimes of the outputs and captured variables are not
/// checked. While this gives the caller maximum flexibility when
/// mocking, it is *not* memory safe when used incorrectly.
///
/// If the mocked method is called after its captured variables
/// are dropped then a use-after-free violation will be triggered.
///
/// Relationships between inputs, outputs, and captured variable
/// lifetimes are lost. This allows for easy violations of Rust's
/// aliasing checks, creating undefined behavior.
///
/// ### Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn out_ref(&self, a : &mut i32) -> &mut i32 {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
/// // the output and input references are the same
/// unsafe { faux::when!(mock.out_ref).then_unchecked(|i| i) }
///
/// let mut x = 5;
/// // y (the output) is a mutable reference back to x (the input)
/// // but there is no compile-time link between the two
/// let y = mock.out_ref(&mut x);
///
/// // x and y are pointing to the same data!
/// assert_eq!(*y, 5);
/// assert_eq!(x, 5);
///
/// // changes in x are reflected in y and vice versa
/// // this is UB and is not allowed in safe Rust!
/// x += 1;
/// assert_eq!(x, 6);
/// assert_eq!(*y, 6);
/// }
/// ```
///
/// [`then`]: When::then
pub unsafe fn then_unchecked(self, mock: impl FnMut(I) -> O + Send) {
self.store.mock_unchecked(
self.id,
Mock::new(
Stub::Many {
times: self.times,
stub: Box::new(mock),
},
self.matcher,
),
);
}
/// Limits the number of calls for which a mock is active.
///
/// Calls past the limit will result in a panic.
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn single_arg(&self, a: u8) -> Vec<i8> {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// // limit to 5 calls
/// faux::when!(mock.single_arg)
/// .times(5)
/// .then(|input| vec![input as i8]);
///
/// // can be called 5 times
/// for _ in 0..5 {
/// assert_eq!(mock.single_arg(8), vec![8]);
/// }
/// }
/// ```
///
/// ## Panics
///
/// Panics if the mock is called more times than specified.
///
/// ```rust should_panic
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn single_arg(&self, a: u8) -> Vec<i8> {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// // limit to 5 calls
/// faux::when!(mock.single_arg)
/// .times(5)
/// .then(|input| vec![input as i8]);
///
/// // panics on the 6th call
/// for _ in 0..6 {
/// assert_eq!(mock.single_arg(8), vec![8]);
/// }
/// }
/// ```
pub fn times(mut self, times: usize) -> Self {
self.times = MockTimes::Times(times);
self
}
/// Limits mock to one call, allowing mocks to consume captured variables.
///
/// Panics if the mock is called more than once.
///
/// # Examples
///
/// ```rust
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn single_arg(&self, a: u8) -> Vec<i8> {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// let vec = vec![25];
/// // moves vec to the closure
/// faux::when!(mock.single_arg).once().then(|_| vec);
/// assert_eq!(mock.single_arg(8), vec![25]);
/// }
/// ```
///
/// # Panics
///
/// Panics if the mock is called more than once.
///
/// ```rust should_panic
/// #[faux::create]
/// pub struct Foo {}
///
/// #[faux::methods]
/// impl Foo {
/// pub fn single_arg(&self, a: u8) -> Vec<i8> {
/// /* implementation code */
/// # panic!()
/// }
/// }
///
/// fn main() {
/// let mut mock = Foo::faux();
///
/// let vec = vec![25];
/// faux::when!(mock.single_arg).once().then(|_| vec);
/// assert_eq!(mock.single_arg(8), vec![25]);
/// //panics on its second call
/// mock.single_arg(8);
/// }
/// ```
pub fn once(self) -> Once<'q, R, I, O, M> {
Once::new(self.id, self.store, self.matcher)
}
/// Specifies a matcher for the invocation.
///
/// This lets you pass matchers for each method argument.
///
/// See [`when!`](crate::when!) for an ergonomic way to pass the
/// matcher.
///
/// If all arguments implement [`Debug`](std::fmt::Debug), a tuple
/// of [`ArgMatcher`](crate::ArgMatcher)s can be provided where
/// each `ArgMatcher` matches an individual argument.
///
/// If the method only has a single argument, use a tuple of a
/// single element: `(ArgMatcher,)`
///
/// For more complex cases, you may pass a custom
/// [`InvocationMatcher`](InvocationMatcher).
pub fn with_args<N: InvocationMatcher<I> + Send + 'static>(
self,
matcher: N,
) -> When<'q, R, I, O, N> {
When {
matcher,
times: self.times,
id: self.id,
store: self.store,
}
}
}