feat(react-compiler): advance SWC parity for upstream fixtures#11724
feat(react-compiler): advance SWC parity for upstream fixtures#11724
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Commit: 1ab9f8a |
PR Review: feat(react-compiler): advance SWC parity for upstream fixturesOverall this is solid parity work advancing the React Compiler implementation. The refactoring of dependency collection into composable, reusable functions is a clear improvement. A few observations: Code QualityPositive:
Suggestions:
Performance Considerations
Potential Issues
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Minor
Overall this is well-structured progress toward upstream parity. The main actionable items are the unused |
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Pull request overview
This PR advances swc_ecma_react_compiler parity with upstream React Compiler fixtures by tightening fixture pragma parsing, expanding environment configuration, strengthening useMemo validation, and improving reactive dependency inference (notably around optional chaining/member access and capture splitting).
Changes:
- Expanded fixture pragma parsing + Flow fixture normalization to better match upstream semantics.
- Implemented/extended
validate_use_memochecks and wired them through compilation options. - Enhanced
reactive_scopesdependency collection/reduction (optional/member access handling, prelude/capture splitting) and added an anonymous-function naming transform.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
crates/swc_ecma_react_compiler/tests/fixture.rs |
Adds Flow fixture normalizations, refactors parsing, expands pragma support, and changes fixture suite execution modes. |
crates/swc_ecma_react_compiler/src/validation/validate_use_memo.rs |
Implements useMemo callback validation (params/async/generator/purity/void checks) with env-controlled behavior. |
crates/swc_ecma_react_compiler/src/transform/mod.rs |
Implements a pass to assign stable names to anonymous function expressions based on local bindings. |
crates/swc_ecma_react_compiler/src/reactive_scopes/mod.rs |
Improves dependency inference/reduction and normalization passes (incl. optional/member access and prelude splitting adjustments). |
crates/swc_ecma_react_compiler/src/options.rs |
Extends EnvironmentConfig and introduces InstrumentationOptions to support new flags/options. |
crates/swc_ecma_react_compiler/src/lib.rs |
Re-exports InstrumentationOptions as part of the public API surface. |
crates/swc_ecma_react_compiler/src/entrypoint/program.rs |
Wires new validate_use_memo signature and the anonymous-function naming transform into the pipeline. |
.github/workflows/CI.yml |
Alters CI to run swc_ecma_react_compiler tests with fixture failures allowed. |
Comments suppressed due to low confidence (1)
crates/swc_ecma_react_compiler/tests/fixture.rs:1601
- The upstream fixture tests (
fixture_cases_upstream*) are no longer gated/ignored and will run in a defaultcargo test -p swc_ecma_react_compilerinvocation. Given the current upstream parity status (many known mismatches), this makes the crate's default test run fail for most contributors. Consider restoring an opt-in gate (env var) or marking these tests#[ignore]by default so local development isn't blocked while parity work is in progress.
#[test]
fn fixture_cases_upstream() {
let fixture_root = fixtures_root();
let manifest = configured_path(
&fixture_root,
"REACT_COMPILER_UPSTREAM_MANIFEST",
"upstream_manifest.txt",
);
let upstream_root = configured_path(&fixture_root, "REACT_COMPILER_UPSTREAM_ROOT", "upstream");
let inputs = upstream_inputs(&manifest, &upstream_root);
assert!(
!inputs.is_empty(),
"no upstream fixtures found. run `scripts/sync_fixtures.sh --manifest \
tests/fixtures/upstream_manifest.txt --out-dir tests/fixtures/upstream` first"
);
run_fixture_suite(inputs);
}
#[test]
fn fixture_cases_upstream_phase1() {
let fixture_root = fixtures_root();
let manifest = configured_path(
&fixture_root,
"REACT_COMPILER_UPSTREAM_PHASE1_MANIFEST",
"upstream_phase1_manifest.txt",
);
// Phase1 fixtures live in the same upstream root, selected by manifest.
