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fix(formatter): relocate leading comments for single-element union/intersection types#18083

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fix/formatter-union-type-comments
Jan 20, 2026
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fix(formatter): relocate leading comments for single-element union/intersection types#18083
graphite-app[bot] merged 1 commit intomainfrom
fix/formatter-union-type-comments

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@Boshen Boshen commented Jan 16, 2026

Summary

  • For type alias declarations like type A = /*1*/ | C, Prettier relocates the leading comment from before the |/& operator to after the identifier
  • This produces type A /*1*/ = C; instead of type A = /*1*/ C;
  • Handles both union and intersection types with single elements
  • Skips complex nested cases (parenthesized types or same-type nesting) which have different comment handling rules

Test plan

  • cargo run -p oxc_prettier_conformance -- --filter union-parens passes
  • cargo run -p oxc_prettier_conformance -- --filter intersection-parens passes (all 3 tests)
  • TS conformance improved from 584/606 (96.37%) to 587/606 (96.86%)

🤖 Generated with Claude Code

Copilot AI review requested due to automatic review settings January 16, 2026 13:52
@Boshen Boshen requested a review from Dunqing as a code owner January 16, 2026 13:52
@github-actions github-actions bot added A-formatter Area - Formatter C-bug Category - Bug labels Jan 16, 2026
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Pull request overview

This pull request fixes the formatting of single-element union and intersection types in TypeScript type alias declarations when they have leading comments before the operator. The fix relocates comments from before the | or & operator to after the type identifier, matching Prettier's behavior.

Changes:

  • Added special handling in the formatter for single-element union/intersection types with exactly one leading comment
  • The comment is relocated from before the operator (type A = /*1*/ | C) to after the identifier (type A /*1*/ = C)
  • Skips complex nested cases (parenthesized types or same-type nesting) which have different formatting rules

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File Description
tasks/prettier_conformance/snapshots/prettier.ts.snap.md Updates test results showing 3 additional tests now passing (587/606 vs 584/606), specifically union-parens and intersection-parens tests
crates/oxc_formatter/src/utils/assignment_like.rs Adds comment relocation logic for single-element union/intersection types in type alias declarations

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codspeed-hq bot commented Jan 16, 2026

Merging this PR will not alter performance

✅ 38 untouched benchmarks
⏩ 7 skipped benchmarks1


Comparing fix/formatter-union-type-comments (d6bdb9d) with main (a95b9bb)2

Open in CodSpeed

Footnotes

  1. 7 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.

  2. No successful run was found on main (312da18) during the generation of this report, so a95b9bb was used instead as the comparison base. There might be some changes unrelated to this pull request in this report.

@Boshen Boshen force-pushed the fix/formatter-union-type-comments branch from 1d6456c to 07c74c4 Compare January 16, 2026 14:00
@Dunqing Dunqing force-pushed the fix/formatter-union-type-comments branch from 07c74c4 to d6bdb9d Compare January 19, 2026 07:54
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Dunqing commented Jan 19, 2026


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@graphite-app graphite-app bot added the 0-merge Merge with Graphite Merge Queue label Jan 19, 2026
@Boshen Boshen force-pushed the fix/formatter-union-type-comments branch from d6bdb9d to 2710646 Compare January 20, 2026 15:43
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graphite-app bot commented Jan 20, 2026

Merge activity

…tersection types (#18083)

## Summary

- For type alias declarations like `type A = /*1*/ | C`, Prettier relocates the leading comment from before the `|`/`&` operator to after the identifier
- This produces `type A /*1*/ = C;` instead of `type A = /*1*/ C;`
- Handles both union and intersection types with single elements
- Skips complex nested cases (parenthesized types or same-type nesting) which have different comment handling rules

## Test plan

- [x] `cargo run -p oxc_prettier_conformance -- --filter union-parens` passes
- [x] `cargo run -p oxc_prettier_conformance -- --filter intersection-parens` passes (all 3 tests)
- [x] TS conformance improved from 584/606 (96.37%) to 587/606 (96.86%)

🤖 Generated with [Claude Code](https://claude.com/claude-code)
@graphite-app graphite-app bot force-pushed the fix/formatter-union-type-comments branch from 2710646 to 2194552 Compare January 20, 2026 17:09
@graphite-app graphite-app bot merged commit 2194552 into main Jan 20, 2026
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@graphite-app graphite-app bot deleted the fix/formatter-union-type-comments branch January 20, 2026 17:15
@graphite-app graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Jan 20, 2026
overlookmotel pushed a commit that referenced this pull request Jan 26, 2026
# Oxlint
### 💥 BREAKING CHANGES

- 777fc40 ast: [**BREAKING**] Add `Ident` type (#18354) (Boshen)

