substrate/utils: enable wasm builder diagnostics propagation

Cargo.toml

@@ -1200,6 +1200,7 @@ sha1 = { version = "0.10.6" }
 sha2 = { version = "0.10.7", default-features = false }
 sha3 = { version = "0.10.0", default-features = false }
 shell-runtime = { path = "cumulus/parachains/runtimes/starters/shell" }
+shlex = { version = "1.3.0" }
 slot-range-helper = { path = "polkadot/runtime/common/slot_range_helper", default-features = false }
 slotmap = { version = "1.0" }
 smallvec = { version = "1.11.0", default-features = false }

prdoc/pr_5838.prdoc

@@ -0,0 +1,20 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: enable wasm builder diagnostics propagation
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      `substrate-wasm-builder` is used as a build dependency by crates that implement FRAME runtimes.
+      Errors that occur in these crates can not be detected by IDEs that use rust-analyzer as a language
+      server because rust-analyzer needs the errors to be reported as diagnostic message in json format to
+      be able to publish them to language server clients. This PR adds `WASM_BUILD_CARGO_ARGS` environment
+      variable, which can hold a space separated list of args that will be parsed and passed to the `cargo`
+      command that it is used for building against wasm target. It can be used for the stated initial case,
+      but it is also flexible enough to allow passing other arguments or formatting the messages using another
+      available type.
+crates:
+  - name: substrate-wasm-builder 
+    bump: patch
+

substrate/utils/wasm-builder/Cargo.toml

@@ -39,6 +39,7 @@ frame-metadata = { features = ["current"], optional = true, workspace = true, de
 codec = { optional = true, workspace = true, default-features = true }
 array-bytes = { optional = true, workspace = true, default-features = true }
 sp-tracing = { optional = true, workspace = true, default-features = true }
+shlex = { workspace = true }
 
 [features]
 # Enable support for generating the metadata hash.

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

@@ -84,6 +84,9 @@
 //! - `WASM_BUILD_STD` - Sets whether the Rust's standard library crates will also be built. This is
 //!   necessary to make sure the standard library crates only use the exact WASM feature set that
 //!   our executor supports. Enabled by default.
+//! - `WASM_BUILD_CARGO_ARGS` - This can take a string as space separated list of `cargo` arguments.
+//!   It was added specifically for the use case of enabling JSON diagnostic messages during the
+//!   build phase, to be used by IDEs that parse them, but it might be useful for other cases too.
 //! - `CARGO_NET_OFFLINE` - If `true`, `--offline` will be passed to all processes launched to
 //!   prevent network access. Useful in offline environments.
 //!
@@ -161,6 +164,10 @@ const WASM_BUILD_WORKSPACE_HINT: &str = "WASM_BUILD_WORKSPACE_HINT";
 /// Environment variable to set whether we'll build `core`/`std`.
 const WASM_BUILD_STD: &str = "WASM_BUILD_STD";
 
+/// Environment variable to set additional cargo arguments that might be useful
+/// during the build phase.
+const WASM_BUILD_CARGO_ARGS: &str = "WASM_BUILD_CARGO_ARGS";
+
 /// The target to use for the runtime. Valid values are `wasm` (default) or `riscv`.
 const RUNTIME_TARGET: &str = "SUBSTRATE_RUNTIME_TARGET";
 

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

@@ -869,6 +869,18 @@ fn build_bloaty_blob(
 		// We don't want to call ourselves recursively
 		.env(crate::SKIP_BUILD_ENV, "");
 
+	let cargo_args = env::var(crate::WASM_BUILD_CARGO_ARGS).unwrap_or_default();
+	if !cargo_args.is_empty() {
+		let Some(args) = shlex::split(&cargo_args) else {
+			build_helper::warning(format!(
+				"the {} environment variable is not a valid shell string",
+				crate::WASM_BUILD_CARGO_ARGS
+			));
+			std::process::exit(1);
+		};
+		build_cmd.args(args);
+	}
+
 	#[cfg(feature = "metadata-hash")]
 	if let Some(hash) = metadata_hash {
 		build_cmd.env("RUNTIME_METADATA_HASH", array_bytes::bytes2hex("0x", &hash));
@@ -1140,6 +1152,7 @@ fn generate_rerun_if_changed_instructions(
 	println!("cargo:rerun-if-env-changed={}", crate::WASM_BUILD_TOOLCHAIN);
 	println!("cargo:rerun-if-env-changed={}", crate::WASM_BUILD_STD);
 	println!("cargo:rerun-if-env-changed={}", crate::RUNTIME_TARGET);
+	println!("cargo:rerun-if-env-changed={}", crate::WASM_BUILD_CARGO_ARGS);
 }
 
 /// Track files and paths related to the given package to rerun `build.rs` on any relevant change.