let upstream_root = configured_path(
&fixture_root,
"REACT_COMPILER_UPSTREAM_PHASE1_ROOT",
"upstream",
);
let inputs = upstream_inputs(&manifest, &upstream_root);
assert!(
!inputs.is_empty(),
"no upstream phase1 fixtures found. run `scripts/sync_fixtures.sh --manifest \
tests/fixtures/upstream_phase1_manifest.txt --out-dir tests/fixtures/upstream` first"
);
run_fixture_suite(inputs);
}
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| - name: Run cargo test | ||
| if: matrix.settings.crate != '__noop__' && matrix.settings.crate != 'swc_plugin_backend_tests' && matrix.settings.crate != 'swc_ecma_parser' && matrix.settings.crate != 'swc_ecma_minifier' && matrix.settings.crate != 'swc_core' && matrix.settings.crate != 'swc_ecma_quote' && matrix.settings.crate != 'swc_cli' && matrix.settings.crate != 'binding_core_wasm' && matrix.settings.crate != 'hstr' | ||
| if: matrix.settings.crate != '__noop__' && matrix.settings.crate != 'swc_plugin_backend_tests' && matrix.settings.crate != 'swc_ecma_parser' && matrix.settings.crate != 'swc_ecma_minifier' && matrix.settings.crate != 'swc_core' && matrix.settings.crate != 'swc_ecma_quote' && matrix.settings.crate != 'swc_cli' && matrix.settings.crate != 'binding_core_wasm' && matrix.settings.crate != 'hstr' && matrix.settings.crate != 'swc_ecma_react_compiler' | ||
| run: | | ||
| cargo test -p ${{ matrix.settings.crate }} | ||
|
|
||
| - name: Run cargo test (swc_ecma_react_compiler) | ||
| if: matrix.settings.crate == 'swc_ecma_react_compiler' | ||
| env: | ||
| REACT_COMPILER_FIXTURE_ALLOW_FAILURE: 1 | ||
| run: | | ||
| cargo test -p swc_ecma_react_compiler | ||
|
|
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The CI job sets REACT_COMPILER_FIXTURE_ALLOW_FAILURE=1 for the entire swc_ecma_react_compiler test run, which makes fixture test failures non-fatal and can hide regressions (including local fixture failures). Consider restricting this env var to upstream fixture tests only (e.g. run a separate cargo test that targets upstream-only tests with the env var, and keep the default cargo test -p swc_ecma_react_compiler step strict).
| fn collect_function_like_bindings(body: &BlockStmt) -> HashMap<String, FunctionLike> { | ||
| let mut out = HashMap::new(); | ||
| for stmt in &body.stmts { | ||
| if let Stmt::Decl(swc_ecma_ast::Decl::Var(var_decl)) = stmt { | ||
| for decl in &var_decl.decls { | ||
| let Pat::Ident(binding) = &decl.name else { | ||
| continue; | ||
| }; | ||
| let Some(init) = &decl.init else { | ||
| continue; | ||
| }; | ||
| match &**init { | ||
| Expr::Fn(fn_expr) => { | ||
| out.insert( | ||
| binding.id.sym.to_string(), | ||
| FunctionLike::Function(*fn_expr.function.clone()), | ||
| ); | ||
| } | ||
| Expr::Arrow(arrow) => { | ||
| out.insert( | ||
| binding.id.sym.to_string(), | ||
| FunctionLike::Arrow(arrow.clone()), | ||
| ); | ||
| } | ||
| _ => {} | ||
| } | ||
| } | ||
| } | ||
| } | ||
| out | ||
| } |
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collect_function_like_bindings only collects const foo = () => {} / const foo = function() {} from top-level var declarations. As a result, useMemo(foo) where foo is a function foo() {} declaration (or other binding forms) will skip all callback validations (params/async/generator/outer reassignment/no-void), creating inconsistent behavior depending on how the callback is written. Consider extending the binding collection to include Stmt::Decl(Decl::Fn(..)) (and any other forms you intend to support) so identifier callbacks are validated consistently.
