fix(linter): detect Svelte TS and module scripts correctly by mustafa0x · Pull Request #20819 · oxc-project/oxc

mustafa0x · 2026-03-28T12:32:35Z

Summary

parse Svelte <script> attributes instead of broad substring checks
detect both module and context="module" scripts when creating partial JS sources
add unit and CLI coverage for module/instance scripts in both JS and TS

Validation

mise x -- cargo test -p oxlint lint_svelte_
mise x -- cargo test -p oxc_linter partial_loader::svelte

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camc314

Do you mind explaining a little bit more about this change - was something not working previously that this now fixes?

mustafa0x · 2026-03-30T04:11:44Z

This PR fixes real Svelte parsing correctness issues in oxlint’s partial-loader path.

Previously, TypeScript detection used a broad content.contains("ts") check on the whole <script ...> tag text, which could misclassify plain JS blocks as TS when "ts" appeared in unrelated attributes or values. It also treated only ' ' and '>' as valid characters after <script, so valid tags like <script\nlang="ts"> or <script\tcontext="module"> could be skipped entirely, causing missed diagnostics.

This change makes parsing attribute-aware (lang, module, context="module"), accepts general whitespace after <script, preserves offsets/module behavior, and adds unit + CLI regression coverage (including newline/tab and TS/module script cases).

camc314 · 2026-03-30T08:21:04Z

@mustafa0x do you mind sharing a real-world example of when it didn't work before?

mustafa0x · 2026-03-30T09:27:47Z

Thanks for the follow-up. Yes, this fixes a real behavior gap, and I validated it with a negative regression check.

Before this PR, parse_script only accepted ' ' or '>' immediately after <script:

if !self.source_text[*pointer..].starts_with([' ', '>']) {
    return self.parse_script(pointer);
}

That means valid Svelte tags like these could be skipped:

<script
  lang="ts">
  debugger;
</script>

<script	context="module">
  debugger;
</script>

So we could silently miss diagnostics for legitimate .svelte files depending on formatting/whitespace.

What this PR changes

The boundary check now accepts any whitespace (space/tab/newline) or >:

let is_script_tag_boundary = self.source_text[*pointer..]
    .chars()
    .next()
    .is_some_and(|ch| ch.is_whitespace() || ch == '>');

It also keeps the existing <script-...> guard behavior and adds attribute-aware handling for lang, module, and context="module".

Regression proof (negative test)

I validated this by doing a throwaway revert in a temporary worktree:

kept all new tests
reverted only the whitespace boundary logic back to the old starts_with([' ', '>']) check
ran:

mise x -- cargo test -p oxc_linter partial_loader::svelte

Result: tests fail exactly where expected:

loader::partial_loader::svelte::test::test_parse_svelte_script_tag_allows_newline_after_script_name
loader::partial_loader::svelte::test::test_parse_svelte_script_tag_allows_tab_after_script_name

Both failed with called Option::unwrap() on a None value, which confirms the loader failed to extract a script block under those valid formats when the fix is removed.

So this is not just refactoring; it closes a real parsing correctness hole and the new regressions are effective at catching it.

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Copilot

Pull request overview

Improves Svelte <script> parsing in the partial loader so TypeScript and module/context-module scripts are detected reliably, and adds regression coverage to ensure both module + instance blocks are linted with correct locations.

Changes:

Parse Svelte <script> attributes to detect lang, module, and context="module" instead of substring checks.
Ensure extracted partial JS sources use the correct SourceType (TS vs JS and module semantics).
Add unit + CLI tests (and fixtures) covering module/instance scripts in JS and TS.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_linter/src/loader/partial_loader/svelte.rs	Adds attribute parsing for `<script>` blocks and expands unit tests for module/context-module + TS handling.
apps/oxlint/src/tester.rs	Adds a helper to capture non-silent CLI output for assertion-based tests.
apps/oxlint/src/lint.rs	Adds CLI regression tests asserting module + instance scripts both produce diagnostics with correct positions.
apps/oxlint/fixtures/cli/svelte/module-script.svelte	New fixture for `<script module>` + instance script.
apps/oxlint/fixtures/cli/svelte/context-module-script.svelte	New fixture for `<script context="module">` + instance script.
apps/oxlint/fixtures/cli/svelte/context-module-script-ts.svelte	New fixture for context-module + instance scripts using `lang="ts"`.

