feat: Add #[derive(FromRequest)] macro

Minimize the amount of boilerplate that users have to write
in order to extract information out of the incoming request.

Author: LukeMathWalker

runtime/pavex/src/lib.rs

@@ -45,6 +45,8 @@ pub mod time {
 }
 pub mod tls;
 
+pub use pavex_macros::FromRequest;
+
 /// Define a [prebuilt type](https://pavex.dev/docs/guide/dependency_injection/prebuilt_types/).
 ///
 /// Prebuilt types are constructed outside of Pavex's dependency injection framework

runtime/pavex/src/request/error.rs

@@ -0,0 +1,7 @@
+pub struct FromRequestError(crate::Error);
+
+impl FromRequestError {
+    pub fn new(e: crate::Error) -> Self {
+        Self(e)
+    }
+}

runtime/pavex/src/request/mod.rs

@@ -4,9 +4,11 @@
 //!
 //! Check out [the guide](https://pavex.dev/docs/guide/request_data/)
 //! for a thorough introduction to request-based data extractors.
+pub use error::FromRequestError;
 pub use request_head::RequestHead;
 
 pub mod body;
+mod error;
 pub mod path;
 pub mod query;
 mod request_head;

runtime/pavex/src/request/path/path_params.rs

@@ -52,7 +52,7 @@ impl<T> PathParams<T> {
     /// If the extraction fails, an [`ExtractPathParamsError`] is returned.
     #[request_scoped(pavex = crate, id = "PATH_PARAMS_EXTRACT")]
     pub fn extract<'server, 'request>(
-        params: RawPathParams<'server, 'request>,
+        params: &'request RawPathParams<'server, 'request>,
     ) -> Result<Self, ExtractPathParamsError>
     where
         T: Deserialize<'request>,

runtime/pavex/src/request/path/raw_path_params.rs

@@ -77,6 +77,12 @@ impl<'server, 'request> Iterator for RawPathParamsIter<'_, 'server, 'request> {
     }
 }
 
+impl<'server, 'request> ExactSizeIterator for RawPathParamsIter<'_, 'server, 'request> {
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
 /// A wrapper around a percent-encoded path parameter, obtained via [`RawPathParams`].
 ///
 /// Use [`decode`](Self::decode) to extract the percent-encoded value.

runtime/pavex_macros/CONTRIBUTING.md

@@ -0,0 +1,34 @@
+# Testing
+
+`pavex_macros` relies on [`trybuild`](https://github.com/dtolnay/trybuild) to verify that Pavex macros:
+
+- Accept the expected input/parameter combinations
+- Reject invalid input/parameter combinations
+
+In the latter case, we also verify the returned error message to ensure that
+diagnostics are accurate and actionable.
+
+## Test filtering
+
+`trybuild` is a custom test runner and it doesn't obey all `cargo test` built-in options.
+
+For filtering, in particular, use
+
+```bash
+cargo t -- ui trybuild=not_a_function.rs
+```
+
+to run a subset of the whole UI test suite.
+The `trybuild` argument doesn't have to be the filename: you can only specify a fragment of the path (e.g. `from_request`) to run
+all tests in a specific sub-directory.
+
+## Overwriting saved snapshots
+
+To overwrite saved snapshots, set the `TRYBUILD=overwrite` environment variable:
+
+```bash
+# Overwrite all saved snapshots, if changed
+TRYBUILD=overwrite cargo t 
+# Overwrite snapshots for a subset of tests
+TRYBUILD=overwrite cargo t -- ui trybuild=from_request
+```