### 🚀 Features

- 34c3ec3 linter/prefer-logical-operator-over-ternary: Implement fixer
(#18545) (camc314)
- 019e0aa linter/valid-typeof: Add suggestions if type is misspelled
(#18543) (camchenry)
- 704c8eb linter/use-isnan: Add more specific error message for
equality/inequality (#18542) (camchenry)
- 1e99ace linter/use-isnan: Support more `indexOf` cases and improve
diagnostic messages (#18537) (camchenry)
- bffd134 linter/text-encoding-identifier-case: Add `withDash` option
(#18533) (camc314)
- 993fd2b parser: Parse unambiguous await with better error messages
(#18480) (Boshen)
- b4b6247 linter/plugins: `RuleTester` support settings (#18445)
(overlookmotel)
- 15d69dc linter: Implement react/display-name rule (#18426) (camchenry)
- 2fbceae linter: Implement rule docs and config support for rules with
tuple config options. (#18372) (connorshea)
- 8db0e78 linter/plugins: Handle BOMs (#18376) (overlookmotel)
- 6ac09e2 linter/plugins: Support source text not being at start of
buffer (#18375) (overlookmotel)
- fc3c86b linter: Update 125 rules to raise errors when provided with
invalid config options. (#18104) (connorshea)
- 2cc6ad2 linter/plugins: Add `ecmaFeatures` to `parserOptions` (#18313)
(overlookmotel)

### 🐛 Bug Fixes

- 2acf568 linter/plugins: Keep `Infinity` in rule default options
(#18550) (overlookmotel)
- 332d2ef linter/plugins: Add `jsx` property to
`parserOptions.ecmaFeatures` (#18549) (overlookmotel)
- 7d9bb1b linter: Update `eslint/func-names` to error on invalid rule
config options, improve docs. (#18510) (connorshea)
- 9c67974 linter: Improve the jsx-a11y/no-noninteractive-tabindex rule
to match original rule logic better (#17848) (connorshea)
- 75e7163 vscode: Support json5 for oxfmt (#18502) (Sysix)
- c205b0d ast: Remove `ThisExpression` from `TSModuleReference` (#18489)
(Boshen)
- c51339a oxlint/lsp: Respect code action `source.fixAll` as an alias
for `source.fixAll.oxc` (#18366) (Sysix)
- 3c0e9b9 oxlint/lsp: Skip dangerous fixes/suggestions for "fix all"
code action and command (#18364) (Sysix)
- c44c093 linter: Fix behavior of unicorn/catch-error-name to match
original rule (#18209) (connorshea)
- 9c65aff linter/jsx-a11y: Change `no-autofocus` autofix to suggestion
(#18155) (Ben Lowery)
- 235c820 linter/unicorn: Fix `prefer-array-some` autofix for
`.filter().length` pattern (#18153) (Ben Lowery)
- a9925dc linter: Mark fixes in `unicorn/no-null` rule as dangerous.
(#18436) (connorshea)
- cee29b4 linter: Remove confusing scope from
`react/only-export-components` rule diagnostics. (#18434) (connorshea)
- aed3669 parser: Parse HTML-like comments in unambiguous mode (#18442)
(Boshen)
- b8a371d linter: Fix the path used in the gitlab format output (#18165)
(connorshea)
- e046ea6 linter: `vue/no-lifecycle-after-await` skip looking into arrow
functions (#18302) (Sysix)
- a9bfbcf linter: Compatibility issue with `DiagnosticData` type in
ESLint (#18396) (루밀LuMir)
- 10ab424 linter: `react/no_array_index_key` continue search for other
attributes (#18409) (Lonami)
- 9d776d4 linter: Update `import/no-cycle` rule to error on invalid
config options. (#18330) (connorshea)
- c163231 linter: Update eslint/sort-imports to validate options.
(#18378) (connorshea)
- 79bbcff linter: Update `eslint/func-style` to error on invalid
configuration options. (#18390) (connorshea)
- b871235 linter/plugins: Fix identifying "use strict" directives in
scope analysis (#18402) (overlookmotel)
- 5985141 linter: Update `jest/prefer-lowercase-title` rule to error on
invalid config options. (#18332) (connorshea)
- faca4b5 linter/plugins: Tokenize `let`, `static` and `yield` as
`Keyword`s (#18368) (overlookmotel)
- a3914fd linter/plugins: Allow line number passed to `report` to be 1
over line count (#18341) (overlookmotel)
- 88e0896 linter: Update `typescript/no-restricted-types` rule to error
on invalid config options. (#18329) (connorshea)
- 9eec600 linter: Update `react/jsx-fragments` rule to raise an error on
invalid configuration options (#18111) (connorshea)
- 0fa969d linter: Update `react/no-will-update-set-state` to error on
invalid config options (#18112) (connorshea)
- 70e7be4 linter: Update `import/no-unassigned-import` to raise an error
when passed invalid config options. (#18108) (connorshea)
- 496cac7 linter: Update `unicorn/explicit-length-check` to raise an
error when passed invalid config options. (#18107) (connorshea)
- 080b1ec linter: Update 5 more rules to error on invalid config
options. (#18113) (connorshea)
- c5d05dd linter: Update 11 rules to raise an error on invalid config
options. (#18109) (connorshea)
- 9e359d4 linter/plugins: Set all properties on global vars objects
(#18317) (overlookmotel)
- 39c7f32 linter/plugins: Set `writeable` flag on variables where
defined as globals (#18316) (overlookmotel)
- a570693 linter/plugins: Fix `CatchClause` scopes (#18312)
(overlookmotel)
- 8c98e69 linter: `vitest/prefer-describe-function-title`: Check earlier
to avoid false positive (#18177) (Jovi De Croock)
- 44be0eb linter/plugins: Set scope analyse settings based on source
type (#18306) (overlookmotel)
- b9a14fd vscode: Update package.json to restrict a few more config
options. (#18270) (Connor Shea)
- c1260cb vscode: Update version info formatting. (#18274) (connorshea)
- 2f68dc6 vscode: Update notification for client restart to specify
tool. (#18273) (connorshea)

