fix(oxfmt/lsp): prefer language_id over file extension when formatting by Copilot · Pull Request #19977 · oxc-project/oxc

Copilot · 2026-03-03T20:57:37Z

Explore the codebase (apps/oxfmt/src/lsp/, test/lsp/format/)
Make get_file_extension_from_language_id accessible (pub(super)) in mod.rs
Modify format_file in server_formatter.rs to prefer language_id over file extension
Update run_format to pass language_id to format_file
Create test fixture apps/oxfmt/test/lsp/format/fixtures/format/test.ts.txt
Add test case in format.test.ts for .txt file with TypeScript language_id
Update snapshot
Refactor: extract apply_language_id_extension helper shared by both create_fake_file_path_from_language_id and format_file

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Sysix · 2026-03-03T21:15:36Z

@copilot could you refactor create_fake_file_path_from_language_id and the path of it in a more "elegant" way. So we can share the logic more

Copilot · 2026-03-03T21:27:10Z

@copilot could you refactor create_fake_file_path_from_language_id and the path of it in a more "elegant" way. So we can share the logic more

Done in 223cd58. I introduced apply_language_id_extension(language_id, path) -> Option<PathBuf> as the shared primitive — it maps a language_id to an extension and returns a copy of the given path with that extension applied. Both callers now use it:

create_fake_file_path_from_language_id: builds a base path from root + uri.authority(), then calls apply_language_id_extension
format_file: calls apply_language_id_extension(language_id, path) directly, falling back to the original path extension if the language id is unknown

Sysix · 2026-03-03T21:53:15Z

The reasons can be found in #19976 @leaysgur

Copilot

Pull request overview

Updates the oxfmt LSP formatter to choose a formatting strategy based on the LSP language_id (when available) rather than only the on-disk file extension, enabling correct formatting for files whose extension doesn’t match their active language mode.

Changes:

Prefer language_id-derived extensions when selecting FormatFileStrategy for file-backed documents.
Refactor shared language-id-to-extension logic into an apply_language_id_extension helper in the LSP module.
Add a new LSP formatting fixture/test + snapshot for a .txt file formatted as TypeScript via language_id.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
apps/oxfmt/src/lsp/server_formatter.rs	Passes `language_id` into `format_file` and prefers language-id-based strategy detection.
apps/oxfmt/src/lsp/mod.rs	Exposes language-id extension mapping to sibling modules and adds `apply_language_id_extension`.
apps/oxfmt/test/lsp/format/format.test.ts	Adds a new test case covering `.txt` opened as TypeScript.
apps/oxfmt/test/lsp/format/fixtures/format/test.ts.txt	New fixture input for the TypeScript-via-languageId case.
apps/oxfmt/test/lsp/format/snapshots/format.test.ts.snap	Adds the expected snapshot output for the new fixture.

apps/oxfmt/src/lsp/server_formatter.rs

leaysgur · 2026-03-04T00:25:07Z

Merge activity

Mar 4, 12:25 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Mar 4, 12:25 AM UTC: leaysgur added this pull request to the Graphite merge queue.
Mar 4, 12:32 AM UTC: Merged by the Graphite merge queue.

#19977) - [x] Explore the codebase (apps/oxfmt/src/lsp/, test/lsp/format/) - [x] Make `get_file_extension_from_language_id` accessible (pub(super)) in `mod.rs` - [x] Modify `format_file` in `server_formatter.rs` to prefer `language_id` over file extension - [x] Update `run_format` to pass `language_id` to `format_file` - [x] Create test fixture `apps/oxfmt/test/lsp/format/fixtures/format/test.ts.txt` - [x] Add test case in `format.test.ts` for `.txt` file with TypeScript `language_id` - [x] Update snapshot - [x] Refactor: extract `apply_language_id_extension` helper shared by both `create_fake_file_path_from_language_id` and `format_file`  --- 🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. [Learn more about Advanced Security.](https://gh.io/cca-advanced-security)

