perf(linter/plugins): reduce cost of workspaces by overlookmotel · Pull Request #18758 · oxc-project/oxc

overlookmotel · 2026-01-31T12:20:35Z

Workspaces support (#17809) added overhead on JS side of hashmap lookups. Every call to lintFile has to look up details (e.g. registered rules, rule options) from hashmaps keyed by workspace URI.

Perf

Take a different approach which is optimized for common case of there being only 1 workspace:

At any time there's 1 "current workspace".
Store rules, options, and CWD in top-level vars (back to how it was before refactor(linter/plugins): add napi function createWorkspace and destroyWorkspace #17809).
Switch workspaces only when required. Switching reassigns the values in these top level vars.

Before:

Get rules, options, and CWD from hashmaps keyed by workspace URI.

After:

Quick check "is the current workspace the one we need?".
If so, do nothing - the top-level vars registeredRules, allOptions, and cwd elready contain the right settings for the desired workspace.
If current workspace is not the right one, look up the details for desired workspace in workspaces hash map and write them into the top-level vars.

In CLI, workspaceUri passed to lintFile etc is null, so the quick "in the right workspace?" check is particularly cheap - just null === null. So this reduces the overhead that workspace support adds to CLI to just that 1 instruction.

Add of these functions are entirely synchronous, so there's no possibility of a race where 1 call switches out the values in the top-level vars, while another call is busy using them.

CLI: No call to `createWorkspace`

CLI now doesn't need to call createWorkspace at all. The "are we in right workspace?" check always succeeds, so it's irrelevant whether a workspace has been created or not - workspaces hashmap is never accessed.

So workspaces is now an LSP-only thing.

Bundle

This PR also removes all imports from other files from src-js/workspace/index.ts. It now only imports debugAssert, which is optimized out in release build., leaving no imports at all.

Previously, the imports from other files were causing most of the JS plugins code to get loaded on first call to createWorkspace, which broke the lazy loading optimization - Oxlint CLI and LSP were both loading all the JS plugins code eagerly even if the user doesn't use JS plugins.

With this change, the lazy loading optimization is restored. This is visible in the conformance snapshot change in this PR.

overlookmotel · 2026-01-31T12:20:55Z

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Pull request overview

This PR optimizes workspace management in the JS plugin system by reducing overhead for the common single-workspace case. Instead of looking up workspace data in hash maps on every operation, it maintains a "current workspace" concept and stores data in top-level variables. Switching workspaces only occurs when necessary, making the CLI path (with null workspace URI) extremely fast - just a single null check.

Changes:

Removed eager workspace setup from CLI, enabling lazy loading of JS plugin code
Refactored workspace management to use direct variable access instead of hash map lookups
Introduced a workspace switching mechanism that's optimized for single-workspace and same-workspace scenarios

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
apps/oxlint/src/lint.rs	Removed CLI workspace setup code since CLI no longer needs to call `createWorkspace`
apps/oxlint/src-js/workspace/index.ts	Refactored workspace management with current workspace tracking and removed imports to enable lazy loading
apps/oxlint/src-js/plugins/workspace.ts	New file implementing workspace switching logic with fast-path optimization
apps/oxlint/src-js/plugins/options.ts	Converted from Map-based to direct variable access, integrated workspace switching
apps/oxlint/src-js/plugins/load.ts	Converted from Map-based to direct variable access for rules, integrated workspace switching
apps/oxlint/src-js/plugins/lint.ts	Updated to use workspace switching instead of hash map lookups
apps/oxlint/src-js/plugins/context.ts	Separated CWD management from file context setup to support workspace switching
apps/oxlint/src-js/package/rule_tester.ts	Removed workspace creation/destruction, simplified cleanup logic
apps/oxlint/conformance/snapshots/stylistic.md	Updated stack traces reflecting bundle restructuring from lazy loading optimization

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apps/oxlint/src-js/plugins/options.ts

apps/oxlint/src-js/plugins/load.ts

apps/oxlint/src-js/plugins/lint.ts

apps/oxlint/src-js/plugins/context.ts

overlookmotel · 2026-01-31T14:39:27Z

CI is failing on #18763, but that's probably not related to the changes in that PR. VSCode task didn't run on this PR, and I think it's more likely that it's this PR that's actually causing the fail.