### ⚡ Performance

- dc931ba linter/no-inner-declarations: Skip scope flags lookup in
modules (#18249) (overlookmotel)
- 07618a7 linter: Turn off `scope_build_child_ids` for SemanticBuilder
(#18360) (Dunqing)
- 1aac079 linter/exhaustive-deps: Simplify the logic of checking if the
identifier it is a dependency of hook (#18350) (Dunqing)
- 591d522 linter/block-scoped-var: Avoid `iter_all_scope_child_ids` by
walking references/redeclarations scope ancestors (#18335) (Dunqing)
- 2eefd6d linter/plugins: Remove branch from token parsing (#18369)
(overlookmotel)

### 📚 Documentation

- 698c21d linter: Modernize docs for various React rules (#18559)
(connorshea)
- 314a47c linter: Clarify the `no-find-dom-node` rule with a note that
the method was removed in React 19. (#18556) (connorshea)
- 5eff704 linter: Update `no-inner-declarations` to fix config option
docs (#18511) (connorshea)
- dd5d2f6 linter: Improve diagnostic message in `valid_typeof` rule.
(#18507) (connorshea)
- 8ccd853 npm: Update package homepage URLs and add keywords (#18509)
(Boshen)
- 4958233 linter: Add missing "What it does" section in
prefer-reflect-apply rule. (#18475) (connorshea)
- 2fa83a4 linter: Improve the docs for import/unambiguous. (#18474)
(connorshea)
- 7b1505c linter: Improve docs for `oxc/only-used-in-recursion` rule.
(#18473) (connorshea)
- ab506d6 linter/plugins: Correct comment (#18456) (overlookmotel)
- 4565c73 linter: `react/display-name`: add docs for config options
(#18430) (camchenry)
- b95a89f linter: Fix docs for the curly rule. (#18374) (connorshea)
- f675eb4 linter: Fix the `react/only-export-components` rule docs.
(#18319) (connorshea)
- 704db95 linter: "no-unused-vars" extend ignored files section for
svelte and astro files (#18304) (Sysix)
- 3af4a88 linter: Add "Examples" headers to rules missing them (#18266)
(connorshea)
# Oxfmt
### 💥 BREAKING CHANGES

- 777fc40 ast: [**BREAKING**] Add `Ident` type (#18354) (Boshen)

### 🚀 Features

- d71c15d oxfmt: Enable tailwind sort inside xxx-in-js (#18417)
(leaysgur)
- 52b5003 formatter,oxfmt: Support Angular `@Component({ template,
styles })` (#18324) (leaysgur)

### 🐛 Bug Fixes

- 224140c oxfmt: Canonicalize `..` component in config path (#18570)
(leaysgur)
- 30b467e formatter: Preserve trailing comments before the semicolon in
class methods without a body (#18446) (Dunqing)
- c205b0d ast: Remove `ThisExpression` from `TSModuleReference` (#18489)
(Boshen)
- 164bbd7 formatter: Preserve trailing comments inside ternary alternate
branch (#18433) (Dunqing)
- 1c50800 formatter: Use HTML entity escaping for JSX attribute strings
(#18385) (Boshen)
- 4e156d2 formatter: Preserve parentheses for `in` expressions in arrow
function block bodies (#18352) (Boshen)
- 7e6c15b oxfmt: Increase Tailwind CSS test timeout for Windows CI
(#18339) (Boshen)
- 29966eb formatter/dead-code-removal: Handle tailwind sorting (#18321)
(leaysgur)
- 29f41be formatter: Only expand mapped types when newline immediately
follows opening brace (#18087) (Boshen)
- 2194552 formatter: Relocate leading comments for single-element
union/intersection types (#18083) (Boshen)

### ⚡ Performance

- 85ab400 formatter: Store `AstNodes` itself instead of `&'a AstNodes`
as the `parent` field of `AstNode` (#18428) (Dunqing)
- 194d384 formatter: Reduce AstNode size by 8 bytes using
following_span_start (#18347) (Dunqing)
- b2df8fb oxfmt: Enable tailwind plugin only for relevant parser
(#18418) (leaysgur)

### 📚 Documentation

- 8ccd853 npm: Update package homepage URLs and add keywords (#18509)
(Boshen)

Co-authored-by: Boshen <[email protected]>
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