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janosh · 2026-04-25T21:11:01Z

Svelte support in oxc would be huge! wanted to ask if this PR is still active or stale/superseded? what's the best way for community to help get this shipped?

mustafa0x · 2026-04-27T05:44:56Z

@janosh you can also test my up-to-date fork for svelte

camc314

Thanks!

codspeed-hq · 2026-04-27T09:32:20Z

Merging this PR will not alter performance

✅ 4 untouched benchmarks
⏩ 47 skipped benchmarks¹

_{Comparing mustafa0x:fix/svelte-script-detection-micro (2245b5d) with main (3612db1)²}

47 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. ↩
No successful run was found on main (15ded13) during the generation of this report, so 3612db1 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

# Oxlint ### 💥 BREAKING CHANGES - 502e804 ast: [**BREAKING**] Reduce size of `TSTypePredicateName` (#21711) (overlookmotel) - 5651539 ast: [**BREAKING**] Reduce size of `JSXExpression` (#21710) (overlookmotel) - c44e280 ast: [**BREAKING**] Reduce size of `ArrayExpressionElement` (#21709) (overlookmotel) ### 🚀 Features - b4acdbd linter/vue: Implement no-deprecated-delete-set rule (#21766) (bab) - 613bfef linter: Split jest/prefer-to-contain into a jest and a vitest rule. (#21821) (connorshea) - c629719 linter/vue: Implement no-deprecated-events-api rule (#21793) (Alex Peshkov) - f2a8528 linter: Split jest/require-top-level-describe rule into a Jest and a Vitest rule. (#21822) (connorshea) - ea4b358 linter: Split jest/prefer-todo into a shared rule and a vitest-specific rule. (#21820) (connorshea) - 3a66819 linter: Split jest/no-mocks-import into vitest/no-mocks-import (#21818) (camchenry) - 0b3ffce linter: Split jest/no-large-snapshots into vitest/no-large-snapshots (#21814) (camchenry) - d1cf22e linter: Split jest/no-interpolation-in-snapshots into vitest/no-interpolation-in-snapshots (#21812) (camchenry) - bb0c359 linter: Split jest/no-identical-title into vitest/no-identical-title (#21810) (camchenry) - c26ea41 linter: Split jest/no-hooks into vitest/no-hooks (#21809) (camchenry) - 46b32f2 linter: Split jest/no-focused-tests into vitest/no-focused-tests (#21804) (camchenry) - acf41a8 linter: Split jest/no-duplicate-hooks into vitest/no-duplicate-hooks (#21803) (camchenry) - 54d787f linter: Split jest/no-disabled-tests into vitest/no-disabled-tests (#21802) (camchenry) - 9c9a676 linter/vue: Implement no-deprecated-data-object-declaration rule (#21764) (bab) - 4445855 linter: Split `jest/no-conditional-in-test` into `vitest/no-conditional-in-test` (#21763) (camchenry) - b8604de linter: Split `jest/no-conditional-expect` into `vitest/no-conditional-expect` (#21762) (camchenry) - 0dbd650 linter: Split `jest/no-commented-out-tests` into `vitest/no-commented-out-tests` (#21761) (camchenry) - 7f1a97c linter: Split `jest/no-alias-methods` into `vitest/no-alias-methods` (#21760) (camchenry) - eb97c49 linter: Split `jest/max-nested-describe` into `vitest/max-nested-describe` (#21759) (camchenry) - d870cad linter: Split `jest/max-expects` into `vitest/max-expects` (#21758) (camchenry) - 1b97124 linter/vue: Implement no-deprecated-vue-config-keycodes rule (#21699) (bab) - 5f81883 linter/eslint: Implement `func-name-matching` rule (#21708) (Mikhail Baev) - 348f46c linter: Add `respectEslintDisableDirectives` option (#21384) (Christian Vuerings) - 63ec351 linter: Support nested vite+ config discovery (#21638) (camc314) - 560feb4 linter: Introduce `Vite` variant to `DiscoveredConfigFile` (#21637) (camc314) - 07dc41e linter/eslint: Implement `no-underscore-dangle` rule (#21630) (Paul-Arthur THIERY) - e270d54 linter/react: Impl react/no-did-update-set-state (#17322) (Kenzo Wada) - ca81199 linter/react: Implement `forbid-component-props` rule (#20005) (Mikhail Baev) - 6776403 linter/branches-sharing-code: Move rule from nursery to pedantic (#21621) (camc314) - ce7a4dc linter/no-unreachable: Move rule from nursery to correctness (#21618) (camc314) - e3b5e78 linter/getter-return: Move rule from nursery to correctness (#21617) (camc314) - d3a7e9a linter/unicorn: Implement suggestion for `no-useless-iterator-to-array` rule (#21610) (Mikhail Baev) - a0c883c oxlint/lsp: Add vite plus version to server info (#21587) (Sysix) - 67ff860 linter/no-unknown-property: Support React 19 `precedence` prop (#21590) (João Pedro Schmitz) ### 🐛 Bug Fixes - aace797 linter: Detect Svelte TS and module scripts correctly (#20819) (mustafa0x) - 3612db1 linter/prefer-default-parameters: Skip reporting on object/class setters (#21836) (camc314) - 28c3521 