perf(linter/typescript/array-type): remove full source text clone by mds-ant · Pull Request #23751 · oxc-project/oxc

mds-ant · 2026-06-24T09:10:12Z

What

check_and_report_error_generic in the typescript/array-type rule cloned the entire source file via ctx.source_text().to_string() on every TSArrayType violation, only to use the result as a &str (passed to get_message_type and sliced in the fixer closure). ctx.source_text() already returns &'a str tied to the arena lifetime, so the heap copy is pure waste.

Change

Drop .to_string(); use the borrowed &str directly.

-    let source_text = ctx.source_text().to_string();
+    let source_text = ctx.source_text();
     ...
-    let message_type = get_message_type(type_param, &source_text);
+    let message_type = get_message_type(type_param, source_text);

Impact

Around 1.61 GB of heap allocations saved when running against the microsoft/vscode repo (10,572 files).

Measured by linting with {"typescript/array-type": ["error", {"default": "generic"}]} as the only enabled rule — 40,426 violations across 5,744 files. Release build, glibc system allocator, 3 interleaved runs after warmup, medians reported.

Peak RSS (`getrusage` `ru_maxrss`)

	baseline	this branch	Δ (abs)	Δ (%)
threads=1	362,236 KB	332,740 KB	−29,496 KB	−8.1%
threads=64	489,180 KB	459,732 KB	−29,448 KB	−6.0%

Total heap bytes allocated (`LD_PRELOAD` malloc/calloc/realloc counter)

	baseline	this branch	Δ (abs)	Δ (%)
malloc calls	4,552,293	4,511,867	−40,426	−0.9%
bytes	6,502,015,003	4,893,067,752	−1,608,947,251	−24.7%

The −40,426 calls exactly equals the diagnostic count (one .to_string() per violation).

Wall clock

	baseline	this branch	Δ (abs)	Δ (%)
threads=1	4.152 s	4.122 s	−0.030 s	−0.7%
threads=64	2.695 s	2.588 s	−0.107 s	−4.0%

Verification

cargo test -p oxc_linter --lib array_type passes.

This PR was assisted by Claude Code.

`check_and_report_error_generic` cloned the entire source file via `ctx.source_text().to_string()` only to pass it as `&str` to `get_message_type` and slice it in the fixer closure. `ctx.source_text()` already returns `&'a str`, so the heap copy is unnecessary.

camc314

nice find - thanks!

codspeed-hq · 2026-06-24T09:36:59Z

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 66 skipped benchmarks¹

_{Comparing mds-ant:perf/array-type-full-source-clone-auto (6d246fa) with main (e1886a0)}

