## Root cause
The `oxc_react_compiler` snapshot harness (`tests/snapshot.rs`) rendered a clean no-op compile as the literal `No changes.` marker:
```rust
if result.changed {
out.push_str(&Codegen::new().build(&program).code);
} else {
out.push_str("No changes.");
}
```
Upstream's `snap` runner instead **always** re-emits the program as `## Code`, and only replaces it with `## Error` on a hard error. So for every fixture where oxc "bails" with `No changes.`, the fork's golden shows the reprinted source — a permanent, opaque diff.
Investigating the **rules-of-hooks** batch showed this is purely a harness-representation gap, not a compiler bug:
- All 17 "bailing" rules-of-hooks fixtures carry `@expectNothingCompiled` (e.g. top-level statements, classes, or `@compilationMode:"infer"` functions that aren't components/hooks). oxc correctly compiles nothing — matching the fork, which also compiles nothing and just reprints the source.
- Every rules-of-hooks **error** fixture already matches the fork on category, message text, and source location (Rules-of-Hooks validation is a complete port).
- Every rules-of-hooks **compiling** fixture already matches the fork structurally; residual diffs are pure codegen formatting (trailing commas, JSX paren-wrapping) which are out of scope.
## Fix
Test-only change. On a clean no-op (no parse errors **and** no compile diagnostics), codegen the unchanged program instead of the marker, mirroring the upstream runner. The marker is kept when an error was reported, since upstream emits `## Error` with no code there — and reprinting a parse-recovered AST would be misleading.
```rust
let clean = parsed.diagnostics.is_empty() && result.diagnostics.as_slice().is_empty();
if result.changed || clean {
out.push_str(&Codegen::new().build(&program).code);
} else {
out.push_str("No changes.");
}
```
No compiler source is touched, so there is no risk to the compiler, napi bindings, or other consumers. The snapshot test still catches any future behavior change.
## Fixtures changed
54 snapshots that previously said `No changes.` now render the reprinted source:
- **17 rules-of-hooks** (this batch) — all `@expectNothingCompiled`; now match the fork's `## Code` modulo whitespace.
- **37 elsewhere** (guarded corpus-wide no-ops: `infer-*`, `use-no-forget-*`, `use-no-memo-*`, `gating/*`, `effect-derived-computations/*`, `valid-setState-*`, etc.).
52 of the 54 match the fork's `## Code` modulo formatting. The 11 parse-error fixtures (`error.todo-*`) keep the marker as intended.
## Remaining work
Two of the changed snapshots move **closer** to the fork but retain **pre-existing, out-of-batch** compiler gaps (unchanged by this PR, now just more visible):
- `ignore-use-no-forget.js` — oxc doesn't implement the `@ignoreUseNoForget` plugin option, so it honors the `'use no forget'` opt-out and skips; the fork ignores the opt-out and fully compiles.
- `valid-setState-in-effect-from-ref-function-call.js` — in `@outputMode:"lint"` the fork reprints with an SSA-renamed shadowed param (`ref` → `ref_0`); oxc leaves the source unchanged.
Both are separate from Rules-of-Hooks and left to their respective batches.
## Summary
`oxc_react_compiler` had no committed test over the upstream React
Compiler fixture corpus — the fixtures lived only in the
`oxc-project/forked-react-compiler` checkout, exercised out-of-tree.
That gap let real regressions slip past the 15 in-crate integration
tests. This PR closes it.
- **`crates/oxc_react_compiler/fixtures/`** — 1734 fixture *input* files
(`.js`/`.ts`/`.tsx`/`.jsx`/`.mjs`), copied from the fork's
`babel-plugin-react-compiler/src/__tests__/fixtures/compiler` tree with
subdirectories preserved. Flow fixtures (the `@flow`-pragma ones) are
excluded — oxc has no Flow parser. The upstream `.expect.md` goldens are
also not copied; insta is the golden here.
- **`crates/oxc_react_compiler/tests/snapshot.rs`** — an `insta::glob!`
test that, per fixture, derives `PluginOptions`/`EnvironmentConfig` from
the first-line `// @directive` pragmas (base `compilationMode=all` /
`panicThreshold=all_errors`, matching the upstream `snap` runner),
parses → builds semantic → runs `transform`, and snapshots the compiled
output plus diagnostics. Unrecognised directives are ignored, as
upstream does; camelCase flag directives map to `EnvironmentConfig`
fields via `convert_case`.
- **`crates/oxc_react_compiler/tests/snapshots/`** — 1734 committed
`.snap` goldens (oxc's own output).
- **`.typos.toml`** — excludes the fixtures dir (the upstream fixtures
contain intentional typos; `**/*.snap` was already excluded).
These snapshots are oxc's own golden output, so `cargo test` (and CI)
now catches any change in compiler behaviour across the corpus.
Regenerate after an intended change with `cargo insta accept`.
## Verification
- `cargo test -p oxc_react_compiler` passes — the 1734-fixture snapshot
test plus the existing 15 integration tests; also green under
`--all-features` (matches the cross-target CI job).
- clippy `-D warnings`, `cargo fmt`, and `typos` clean.
- No fixture panics; 1336 compiled / 398 unchanged / 335 with
diagnostics.
- The `error.*` fixtures capture the exact diagnostics — including the
"Cannot reassign variable after render" error that a recent scoping
change had silently suppressed, confirming the suite catches real
regressions.
---
AI usage disclosure: authored with Claude Code and reviewed before
submission.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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