oxlint/lsp: Remove overlapping edits for `source.fixAllDangerous.oxc` code action (#21785) (Sysix) - 705a82c linter/no-non-null-asserted-nullish-coalescing: Add fixer (#21827) (yyh) - 33f5535 linter: Add checks that `Program` is in current allocator chunk before JS plugins linting (#21774) (overlookmotel) - d122877 linter/no-extra-non-null-assertions: Add fixer (#21744) (yyh) - 37f0731 linter: `with_plugin_vitest(true)` working realiable in test mode (#21769) (Said Atrahouch) - e42e6a6 linter/role-supports-aria-props: False positive with `combobox` and `haspopup` (#21725) (Leonabcd123) - e24324f linter: Iframe-has-title false positive for template literals (#21714) (Leonabcd123) - 41a6510 linter/vitest/hoisted-apis-on-top: Only check first member (#20068) (Sidharth Vinod) - 98ed888 linter: Check initializer for allowConstantExport in only-export-components (#20608) (Eyüp Can Akman) - 1946e8b linter: Avoid applying override plugin categories to eslint rules (#21521) (bab) - 3d1e83a linter: Parse `<script>` tag attributes with curly braces in Svelte files (#21089) (bab) - bc6ade5 linter: Report actual disable directive prefix (#21682) (camc314) - bf84466 linter: Respect category settings in overrides (#19411) (Connor Shea) - 52ecb45 linter/vitest: Don't treat `test.extend` or `it.extend` as test functions (#21668) (Said Atrahouch) - aa1a00c linter: Support jsx-a11y attributes setting in anchor-is-valid rule (#21665) (camchenry) - 30e0ad3 linter/prefer-default-parameters: Preserve TS annotations in fixer (#21655) (camc314) - 8c425db linter: Allow string for jest version in config schema (#21649) (camc314) - 3617864 linter/react/display-name: Fix false positive for named default class (#21643) (Mikhail Baev) - f3a02cc linter/no-non-null-assertion: Improve diagnostic message (#21616) (Cameron) - c2ada2c linter: Make `--fix-dangerously` fix dangerous fixes and suggestions as documented (#13366) (Ulrich Stark) - 8265ed9 linter/sort-keys: Handle CRLF separated groups (#21608) (camc314) - 96c559e linter/no-shadow: Add note explaining enum member shadowing (#21607) (camc314) - 3b49389 linter: No-irregular-whitespace: add config options (#21559) (camchenry) ### ⚡ Performance - cdc9eae oxlint/lsp: Avoid clones on lsp options deserializion (#21748) (Sysix) - be2db80 linter/sort-keys: Reduce allocations (#21560) (camchenry) ### 📚 Documentation - 453d647 linter: Remove now-unnecessary compatibility notes from shared Jest/Vitest rules. (#21826) (connorshea) - b1574a2 linter: Fix the configuration docs for no-underscore-dangle rule. (#21801) (connorshea) - 6946aee linter: Remove no-longer-relevant documentation about vitest compatibility from shared Jest/Vitest rules. (#21799) (connorshea) - 0652ea2 linter: Misc grammar cleanup for Vitest rules. (#21755) (connorshea) - 99f0b68 linter: Improve docs for `vitest/require-mock-type-parameters` rule. (#21754) (connorshea) - 9e2796b linter: Improve the docs for the `vitest/hoisted-apis-on-top` rule. (#21753) (connorshea) - 2ccede2 linter: Improve function usage examples in doc comments (#21718) (overlookmotel) - 43adae9 linter: Add version section to rules page (#21601) (camchenry) - d15dad2 linter: Export rule version metadata (#21588) (Old Autumn) # Oxfmt ### 💥 BREAKING CHANGES - 502e804 ast: [**BREAKING**] Reduce size of `TSTypePredicateName` (#21711) (overlookmotel) - 5651539 ast: [**BREAKING**] Reduce size of `JSXExpression` (#21710) (overlookmotel) - c44e280 ast: [**BREAKING**] Reduce size of `ArrayExpressionElement` (#21709) (overlookmotel) ### 🚀 Features - 3bc54a9 oxfmt: Respect nested config for `--stdin-filepath` (#21627) (leaysgur) - 144f27a oxfmt: Respect ignore settings for `--stdin-filepath` (#21625) (leaysgur) - 81c7ae4 oxfmt/lsp: Add vite plus version to server info (#21586) (Sysix) ### 🐛 Bug Fixes - 477435b formatter/sort_imports: Keep leading blank line when decreasing group transitions (#21835) (leaysgur) - 38d1e82 oxfmt/lsp: Format non `file://` URIs without a authority (#21647) (Sysix) - 5eb8e2b formatter/sort_imports: Preserve blank lines around ignored side-effect imports (#21692) (leaysgur) - 0dce3c6 oxfmt: Handle invalid `overrides` config without panic (#21661) (Yuji Sugiura) - 9f82ed4 formatter: Escape backticks in JSDoc inline code spans (#21577) (bab) ### ⚡ Performance - db6c603 oxfmt/lsp: Avoid clones on lsp options deserializion (#21749) (Sysix) - 6a96c76 formatter: Avoid heap alloc for jsdoc delimiter (#21597) (leaysgur) --------- Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron Clark <cameron.clark@hey.com>