VSCode task did run on #18755 lower down the stack, and it passed. And this is the only other PR in the stack which makes significant changes.

EDIT: CI now failing on #18755 too! Seems like it's flaky.

camc314 · 2026-01-31T15:34:06Z

Merge activity

Jan 31, 3:34 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 31, 3:34 PM UTC: camc314 added this pull request to the Graphite merge queue.
Jan 31, 3:34 PM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #18756.
Jan 31, 3:34 PM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #18756.
Jan 31, 3:36 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 31, 3:42 PM UTC: graphite-app added this pull request to the Graphite merge queue.
Jan 31, 4:26 PM UTC: Merged by the Graphite merge queue.

Workspaces support (#17809) added overhead on JS side of hashmap lookups. Every call to `lintFile` has to look up details (e.g. registered rules, rule options) from hashmaps keyed by workspace URI. ### Perf Take a different approach which is optimized for common case of there being only 1 workspace: * At any time there's 1 "current workspace". * Store rules, options, and CWD in top-level vars (back to how it was before #17809). * Switch workspaces only when required. Switching reassigns the values in these top level vars. Before: * Get rules, options, and CWD from hashmaps keyed by workspace URI. After: * Quick check "is the current workspace the one we need?". * If so, do nothing - the top-level vars `registeredRules`, `allOptions`, and `cwd` elready contain the right settings for the desired workspace. * If current workspace is not the right one, look up the details for desired workspace in `workspaces` hash map and write them into the top-level vars. In CLI, `workspaceUri` passed to `lintFile` etc is `null`, so the quick "in the right workspace?" check is particularly cheap - just `null === null`. So this reduces the overhead that workspace support adds to CLI to just that 1 instruction. Add of these functions are entirely synchronous, so there's no possibility of a race where 1 call switches out the values in the top-level vars, while another call is busy using them. ### CLI: No call to `createWorkspace` CLI now doesn't need to call `createWorkspace` at all. The "are we in right workspace?" check always succeeds, so it's irrelevant whether a workspace has been created or not - `workspaces` hashmap is never accessed. So workspaces is now an LSP-only thing. ### Bundle This PR also removes all imports from other files from `src-js/workspace/index.ts`. It now only imports `debugAssert`, which is optimized out in release build., leaving no imports at all. Previously, the imports from other files were causing most of the JS plugins code to get loaded on first call to `createWorkspace`, which broke the lazy loading optimization - Oxlint CLI and LSP were both loading all the JS plugins code eagerly even if the user doesn't use JS plugins. With this change, the lazy loading optimization is restored. This is visible in the conformance snapshot change in this PR.