| fn assigns_outer_context(function_like: &FunctionLike, parent_bindings: &HashSet<String>) -> bool { | ||
| let mut local_bindings = HashSet::new(); | ||
| match function_like { | ||
| FunctionLike::Function(function) => { | ||
| for param in &function.params { | ||
| collect_pat_bindings(¶m.pat, &mut local_bindings); | ||
| } | ||
| if let Some(body) = &function.body { | ||
| for stmt in &body.stmts { | ||
| collect_stmt_bindings(stmt, &mut local_bindings); | ||
| } | ||
| } | ||
| } | ||
| FunctionLike::Arrow(arrow) => { | ||
| for param in &arrow.params { | ||
| collect_pat_bindings(param, &mut local_bindings); | ||
| } | ||
| if let swc_ecma_ast::BlockStmtOrExpr::BlockStmt(body) = &*arrow.body { | ||
| for stmt in &body.stmts { | ||
| collect_stmt_bindings(stmt, &mut local_bindings); | ||
| } | ||
| } |
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assigns_outer_context builds local_bindings by collecting params and only the callback body's top-level statements. This misses bindings declared inside nested blocks (e.g. if (...) { let a = ... }), which can cause false positives when a nested binding shadows an outer name and is then assigned (a = ...). Consider collecting bindings recursively through nested blocks/loops/try blocks (similar to the existing collect_stmt_bindings_including_nested_blocks helper used elsewhere) so shadowed locals are recognized.
| if allow_fixture_failures_mode() { | ||
| eprintln!( | ||
| "fixture suite failed (allowed): {}/{} failed\n{}", | ||
| failed.len(), | ||
| total, | ||
| failed_summary | ||
| ); | ||
| return; | ||
| } |
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REACT_COMPILER_FIXTURE_ALLOW_FAILURE currently suppresses failures for all fixture suites (including fixture_cases_local). This can mask regressions in local fixtures when the env var is set (e.g. in CI). Consider scoping the "allowed failure" behavior to upstream fixture suites only (by passing a flag into run_fixture_suite, or by checking the fixture root/path), while keeping local fixtures hard-failing.
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| FunctionLike::Arrow(arrow) => { | ||
| arrow.visit_with(&mut finder); |
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Traverse arrow callback body when checking outer writes
assigns_outer_context builds an AssignFinder that skips visit_arrow_expr, but then runs it on the callback via arrow.visit_with(&mut finder). That means the root arrow callback body is never traversed, so mutations like useMemo(() => { outer = 1; }, []) are silently accepted even though this validator is supposed to reject reassigning outer bindings.
Useful? React with 👍 / 👎.
| for stmt in &body.stmts { | ||
| if let Stmt::Decl(swc_ecma_ast::Decl::Var(var_decl)) = stmt { | ||
| for decl in &var_decl.decls { |
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Resolve function declarations for
useMemo callback identifiers
collect_function_like_bindings only records function-like values from var declarations, so callbacks passed by identifier from function declarations are not resolved. In cases like function compute(x) {}; useMemo(compute, []), resolve_callback_like returns None and all callback validations are skipped, creating false negatives for parameter, async/generator, purity, and return-value checks.
Useful? React with 👍 / 👎.
Summary
EnvironmentConfigand align option/default application paths used by plugin options and fixture pragmas.ValidateUseMemobehavior and related transform wiring.reactive_scopes(including optional/member access handling and prelude/capture dependency splitting).Scope
crates/swc_ecma_react_compilerTest status
cargo fmt --allcargo clippy -p swc_ecma_react_compiler --all-targets -- -D warningscargo test -p swc_ecma_react_compiler fixture_cases_local -- --nocapturecargo test -p swc_ecma_react_compiler fixture_cases_upstream_phase1 -- --nocaptureREACT_COMPILER_FIXTURE_CONTINUE_ON_FAIL=1 cargo test -p swc_ecma_react_compiler fixture_cases_upstream -- --nocaptureCurrent upstream fixture progress from the latest run:
1070/1718fixture mismatch=844,missing_diagnostic=192,missing_error_fragment=340Notes