fix: make building of kernel errors file conditional on env variable

.github/workflows/lint.yml

@@ -71,3 +71,18 @@ jobs:
           override: true
       - name: check rust versions
         run: ./scripts/check-rust-version.sh
+
+  kernel_errors:
+    name: kernel errors check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@main
+      - name: Rustup
+        run: rustup update --no-self-update
+      - uses: Swatinem/rust-cache@v2
+        with:
+          save-if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/next' }}
+      - name: Rebuild kernel errors
+        run: BUILD_KERNEL_ERRORS=1 cargo check -p miden-tx
+      - name: Diff check
+        run: git diff --exit-code

Makefile

@@ -9,6 +9,7 @@ help:
 WARNINGS=RUSTDOCFLAGS="-D warnings"
 DEBUG_ASSERTIONS=RUSTFLAGS="-C debug-assertions"
 ALL_FEATURES_BUT_ASYNC=--features concurrent,testing
+BUILD_KERNEL_ERRORS=BUILD_KERNEL_ERRORS=1
 
 # -- linting --------------------------------------------------------------------------------------
 
@@ -70,18 +71,18 @@ test: test-default test-prove ## Run all tests
 
 .PHONY: check
 check: ## Check all targets and features for errors without code generation
-	cargo check --all-targets $(ALL_FEATURES_BUT_ASYNC)
+	${BUILD_KERNEL_ERRORS} cargo check --all-targets $(ALL_FEATURES_BUT_ASYNC)
 
 # --- building ------------------------------------------------------------------------------------
 
 .PHONY: build
 build: ## By default we should build in release mode
-	cargo build --release
+	${BUILD_KERNEL_ERRORS} cargo build --release
 
 
 .PHONY: build-no-std
 build-no-std: ## Build without the standard library
-	cargo build --no-default-features --target wasm32-unknown-unknown --workspace --lib
+	${BUILD_KERNEL_ERRORS} cargo build --no-default-features --target wasm32-unknown-unknown --workspace --lib
 
 
 .PHONY: build-no-std-testing
@@ -91,7 +92,7 @@ build-no-std-testing: ## Build without the standard library. Includes the `testi
 
 .PHONY: build-async
 build-async: ## Build with the `async` feature enabled (only libraries)
-	cargo build --lib --release --features async
+	${BUILD_KERNEL_ERRORS} cargo build --lib --release --features async
 
 
 # --- benchmarking --------------------------------------------------------------------------------

miden-tx/build.rs

@@ -11,10 +11,20 @@ const ASM_DIR: &str = "../miden-lib/asm";
 const KERNEL_ERRORS_FILE: &str = "src/errors/tx_kernel_errors.rs";
 const MASM_FILE_EXTENSION: &str = "masm";
 
+/// Generates error mappings for transaction kernel errors.
+///
+/// This is done only if BUILD_KERNEL_ERRORS environment variable is set to `1` to avoid running
+/// the script on crates.io where MASM files from miden-lib are not available.
 fn main() -> Result<()> {
     // re-build when the MASM code changes
     println!("cargo:rerun-if-changed={ASM_DIR}");
     println!("cargo:rerun-if-changed={KERNEL_ERRORS_FILE}");
+    println!("cargo::rerun-if-env-changed=BUILD_KERNEL_ERRORS");
+
+    // Skip this build script in BUILD_KERNEL_ERRORS environment variable is not set to `1`.
+    if env::var("BUILD_KERNEL_ERRORS").unwrap_or("0".to_string()) == "0" {
+        return Ok(());
+    }
 
     // Copies the MASM code to the build directory
     let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();