# Oxlint ### 💥 BREAKING CHANGES - b34a155 linter/plugins: [**BREAKING**] `RuleTester` set `context.filename` to absolute path (#18702) (overlookmotel) ### 🚀 Features - 1753209 linter/vscode: Run extension when JS configs are detected (#18832) (camc314) - c962dd2 linter/lsp: Implement support for oxlint.config.ts (#18826) (camc314) - da32203 linter: Auto generate oxlint.config.ts types (#18597) (camc314) - 19b4df7 oxlint: Introduce `defineConfig` helper (#18596) (camc314) - ea97231 linter: Implement `oxlint.config.ts` support (#17563) (camc314) - 17ca42d linter: Implement `react/no-multi-comp` rule. (#18794) (connorshea) - 88f30e0 linter/plugins: Move eslint compatible plugin conversion to `eslintCompatPlugin` function (#18791) (overlookmotel) - 2a72794 linter/plugins: `RuleTester` take `cwd` property (#18756) (overlookmotel) - 9f533db linter: Add `find_prev_token_within` method for token search (#18769) (camc314) - 772ea70 linter: Introduce `load_js_configs` napi callback (#18767) (camc314) - e9690c1 linter: Introduce `DiscoveredConfig` in preparation for JS configs (#18674) (camc314) - 558b588 linter/prefer-namespace-keyword: Move to correctness (#18733) (camc314) - 7a5c268 oxlint/lsp: Support `jsPlugins` (#17840) (Sysix) - c07497c linter/prefer-modern-dom-apis: Implement suggestion (#17965) (Mikhail Baev) - 8531bc9 linter: Implement `prefer-const` (#18687) (camchenry) - 8670b18 parser: Error on ambient class accessor implementations (#18592) (camc314) - 6b8a5ae linter: Add `eslint-plugin-import/no-nodejs-modules` rule (#18006) (Mikhail Baev) - 04f400d linter/no-duplicates: Add support for `considerQueryString` option (#18657) (camc314) - 3b7f260 linter/consistent-generic-constructor: Implement fixer (#18616) (camc314) - 794f9e4 linter/prefer-exponentation-operator: Implement suggestion (#18602) (camc314) - 773d916 linter: `eslint/sort_keys` ignore leading and trailing spreads in auto-fix (#18485) (Lonami) - 20d4ede linter: Implement `import/no-relative-parent-imports` rule (#18513) (Valentin Maerten) - 0da45ef vscode: Fallback to globally installed oxlint/oxfmt packages (#18007) (Sysix) ### 🐛 Bug Fixes - a3417b1 linter/plugins: Clear state when reloading workspace (#18837) (overlookmotel) - c879992 linter: Error on arrays passed in as config (#18822) (camc314) - 5c80422 linter/tsdown: Ensure relative path for globals import starts with `./` (#18820) (camc314) - 7419dfb linter: Remove invalid debug assersion, add test (#18819) (camc314) - 0ca6269 ci: Fix the repo path normalization logic for tests on Windows. (#18815) (connorshea) - c7b0a65 linter: Fix config option docs for `react/jsx-boolean-value` rule. (#18811) (connorshea) - cce374e linter/prefer-const: Replace entire declaration over just the `let` kw (#18814) (camc314) - 41f92d1 linter: Error when given config options for a lint rule that has no config options defined. (#18809) (connorshea) - 0867a36 linter/consistent-index-object-style: False positive with mapped + generic types (#18801) (camc314) - 1d34b42 linter: Fix 32 bit build (#18783) (camc314) - 95df577 linter/plugins: Handle error from `destroyWorkspace` (#18763) (overlookmotel) - b3261dc linter: Fix the curly rule config to enforce the shape of the config and emit correct docs (#18743) (connorshea) - d981978 linter/plugins: Use non-blocking mode when calling `destroyWorkspace` (#18762) (overlookmotel) - 3f43d4c linter: Accept bools as valid values for `fixable` (#18772) (camc314) - 005910a linter/plugins: Support plugins outside of workspace (#18755) (overlookmotel) - fd92711 vscode: Use `fsPath` for workspace mapping (#18728) (Sysix) - 358b2c1 linter/consistent-generic-constructors: Check bounds when searching for `:` token (#18745) (connorshea) - abd0c28 linter/capitalized-comments: Fix generated rule option docs (#18748) (connorshea) - d90a9f6 linter: Add more tests for `prefer-const`'s fixer and fix its invalid behavior. (#18747) (connorshea) - f82011b oxlint/lsp: Disable JS plugins support in LSP except in tests (#18727) (overlookmotel) - 94505c8 linter/jest: Change `prefer-spy-on` autofix to suggestion (#18152) (Ben Lowery) - 6ec1112 linter: Mark unused disable directive fix as suggestion (#18703) (ddmoney420) - 49609ec linter/no-useless-constructor: Consider argument transformation as used (#18706) (ddmoney420) - 40218de linter: Fix behavior of jsx-a11y/no-static-element-interactions rule. (#17817) (connorshea) - db9751d linter/no-html-link-for-pages: Handle `target=_blank` correctly (#18693) (camc314) - e440b78 linter/plugins: Pass all args to CFG event handlers when 2 rules use same handler (#18683) (overlookmotel) - b393430 linter/curly: Fix multi-or-nest and consistent conflict (#18660) (camc314) - 2e1fbc2 linter/plugins: Implement `context.parserPath` (#18644) (overlookmotel) - 34951ed linter/plugins: `filename` option takes precedence over `parserOptions.lang` in `RuleTester` (#18643) (overlookmotel) - 28df160 linter/plugins: Allow line number passed to `report` to be 0 (#18642) (overlookmotel) - 14fabec vscode: Use built-in `getWorkspaceFolder` for detecting the right workspace of a given uri (#18583) (Sysix) - 0ff4cea oxlint/cli: Report error when nested config could not be parsed (#18504) (Sysix) ### ⚡ Performance - 9862224 linter/plugins: Reduce cost of workspaces (#18758) (overlookmotel) - 6bc0bde linter: Remove string allocation (#18725) (overlookmotel) - 3a6b41e linter/plugins: Replace ESLint Traverser with lightweight traverseNode (#18529) (Rintaro Itokawa) ### 📚 Documentation - dd1a653 linter: Fix doc comment for ignoreStateless config option. (#18808) (connorshea) - 5909085 linter/plugins: Add doc comments (#18753) (overlookmotel) - ffe53a3 linter: Update lint function docs (#18766) (camc314) - b82faec linter: Glob for any css module for no-unassigned-import (#18713) (Ben Stickley) - cd86347 linter: Mark some react rules as unsupported, misc docs improvements (#18617) (connorshea) - 23401d8 linter: Update fixes and suggestions status for tsgolint rules (#18619) (camchenry) # Oxfmt ### 🚀 Features - ee30de9 oxfmt: Add config migration from biome (#18638) (Luca Fischer) ### 🐛 Bug Fixes - e754b18 oxfmt/migrate-prettier: Set `experimentalSortPackagejson: false` by default (#18831) (leaysgur) - a83c266 formatter: Keep decorated function pattern hugged when params break (#18830) (Dunqing) - 0c8efe1 formatter: Quote numeric property keys with `quoteProps: consistent` (#18803) (Dunqing) - 9c14c3e formatter: Ignore comment does not work for sequence expressions in arrow function body (#18799) (Dunqing) - 54984ae formatter: Handle leading comments in arrow function sequence expressions (#18798) (Dunqing) - 61bb2b5 formatter: Correctly expand JSX returned from arrow callbacks in JSX expression containers (#18797) (Dunqing) - 34ee194 formatter: Tailwindcss sorting doesn't work for object property keys (#18773) (Dunqing) - 48f1e35 oxfmt: Prevent ThreadsafeFunction crash on Node.js exit (#18723) (Boshen) - e96adca formatter: Follow Prettier's approach for for-in initializer parentheses (#18695) (Dunqing) - 1215a6f formatter: Preserve quote for class property key in TypeScript (#18692) (Dunqing) - 059acae formatter: Incorrect comments placement for union type in `TSTypeIntersection` (#18690) (Dunqing) - c3d05c1 formatter,oxfmt: Handle CRLF with embedded formatting (#18686) (leaysgur) - 7cb3085 formatter: Preserve comments on rest elements (#18649) (Dunqing) - 21984dd formatter: Preserve type cast comments on rest parameters (#18648) (Dunqing) - 2f70254 formatter: Don't add extra semicolon on suppressed class properties (#18631) (Dunqing) - ac1ff4e oxfmt: Use `empty_line` IR for empty xxx-in-js line (#18623) (leaysgur) - 8f76900 oxfmt: Dedent xxx-in-js templates before calling prettier (#18622) (leaysgur) - 6b726ef oxfmt: Trim whitespace only xxx-in-js templates (#18621) (leaysgur) Co-authored-by: camc314 <18101008+camc314@users.noreply.github.com>

github-actions bot added A-linter Area - Linter A-cli Area - CLI A-linter-plugins Area - Linter JS plugins labels Jan 31, 2026

overlookmotel mentioned this pull request Jan 31, 2026

refactor(linter/plugins): move imports to top level #18759

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github-actions bot added the C-performance Category - Solution not expected to change functional behavior, only performance label Jan 31, 2026

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overlookmotel force-pushed the om/01-31-perf_linter_plugins_reduce_cost_of_workspaces branch from ac826e7 to 7778e54 Compare January 31, 2026 13:49

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overlookmotel mentioned this pull request Jan 31, 2026

language server: JS Plugins support #18662

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refactor(linter/plugins): remove experimental warning #18771

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Boshen mentioned this pull request Feb 2, 2026

release(apps): oxlint v1.43.0 && oxfmt v0.28.0 #18843

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perf(linter/plugins): reduce cost of workspaces#18758

perf(linter/plugins): reduce cost of workspaces#18758
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CLI: No call to createWorkspace

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overlookmotel commented Jan 31, 2026 •

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CLI: No call to `createWorkspace`

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