benmccann · 2026-04-28T12:17:20Z

When plugin support is added, I wonder how this will interact with eslint-plugin-svelte. I wonder if it's going to cause duplicate checks

mustafa0x · 2026-04-28T14:39:08Z

@camc314 Thanks for the merge!

Should I continue opening small and self-contained PRs for svelte? Or pause for now, especially as a new plugin system is impending?

camc314 · 2026-04-28T14:41:55Z

@camc314 Thanks for the merge!

Should I continue opening small and self-contained PRs for svelte? Or pause for now, especially as a new plugin system is impending?

Thanks for contributing!

Any bug fixes would be much appreciated. But for new features, let's hold until the embedded framework plugins are released! Thanks!

camc314 · 2026-04-28T15:25:32Z

When plugin support is added, I wonder how this will interact with eslint-plugin-svelte. I wonder if it's going to cause duplicate checks

possibly - we'll probably add an optin to disable the built in svelte linting - TBD

fix(linter): detect Svelte TS and module scripts correctly

9900f83

mustafa0x requested a review from camc314 as a code owner March 28, 2026 12:32

github-actions Bot added A-linter Area - Linter A-cli Area - CLI C-bug Category - Bug labels Mar 28, 2026

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Comment thread crates/oxc_linter/src/loader/partial_loader/svelte.rs Outdated

mustafa0x mentioned this pull request Mar 28, 2026

feat(config): support recommended categories and string extends in oxlint.config.ts mustafa0x/oxc#1

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fix(linter): accept whitespace after svelte <script

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Comment thread crates/oxc_linter/src/loader/partial_loader/svelte.rs

fix(linter): support static expression attrs in svelte script

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Comment thread crates/oxc_linter/src/loader/partial_loader/svelte.rs

mustafa0x added 2 commits March 30, 2026 13:36

fix(linter): fallback on unknown svelte script lang

1662bb6

test(linter): cover spaced braced svelte lang attr

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camc314 requested a review from Copilot March 30, 2026 10:48

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fix(linter): avoid recursion while skipping script-like tags

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Comment thread crates/oxc_linter/src/loader/partial_loader/svelte.rs Outdated

docs(linter): clarify svelte script module semantics comment

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This was referenced Apr 3, 2026

migrate repo to oxlint sveltejs/svelte#17665

Open

feat: integrate Svelte support across oxlint and oxfmt #21059

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Merge branch 'main' into fix/svelte-script-detection-micro

c0db5f2

camc314 approved these changes Apr 27, 2026

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fix lint

054fce3

fix lint again

2245b5d

camc314 merged commit aace797 into oxc-project:main Apr 27, 2026
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oxc-guard Bot mentioned this pull request Apr 27, 2026

release(apps): oxlint v1.62.0 && oxfmt v0.47.0 #21838

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mustafa0x commented Mar 28, 2026

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What this PR changes

Regression proof (negative test)

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Merging this PR will not alter performance

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