66 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

# Oxlint ### 💥 BREAKING CHANGES - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) ### 🚀 Features - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - 1c8f50c linter: Add schema for `eslint/no-restricted-import` (#23642) (Sysix) ### 🐛 Bug Fixes - 7cb85c4 linter/eslint/no-negated-condition: Add autofix for negated conditions (#23825) (Yagiz Nizipli) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d891990 linter/jsx-a11y/role-supports-aria-props: Ignore nullish prop values (#23865) (Mikhail Baev) - 94b6599 linter: Deduplicate missing plugin errors (#23853) (camc314) - eff3eff linter/oxc/branches-sharing-code: Avoid else-if false positives (#23843) (camc314) - 2a2d3b9 linter/eslint/prefer-destructuring: Skip `AssignmentExpression` autofixes (#23818) (camc314) - ddc24ae linter/eslint/id-length: Respect checkGeneric for mapped type keys (#23802) (bab) - cd89202 linter/react/exhaustive-deps: Skip wrapper expression when analyzing hook initializers (#23793) (camc314) - 20e8285 linter/unicorn/prefer-native-coercion-function: Allow ts type predicates (#23774) (camc314) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) - 52032cf linter: Newline-terminate tsgolint errors (#23762) (Mikhail Baev) - 368fda7 linter/eslint/no-warning-comments: Avoid dropping generated regex patterns (#23741) (camc314) - ce44fbd linter/valid-title: Escape disallowed words regex (#23742) (camc314) - 3100d11 linter/prefer-called-exactly-once-with: Avoid out-of-bounds slice panic at end of file (#23625) (Jerry Zhao) - 742be36 refactor/node/handle-callback-err: Reject invalid regex config (#23740) (camc314) - d7be179 linter/eslint/no-restricted-globals: Handle shadowed locals (#23736) (camc314) - b3b1ff8 linter/vitest/expect-expect: Handle global vitest detection correctly (#23734) (camc314) ### ⚡ Performance - 68f9472 linter/jsx-a11y: Skip lowercasing non-aria attribute names (#23906) (Lawrence Lin) - b9312b4 linter/unicorn/prefer-export-from: Use keyed binding lookup (#23893) (Marius Schulz) - cd5204e linter/typescript/no-unsafe-declaration-merging: Use keyed binding lookup (#23894) (Marius Schulz) - e948498 linter/eslint/prefer-named-capture-group: Only dispatch for relevant node types (#23868) (Connor Shea) - 4ac7a8e linter/eslint/max-depth: Derive node types (#23896) (Connor Shea) - daeed09 linter/eslint/no-restricted-globals: Only scan unresolved references (#23890) (camc314) - e808514 linter/jest-vitest: Speed up no-standalone-expect (#23883) (camc314) - 8b165e5 linter/react/exhaustive-deps: Skip non-reactive calls early (#23882) (camc314) - 54005e7 linter/eslint/no-unused-vars: Precompute exported bindings (#23881) (camc314) - 9bc2f8c linter/unicorn/prefer-number-properties: Speed up global checks (#23880) (camc314) - 4ff104f linter: Optimize `require-hook` and `prefer-mock-*` rules to run on specific node types (#23871) (Connor Shea) - cc2213b linter: Run `no-underscore-dangle` only when relevant node types are present (#23867) (Connor Shea) - 3e55c21 linter/promise/always-return: Narrow to function node types (#23878) (Connor Shea) - 7136182 linter/jest-vitest: Speed up no-commented-out-tests (#23864) (camc314) - f138264 linter/eslint/no-script-url: Match javascript: prefix without allocating (#23861) (Lawrence Lin) - 7ef6895 linter/react/no-array-index-key: Delay index symbol lookup (#23857) (camc314) - 26bc171 linter/react/no-array-index-key: Match callback methods directly (#23856) (camc314) - 44fbbda linter/jsx-a11y/interactive-supports-focus: Check cheap conditions first (#23854) (camc314) - 84a5aa3 linter/eslint/no-extend-native: Skip lowercase references early (#23851) (camc314) - 88a74b2 linter/eslint/no-nonoctal-decimal-escape: Scan decimal escapes as bytes (#23850) (camc314) - fca69a8 linter: Skip traversal without this expressions (#23845) (camc314) - 838fd63 linter: Reduce preallocation for per-file diagnostics `Vec` (#23705) (Marius Schulz) - 417b506 linter/typescript/array-type: Remove full source text clone (#23751) (Marius Schulz) ### 📚 Documentation - 57e4469 linter/unicorn: Update prefer-dom-node-text-content rationale (#23933) (Mikhail Baev) - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) # Oxfmt ### 💥 BREAKING CHANGES - 259e0cd oxfmt,formatter_graphql: [**BREAKING**] Support draft syntax with removing prettier fallback (#23326) (leaysgur) - accbc49 oxfmt: [**BREAKING**] Format `parser:css,less,scss` files + css-in-js by `oxc_formatter_css` (#23321) (leaysgur) ### 🚀 Features - dffa4b3 formatter_css: Implement `oxc_formatter_css` (#23320) (leaysgur) - 01de9ec oxfmt: Format `parser:graphql` files by `oxc_formatter_graphql` (#23318) (leaysgur) - 4e66212 formatter_graphql: Implement oxc_formatter_graphql (#23317) (leaysgur) ### 🐛 Bug Fixes - 67325ae formatter_css: Handle frontmatter language (#23819) (leaysgur) - 3f355e5 formatter_graphql: Improve major prettier diffs (#23419) (leaysgur) - 48e2d78 formatter_css: Improve major prettier diffs (#23327) (leaysgur) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) ### ⚡ Performance - 4ddcba0 formatter_core: Add printable-ASCII fast path to TextWidth (#23913) (Lawrence Lin) ### 📚 Documentation - b4d0dc9 oxfmt,formatter,formatter_css,formatter_core: Update AGENTS.md (#23814) (leaysgur) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

