Wasm-builder runtime-wasm feature (#6177)

* Enable the `runtime-wasm` for wasm builds

This enables the `runtime-wasm` feature for wasm builds. The feature is
not mandatory and will only be activated if it exists in the
`Cargo.toml`.

* Fix compilation

* Update docs

* Uprgade version

* Apply suggestions from code review

substrate/utils/wasm-builder/src/lib.rs

@@ -15,14 +15,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//! # WASM builder is a utility for building a project as a WASM binary
+//! # Wasm builder is a utility for building a project as a Wasm binary
 //!
-//! The WASM builder is a tool that integrates the process of building the WASM binary of your project into the main
+//! The Wasm builder is a tool that integrates the process of building the WASM binary of your project into the main
 //! `cargo` build process.
 //!
 //! ## Project setup
 //!
-//! A project that should be compiled as a WASM binary needs to:
+//! A project that should be compiled as a Wasm binary needs to:
 //!
 //! 1. Add a `build.rs` file.
 //! 2. Add `substrate-wasm-builder` as dependency into `build-dependencies`.
@@ -48,12 +48,20 @@
 //! include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 //! ```
 //!
-//! This will include the generated WASM binary as two constants `WASM_BINARY` and `WASM_BINARY_BLOATY`.
-//! The former is a compact WASM binary and the latter is not compacted.
+//! This will include the generated Wasm binary as two constants `WASM_BINARY` and `WASM_BINARY_BLOATY`.
+//! The former is a compact Wasm binary and the latter is not compacted.
+//!
+//! ### Feature
+//!
+//! Wasm builder supports to enable cargo features while building the Wasm binary. By default it will
+//! enable all features in the wasm build that are enabled for the native build except the
+//! `default` and `std` features. Besides that, wasm builder supports the special `runtime-wasm`
+//! feature. This `runtime-wasm` feature will be enabled by the wasm builder when it compiles the
+//! Wasm binary. If this feature is not present, it will not be enabled.
 //!
 //! ## Environment variables
 //!
-//! By using environment variables, you can configure which WASM binaries are built and how:
+//! By using environment variables, you can configure which Wasm binaries are built and how:
 //!
 //! - `SKIP_WASM_BUILD` - Skips building any wasm binary. This is useful when only native should be recompiled.
 //! - `BUILD_DUMMY_WASM_BINARY` - Builds dummy wasm binaries. These dummy binaries are empty and useful
@@ -61,7 +69,7 @@
 //! - `WASM_BUILD_TYPE` - Sets the build type for building wasm binaries. Supported values are `release` or `debug`.
 //!                       By default the build type is equal to the build type used by the main build.
 //! - `TRIGGER_WASM_BUILD` - Can be set to trigger a wasm build. On subsequent calls the value of the variable
-//!                          needs to change. As WASM builder instructs `cargo` to watch for file changes
+//!                          needs to change. As wasm builder instructs `cargo` to watch for file changes
 //!                          this environment variable should only be required in certain circumstances.
 //! - `WASM_BUILD_RUSTFLAGS` - Extend `RUSTFLAGS` given to `cargo build` while building the wasm binary.
 //! - `WASM_BUILD_NO_COLOR` - Disable color output of the wasm build.
@@ -76,7 +84,7 @@
 //!
 //! ## Prerequisites:
 //!
-//! WASM builder requires the following prerequisites for building the WASM binary:
+//! Wasm builder requires the following prerequisites for building the Wasm binary:
 //!
 //! - rust nightly + `wasm32-unknown-unknown` toolchain
 //!

substrate/utils/wasm-builder/src/wasm_project.rs

@@ -308,15 +308,25 @@ fn create_wasm_workspace_project(wasm_workspace: &Path, workspace_root_path: &Pa
 	);
 }
 
+/// Find a package by the given `manifest_path` in the metadata.
+///
+/// Panics if the package could not be found.
+fn find_package_by_manifest_path<'a>(
+	manifest_path: &Path,
+	crate_metadata: &'a cargo_metadata::Metadata,
+) -> &'a cargo_metadata::Package {
+	crate_metadata.packages
+		.iter()
+		.find(|p| p.manifest_path == manifest_path)
+		.expect("Wasm project exists in its own metadata; qed")
+}
+
 /// Get a list of enabled features for the project.
 fn project_enabled_features(
 	cargo_manifest: &Path,
 	crate_metadata: &cargo_metadata::Metadata,
 ) -> Vec<String> {
-	let package = crate_metadata.packages
-		.iter()
-		.find(|p| p.manifest_path == cargo_manifest)
-		.expect("Wasm project exists in its own metadata; qed");
+	let package = find_package_by_manifest_path(cargo_manifest, crate_metadata);
 
 	let mut enabled_features = package.features.keys()
 		.filter(|f| {
@@ -338,6 +348,16 @@ fn project_enabled_features(
 	enabled_features
 }
 
+/// Returns if the project has the `runtime-wasm` feature
+fn has_runtime_wasm_feature_declared(
+	cargo_manifest: &Path,
+	crate_metadata: &cargo_metadata::Metadata,
+) -> bool {
+	let package = find_package_by_manifest_path(cargo_manifest, crate_metadata);
+
+	package.features.keys().any(|k| k == "runtime-wasm")
+}
+
 /// Create the project used to build the wasm binary.
 ///
 /// # Returns
@@ -348,9 +368,14 @@ fn create_project(cargo_manifest: &Path, wasm_workspace: &Path, crate_metadata:
 	let wasm_binary = get_wasm_binary_name(cargo_manifest);
 	let project_folder = wasm_workspace.join(&crate_name);
 
-	fs::create_dir_all(project_folder.join("src")).expect("Wasm project dir create can not fail; qed");
+	fs::create_dir_all(project_folder.join("src"))
+		.expect("Wasm project dir create can not fail; qed");
 
-	let enabled_features = project_enabled_features(&cargo_manifest, &crate_metadata);
+	let mut enabled_features = project_enabled_features(&cargo_manifest, &crate_metadata);
+
+	if has_runtime_wasm_feature_declared(cargo_manifest, crate_metadata) {
+		enabled_features.push("runtime-wasm".into());
+	}
 
 	write_file_if_changed(
 		project_folder.join("Cargo.toml"),