# Oxlint ### 🚀 Features - e6b604f oxlint: Auto-enable gitlab formatter on GitLab (#20076) (camc314) - 2488a68 linter: Add .oxlintrc.jsonc config file support (#19870) (Scott S.) - 61bf388 linter: Add `options.reportUnusedDisableDirectives` to config file (#19799) (Peter Wagenet) - c92422b oxlint: Auto-enable github formatter on GitHub Actions (#19944) (Boshen) - 0337c6d linter: Implement typescript/no-unecessary-type-conversion (#19955) (camc314) - 2919313 linter: Introduce denyWarnings config options (#19926) (camc314) - a607119 linter: Introduce maxWarnings config option (#19777) (camc314) ### 🐛 Bug Fixes - 0861d9a linter/plugins: Remove getters from `Context` (#20115) (overlookmotel) - 92cfb14 linter/plugins: Fix types for `walkProgram` and `walkProgramWithCfg` (#20081) (overlookmotel) - 10e211f oxlint/lsp: Send other code actions besides `source.fixAll` if requested (#20042) (Sysix) - 602daaa linter/plugins: Fix type definition for `VisitorObject` (#20065) (overlookmotel) - ee0491e apps,napi: Explicitly specify libs in tsconfigs (#20071) (camc314) - b6e9499 linter: Fix the logic for `unicorn/prefer-dom-node-remove` to handle literal callees as well as arguments. (#20059) (connorshea) - 3874ae1 linter: Update `unicorn/prefer-query-selector` to also catch `getElementsByName()`. (#20060) (connorshea) - 77c93fb linter: Handle array-type shorthand inside union members (#20034) (camc314) - 50eb160 linter/no-unused-vars: Allow unused type params in ambient module blocks (#19615) (Don Isaac) - 1dd0d21 linter/no-restricted-imports: Apply regex pattern checks to side-effect imports (#20028) (camc314) - 7f3d735 linter: Error when --type-check is used without --type-aware (#20025) (camc314) - eea201c unicorn/prefer-string-slice: Avoid unsafe autofix for substr-to-slice (#20010) (camc314) - 50359dc oxlint/lsp: Detect `reportUnusedDisableDirectives` from oxlint config, change lsp `unusedDisableDirectives` default value to `None` (#20011) (Sysix) - 4bc84b1 linter/plugins: Allow `null` and `undefined` for `rule.meta.fixable` (#20008) (overlookmotel) - 753e27e linter/role-supports-aria-props: Add `aria-posinset` to supported `option` ARIA properties (#20003) (JongKyung Lee) - f57b2c9 linter/plugins: Fix return types of tokens methods (#19985) (overlookmotel) - 27ee4fc linter/no-loss-of-precision: Avoid double rounding for negative exponents (#19999) (camc314) - 77a94bb linter: Avoid no-loss-of-precision false positive for 3e-308 (#19992) (camc314) - 6245c56 linter/no-unused-private-class-members: Treat logical lhs access as usage (#19991) (camc314) - 65891e3 linter: Avoid prefer-const false positive for mixed-scope destructuring (#19982) (camc314) - 89991fe linter: Avoid prefer-const false positive for operator reassignments (#19975) (camc314) - 87318e7 oxlint/lsp: Load js config with reforcing fs read (#19551) (Sysix) - d40a942 linter/no-useless-constructor: Mark fixer as suggestion (#19961) (camc314) - ccbd959 linter/prefer-code-point: Report String.fromCharCode member references (#19931) (camc314) - 14fbbfc linter: Add help text to oxc/no-rest-spread-properties rule (#19900) (Subin Kim) ### ⚡ Performance - 2baa5fb napi: Unify build-test profile to coverage for cache sharing (#20090) (Boshen) - 77f1c71 linter/plugins: Make tokens class instances (#19980) (overlookmotel) - 758b424 linter/plugins: Reduce memory copies for tokens (#19979) (overlookmotel) - 236847f linter/plugins: Cache token objects (#19978) (overlookmotel) - 94b597a linter/plugins: Store tokens as a `Box<[Token]>` (#19969) (overlookmotel) ### 📚 Documentation - 2c0010a linter/plugins: Move comment about "bivariance hack" into generated code (#20082) (overlookmotel) - 7538f09 linter: Improve `import/extensions` and `import/no-named-as-default` rule docs. (#20053) (connorshea) - 1f909cf linter: Improve docs for `unicorn/require-post-message-target-origin` rule. (#20061) (connorshea) - 12ae35c oxlint/lsp: Remove outdated ToDo for `LintOptions.run` (#20012) (Sysix) - 3be73e6 linter/plugins: Fix JSDoc comments for tokens methods (#20004) (overlookmotel) - 48ef285 linter: Update `--config` docs (#19965) (camc314) - 6ea49a0 linter: Fix some identation issues for the generated types used in `oxlint.config.ts`. (#19942) (connorshea) - 6c0e0b5 linter: Add oxlint.config.ts to the config docs. (#19941) (connorshea) - 160e423 linter: Add a note that the typeAware and typeCheck options require oxlint-tsgolint (#19940) (connorshea) - d54c275 linter: Improve rule docs for 27 unicorn rules (#19903) (connorshea) # Oxfmt ### 🚀 Features - ee26215 oxfmt: Support css-in-js substitution (#20019) (leaysgur) - 0f0ff51 oxfmt: Display default settings was used message in cli stats (#19939) (leaysgur) - 88815b8 oxfmt: Reintroduce stats line for write mode (#19938) (leaysgur) ### 🐛 Bug Fixes - ee0491e apps,napi: Explicitly specify libs in tsconfigs (#20071) (camc314) - 92f4490 oxfmt: Apply `is_ignored_dir` for glob paths too (#20056) (leaysgur) - 114f974 oxfmt/lsp: Prefer language_id over file extension when formatting (#19977) (copilot-swe-agent) ### ⚡ Performance - 2baa5fb napi: Unify build-test profile to coverage for cache sharing (#20090) (Boshen) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