…3751) ## What `check_and_report_error_generic` in the `typescript/array-type` rule cloned the entire source file via `ctx.source_text().to_string()` on every `TSArrayType` violation, only to use the result as a `&str` (passed to `get_message_type` and sliced in the fixer closure). `ctx.source_text()` already returns `&'a str` tied to the arena lifetime, so the heap copy is pure waste. ## Change Drop `.to_string()`; use the borrowed `&str` directly. ```diff - let source_text = ctx.source_text().to_string(); + let source_text = ctx.source_text(); ... - let message_type = get_message_type(type_param, &source_text); + let message_type = get_message_type(type_param, source_text); ``` ## Impact Around **1.61 GB** of heap allocations saved when running against the `microsoft/vscode` repo (10,572 files). Measured by linting with `{"typescript/array-type": ["error", {"default": "generic"}]}` as the only enabled rule — 40,426 violations across 5,744 files. Release build, glibc system allocator, 3 interleaved runs after warmup, medians reported. ### Peak RSS (`getrusage` `ru_maxrss`) | | baseline | this branch | Δ (abs) | Δ (%) | |-------------|-----------:|------------:|-----------:|-------:| | threads=1 | 362,236 KB | 332,740 KB | −29,496 KB | −8.1% | | threads=64 | 489,180 KB | 459,732 KB | −29,448 KB | −6.0% | ### Total heap bytes allocated (`LD_PRELOAD` malloc/calloc/realloc counter) | | baseline | this branch | Δ (abs) | Δ (%) | |--------------|--------------:|--------------:|---------------:|-------:| | malloc calls | 4,552,293 | 4,511,867 | −40,426 | −0.9% | | bytes | 6,502,015,003 | 4,893,067,752 | −1,608,947,251 | −24.7% | The −40,426 calls exactly equals the diagnostic count (one `.to_string()` per violation). ### Wall clock | | baseline | this branch | Δ (abs) | Δ (%) | |-------------|---------:|------------:|---------:|------:| | threads=1 | 4.152 s | 4.122 s | −0.030 s | −0.7% | | threads=64 | 2.695 s | 2.588 s | −0.107 s | −4.0% | ## Verification - `cargo test -p oxc_linter --lib array_type` passes. This PR was assisted by Claude Code. Co-authored-by: Cameron <cameron.clark@hey.com>

