feat(core): broaden .understandignore starter — Rust test/bench patterns#582
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Lum1104 merged 5 commits intoJul 19, 2026
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Rust's official Cargo convention is `benches/` (plural, trailing `s`), matching the target type documented at https://doc.rust-lang.org/cargo/reference/cargo-targets.html — every `.rs` file under that directory compiles as a separate benchmark binary. The existing list picked up the C++-style `bench` / `benchmark` / `benchmarks` variants but missed the Rust one, so Cargo workspaces were silently getting their criterion / test::Bencher sources indexed. Add the plural form as a case-insensitive exact-name match. Also useful to any language that adopts the naming (some Go and Zig projects use `benches/` too).
Rust's dominant unit-test convention is inline `#[cfg(test)] mod tests
{ ... }` blocks that cannot be excluded by filename — anyone wanting to
strip those has to post-process the source. The one file-pattern the
Rust Book (chapter 11.3) does describe is extracting that block into a
sibling `tests.rs` file next to `mod.rs` or `lib.rs`; that extracted
form is what a `**/tests.rs` rule can catch.
Integration tests already live under `tests/` (existing dir rule) and
benchmarks under `benches/` (added in the previous commit), so the
new file-pattern group is deliberately minimal — just the one glob
the community has actually converged on.
Tests: assert the Rust sub-header + pattern emission, and extend the
stable-order invariant to place Rust after Python.
Measurement across 10 large public Rust repos showed the tests.rs-only group carries almost no weight — the majority of file-glob hits come from workspaces that colocate a `foo_test.rs` next to `foo.rs` rather than using extracted `tests.rs` modules. In paritytech/polkadot-sdk this shape accounts for 232 files and a 15% reduction on the analysed budget; in rust-lang/rust it accounts for 253 files (3% reduction on the truncated tree, i.e. a lower bound). Add: **/test_*.rs — pytest / unittest style (less common in Rust) **/*_test.rs — dominant convention in Rust workspace monorepos Kept as separate globs from `**/tests.rs` so users on projects that follow the Rust Book pattern (single sibling tests.rs per module) aren't forced to also strip a naming shape they never use.
Most Rust benchmarks live under `benches/` (already covered by the directory rule added earlier in this branch), so these file-name patterns are mostly a defensive belt-and-braces for the small set of Cargo workspaces that keep bench targets alongside library code rather than under the canonical `benches/` tree. Kept commented-out; contributes negligibly to the token savings for mainstream layouts but preserves symmetry with the C++ group, which already ships `*_benchmark.cc` and `*Benchmark.cpp`.
The initial comment implied `tests.rs` was the load-bearing pattern.
Measurement across 10 major public Rust repos (rust-lang/rust, tokio,
cargo, ripgrep, alacritty, helix, deno, solana, foundry, polkadot-sdk)
showed the actual distribution is bimodal:
- Library-scale crates keep tests inline via `#[cfg(test)] mod`,
which no file-pattern rule can touch → group is a near-noop.
- Workspace monorepos colocate `foo_test.rs` beside `foo.rs` at
scale → `*_test.rs` alone accounts for the vast majority of hits
(232 in polkadot-sdk, 253 in rust-lang/rust even with truncated
tree).
Rewrite the block comment so a future reader lands on the right mental
model — the extracted `tests.rs` form is legitimate but rare; the win
comes from the colocated shape in workspace-heavy repos.
Contributor
Author
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@Lum1104 Please take a look. |
Collaborator
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Great, thanks for the PR! |
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Summary
EXACT_DIR_NAMES+=benches— Cargo's canonical plural benchmark directory (currently only the singular / C++-stylebench/benchmark/benchmarksvariants are recognised).TEST_PATTERN_GROUPSentryRustwith 5 patterns (Rust Booktests.rs, colocated*_test.rs/test_*.rs, criterionbench_*.rs/*_bench.rs).ignore-generator.test.ts; ordering invariant extended to place Rust after Python.scala-extractor.test.ts/swift-extractor.test.tsreproduce unmodified onorigin/main).SKILL.mdunchanged — Phase 0.5 delegates togenerate-ignore.mjssince a0155c5, so no inline duplicate to keep in sync.Why these patterns (and not others)
Rust testing is bimodal:
#[cfg(test)] mod tests { … }— no file-pattern rule can touch them, group is a near-noop.foo_test.rsnext tofoo.rsat scale — dir rules miss them entirely; file patterns are load-bearing.Rejected as too project-specific or ambiguous:
**/*Test.rs(PascalCase Rust filenames are rare — snake_case dominates),**/it_*.rs/**/*_it.rs(no Rust ecosystem uses "IT" as an integration-test marker — integration tests live undertests/),**/*Bench.rs(PascalCase, effectively unused).Kept
**/tests.rsand**/*_test.rsas separate globs so users on Rust Book–style projects (single siblingtests.rsper module) aren't forced to also strip a colocated-file shape they never use.Token impact (measured across ~60 public Rust repos)
Methodology:
gh api .../git/trees?recursive=1, Rust source =.rs, 1 MiB ≈ 262K tokens. Two hero projects reported below — the highest percentage win and the highest absolute win — because Rust's ecosystem produces genuinely bimodal savings.paritytech/parity-commonparitytech/polkadot-sdkparity-common— small utility-crate monorepo, best % result in the survey. Colocated*_test.rsfiles dominate the source tree.polkadot-sdk— largest absolute saving. 232 files match the new file globs; 28 more sit underbenches/subdirs the current rule misses. All reside outside the current directory-ignore surface (substrate/frame/**/*_test.rssits directly next to the pallet source).Unlike C++ (PR #480, up to 62% on nlohmann/json) and Python (PR #579, 47% on tensorflow), Rust never approaches those percentages in the wild because the dominant unit-test convention is inline
#[cfg(test)] mod tests { … }— invisible to any file-pattern rule. That's the ecosystem, not a gap in these patterns. The opt-in model means library-scale projects incur zero behaviour change unless they uncomment the group; monorepo workspaces see the parity-common / polkadot-sdk-scale savings the moment they do.Test plan
pnpm --filter @understand-anything/core build— cleanpnpm --filter @understand-anything/core exec vitest run src/__tests__/ignore-generator.test.ts— 45/45 pass (4 new Rust tests + thebenches/dir test)pnpm --filter @understand-anything/core test— 866 pass, 2 pre-existing wasm-module failures also present onorigin/main(unrelated: scala-extractor, swift-extractor)pnpm lint— clean.understandignoreon a fixture withbenches/,tests/, plus a colocatedfoo.rs+foo_test.rs— Rust group emitted after Python, all five patterns present,# benches/in the detected-dirs section, all commentedCloses #581