Copilot AI assigned Copilot and Sysix Mar 3, 2026

Copilot started work on behalf of Sysix March 3, 2026 20:57 View session

Copilot AI changed the title ~~[WIP] Update LSP files to prefer language ID~~ feat(oxfmt/lsp): prefer language_id over file extension when formatting Mar 3, 2026

Copilot finished work on behalf of Sysix March 3, 2026 21:10

github-actions bot added A-cli Area - CLI A-formatter Area - Formatter C-enhancement Category - New feature or request labels Mar 3, 2026

Copilot started work on behalf of Sysix March 3, 2026 21:15 View session

Sysix changed the title ~~feat(oxfmt/lsp): prefer language_id over file extension when formatting~~ fix(oxfmt/lsp): prefer language_id over file extension when formatting Mar 3, 2026

Sysix removed the C-enhancement Category - New feature or request label Mar 3, 2026

github-actions bot added the C-bug Category - Bug label Mar 3, 2026

Copilot finished work on behalf of Sysix March 3, 2026 21:27

Sysix marked this pull request as ready for review March 3, 2026 21:53

Copilot AI review requested due to automatic review settings March 3, 2026 21:53

Sysix assigned leaysgur Mar 3, 2026

Sysix approved these changes Mar 3, 2026

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Copilot started reviewing on behalf of Sysix March 3, 2026 21:53 View session

Copilot AI reviewed Mar 3, 2026

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leaysgur approved these changes Mar 4, 2026

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leaysgur added the 0-merge Merge with Graphite Merge Queue label Mar 4, 2026

graphite-app bot force-pushed the copilot/update-lsp-files-prefer-language-id branch from 0140a8e to 114f974 Compare March 4, 2026 00:25

graphite-app bot merged commit 114f974 into main Mar 4, 2026
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graphite-app bot deleted the copilot/update-lsp-files-prefer-language-id branch March 4, 2026 00:32

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Mar 4, 2026

Boshen mentioned this pull request Mar 9, 2026

release(apps): oxlint v1.52.0 && oxfmt v0.37.0 #20143

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Sysix mentioned this pull request Mar 11, 2026

formatter: Different behavior when running from CLI vs IDE format on save oxc-project/oxc-vscode#140

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fix(oxfmt/lsp): prefer language_id over file extension when formatting#19977

fix(oxfmt/lsp): prefer language_id over file extension when formatting#19977
graphite-app[bot] merged 1 commit intomainfrom
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