# Oxlint ### 💥 BREAKING CHANGES - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) ### 🚀 Features - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - 1c8f50c linter: Add schema for `eslint/no-restricted-import` (#23642) (Sysix) ### 🐛 Bug Fixes - 7cb85c4 linter/eslint/no-negated-condition: Add autofix for negated conditions (#23825) (Yagiz Nizipli) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d891990 linter/jsx-a11y/role-supports-aria-props: Ignore nullish prop values (#23865) (Mikhail Baev) - 94b6599 linter: Deduplicate missing plugin errors (#23853) (camc314) - eff3eff linter/oxc/branches-sharing-code: Avoid else-if false positives (#23843) (camc314) - 2a2d3b9 linter/eslint/prefer-destructuring: Skip `AssignmentExpression` autofixes (#23818) (camc314) - ddc24ae linter/eslint/id-length: Respect checkGeneric for mapped type keys (#23802) (bab) - cd89202 linter/react/exhaustive-deps: Skip wrapper expression when analyzing hook initializers (#23793) (camc314) - 20e8285 linter/unicorn/prefer-native-coercion-function: Allow ts type predicates (#23774) (camc314) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) - 52032cf linter: Newline-terminate tsgolint errors (#23762) (Mikhail Baev) - 368fda7 linter/eslint/no-warning-comments: Avoid dropping generated regex patterns (#23741) (camc314) - ce44fbd linter/valid-title: Escape disallowed words regex (#23742) (camc314) - 3100d11 linter/prefer-called-exactly-once-with: Avoid out-of-bounds slice panic at end of file (#23625) (Jerry Zhao) - 742be36 refactor/node/handle-callback-err: Reject invalid regex config (#23740) (camc314) - d7be179 linter/eslint/no-restricted-globals: Handle shadowed locals (#23736) (camc314) - b3b1ff8 linter/vitest/expect-expect: Handle global vitest detection correctly (#23734) (camc314) ### ⚡ Performance - 68f9472 linter/jsx-a11y: Skip lowercasing non-aria attribute names (#23906) (Lawrence Lin) - b9312b4 linter/unicorn/prefer-export-from: Use keyed binding lookup (#23893) (Marius Schulz) - cd5204e linter/typescript/no-unsafe-declaration-merging: Use keyed binding lookup (#23894) (Marius Schulz) - e948498 linter/eslint/prefer-named-capture-group: Only dispatch for relevant node types (#23868) (Connor Shea) - 4ac7a8e linter/eslint/max-depth: Derive node types (#23896) (Connor Shea) - daeed09 linter/eslint/no-restricted-globals: Only scan unresolved references (#23890) (camc314) - e808514 linter/jest-vitest: Speed up no-standalone-expect (#23883) (camc314) - 8b165e5 linter/react/exhaustive-deps: Skip non-reactive calls early (#23882) (camc314) - 54005e7 linter/eslint/no-unused-vars: Precompute exported bindings (#23881) (camc314) - 9bc2f8c linter/unicorn/prefer-number-properties: Speed up global checks (#23880) (camc314) - 4ff104f linter: Optimize `require-hook` and `prefer-mock-*` rules to run on specific node types (#23871) (Connor Shea) - cc2213b linter: Run `no-underscore-dangle` only when relevant node types are present (#23867) (Connor Shea) - 3e55c21 linter/promise/always-return: Narrow to function node types (#23878) (Connor Shea) - 7136182 linter/jest-vitest: Speed up no-commented-out-tests (#23864) (camc314) - f138264 linter/eslint/no-script-url: Match javascript: prefix without allocating (#23861) (Lawrence Lin) - 7ef6895 linter/react/no-array-index-key: Delay index symbol lookup (#23857) (camc314) - 26bc171 linter/react/no-array-index-key: Match callback methods directly (#23856) (camc314) - 44fbbda linter/jsx-a11y/interactive-supports-focus: Check cheap conditions first (#23854) (camc314) - 84a5aa3 linter/eslint/no-extend-native: Skip lowercase references early (#23851) (camc314) - 88a74b2 linter/eslint/no-nonoctal-decimal-escape: Scan decimal escapes as bytes (#23850) (camc314) - fca69a8 linter: Skip traversal without this expressions (#23845) (camc314) - 838fd63 linter: Reduce preallocation for per-file diagnostics `Vec` (#23705) (Marius Schulz) - 417b506 linter/typescript/array-type: Remove full source text clone (#23751) (Marius Schulz) ### 📚 Documentation - 57e4469 linter/unicorn: Update prefer-dom-node-text-content rationale (#23933) (Mikhail Baev) - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) # Oxfmt ### 💥 BREAKING CHANGES - 259e0cd oxfmt,formatter_graphql: [**BREAKING**] Support draft syntax with removing prettier fallback (#23326) (leaysgur) - accbc49 oxfmt: [**BREAKING**] Format `parser:css,less,scss` files + css-in-js by `oxc_formatter_css` (#23321) (leaysgur) ### 🚀 Features - dffa4b3 formatter_css: Implement `oxc_formatter_css` (#23320) (leaysgur) - 01de9ec oxfmt: Format `parser:graphql` files by `oxc_formatter_graphql` (#23318) (leaysgur) - 4e66212 formatter_graphql: Implement oxc_formatter_graphql (#23317) (leaysgur) ### 🐛 Bug Fixes - 67325ae formatter_css: Handle frontmatter language (#23819) (leaysgur) - 3f355e5 formatter_graphql: Improve major prettier diffs (#23419) (leaysgur) - 48e2d78 formatter_css: Improve major prettier diffs (#23327) (leaysgur) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - f7d1f50 oxlint, oxfmt: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate (#23886) (overlookmotel) - d86f60b lsp: Normalize user config path to watch pattern (#23723) (Sysix) ### ⚡ Performance - 4ddcba0 formatter_core: Add printable-ASCII fast path to TextWidth (#23913) (Lawrence Lin) ### 📚 Documentation - b4d0dc9 oxfmt,formatter,formatter_css,formatter_core: Update AGENTS.md (#23814) (leaysgur) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

mds-ant requested a review from camc314 as a code owner June 24, 2026 09:10

camc314 changed the title ~~perf(linter): drop full-source clone in array_type rule~~ perf(linter/typescript/array-type): remove full source text clone Jun 24, 2026

camc314 self-assigned this Jun 24, 2026

camc314 added the A-linter Area - Linter label Jun 24, 2026

Merge branch 'main' into perf/array-type-full-source-clone-auto

6d246fa

camc314 approved these changes Jun 24, 2026

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camc314 merged commit 417b506 into oxc-project:main Jun 24, 2026
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oxc-guard Bot mentioned this pull request Jun 29, 2026

release(apps): oxlint v1.72.0 && oxfmt v0.57.0 #23935

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perf(linter/typescript/array-type): remove full source text clone#23751

perf(linter/typescript/array-type): remove full source text clone#23751
camc314 merged 2 commits into
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mds-ant:perf/array-type-full-source-clone-auto

mds-ant commented Jun 24, 2026 •

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codspeed-hq Bot commented Jun 24, 2026

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mds-ant commented Jun 24, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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codspeed-hq Bot commented Jun 24, 2026

Merging this PR will not alter performance

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mds-ant commented Jun 24, 2026 •

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Total heap bytes allocated (`LD_PRELOAD` malloc/calloc/realloc counter)