feat(js_analyze): implement noJsxLeakedSemicolon by Netail · Pull Request #9912 · biomejs/biome

Netail · 2026-04-11T00:33:13Z

Summary

Port https://www.eslint-react.xyz/docs/rules/jsx-no-leaked-semicolon, which disallows leaked semicolons in JSX text nodes.

Partially generated by co-pilot

Test Plan

Unit tests

Docs

changeset-bot · 2026-04-11T00:33:21Z

🦋 Changeset detected

Latest commit: cb1cd6e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

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Netail · 2026-04-11T00:34:12Z

Unsure if this is also a common problem in svelte, astro or vue, else we can remove the JSX prefix

coderabbitai · 2026-04-11T00:41:21Z

Walkthrough

Adds a new nursery lint rule noJsxLeakedSemicolon that detects leading semicolons leaked into JsxText nodes when the text begins with ";\n" or ";\r". The rule emits a warning diagnostic and supplies an Unsafe automatic fix that removes the leading semicolon by replacing the JSX text token. Also adds an empty NoJsxLeakedSemicolonOptions type and module export, a changeset entry for @biomejs/biome, and test fixtures covering valid and invalid JSX cases.

Suggested reviewers

dyc3
ematipico

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: implementation of a new JSX linting rule, noJsxLeakedSemicolon, which aligns perfectly with the changeset.
Description check	✅ Passed	The description directly relates to the changeset by explaining the rule being ported from ESLint React and mentions unit tests as the test plan.

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codspeed-hq · 2026-04-11T00:50:59Z

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 196 skipped benchmarks¹

_{Comparing Netail:feat/no-jsx-leaked-semicolon (cb1cd6e) with main (19ff706)}

196 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. ↩

dyc3 · 2026-04-11T03:16:52Z

+        )
+    }
+
+    fn action(ctx: &RuleContext<Self>, _state: &Self::State) -> Option<JsRuleAction> {


should we even bother providing a fix for this? does the source rule?

Yes, the seem to provide a fix

https://github.com/Rel1cx/eslint-react/blob/stable/packages/plugins/eslint-plugin-react-jsx/src/rules/no-leaked-semicolon/no-leaked-semicolon.ts#L53-L55

dyc3 · 2026-04-11T03:20:23Z

Also the concern this rule covers is pretty much only a jsx problem, because of the nature of jsx. Not a problem in HTML and HTML-ish langs.

ematipico

Thank you! I believe the rule requires a bit more care:

all unsafe fixes are incorrect, check the snapshots. Did you check them?
I believe the configuration that triggers the rule is too naive. I believe the following case triggers the rule

<>
  <br />;

Some Tex 
</>

ematipico · 2026-04-11T05:17:49Z

+use biome_rule_options::no_jsx_leaked_semicolon::NoJsxLeakedSemicolonOptions;
+
+declare_lint_rule! {
+    /// Disallows leaked semicolons in JSX text nodes.


"Leaked" doesn't mean anything without context.

Here's a suggestion

"Flags semicolons that could be rendered as content inside JSX tags."

What about "Flags text nodes with a leading ; after a JSX element"?

You used "text nodes" which something related to parsing. See if you can find a plain language, beginner friendly

Netail · 2026-04-11T23:32:08Z

Thank you! I believe the rule requires a bit more care:

all unsafe fixes are incorrect, check the snapshots. Did you check them?

I believe the configuration that triggers the rule is too naive. I believe the following case triggers the rule
<>
  <br />;

Some Tex 
</>

They seem correct to me, the delete is under the ; 🤔
And the case you mentioned is correct to be flagged, why wouldn't it?

Am I overlooking something?

coderabbitai

Actionable comments posted: 1

🧹 Nitpick comments (1)

.changeset/ten-walls-throw.md (1)
6-6: Tiny copy polish (optional).

You could tighten this to: “This is often accidental and renders ; as text in the output.”

As per coding guidelines: “Write changeset descriptions concisely and clearly (1-3 sentences) …”
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In @.changeset/ten-walls-throw.md at line 6, Replace the current sentence "This
could be an unintentional mistake, resulting in a ';' being rendered as text in
the output." with the tighter phrasing "This is often accidental and renders `;`
as text in the output." in the changeset description—use backticks around the
semicolon to ensure it's rendered as inline code and keep the changeset
description concise (1–3 sentences).

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/biome_js_analyze/src/lint/nursery/no_jsx_leaked_semicolon.rs`:
- Around line 112-113: The matcher currently only detects text nodes that start
with ";\n" or ";\r", missing lone ";" or ";" followed directly by EOF/closing
tag; update the condition so it also treats a text of exactly ";" or any text
that starts with ";" (e.g., text == ";" || text.starts_with(';')) as a leaked
semicolon and return None accordingly; apply the same fix to the analogous check
later in the file (the second occurrence around the other matcher) so both
locations handle lone semicolons and semicolons without a newline.

---

Nitpick comments:
In @.changeset/ten-walls-throw.md:
- Line 6: Replace the current sentence "This could be an unintentional mistake,
resulting in a ';' being rendered as text in the output." with the tighter
phrasing "This is often accidental and renders `;` as text in the output." in
the changeset description—use backticks around the semicolon to ensure it's
rendered as inline code and keep the changeset description concise (1–3
sentences).

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Push a commit to this branch (recommended)
Create a new PR with the fixes

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Reviewing files that changed from the base of the PR and between 20bf6b5 and cb1cd6e.

⛔ Files ignored due to path filters (6)

crates/biome_cli/src/execute/migrate/eslint_any_rule_to_biome.rs is excluded by !**/migrate/eslint_any_rule_to_biome.rs and included by **
crates/biome_configuration/src/analyzer/linter/rules.rs is excluded by !**/rules.rs and included by **
crates/biome_configuration/src/generated/domain_selector.rs is excluded by !**/generated/**, !**/generated/** and included by **
crates/biome_configuration/src/generated/linter_options_check.rs is excluded by !**/generated/**, !**/generated/** and included by **
crates/biome_diagnostics_categories/src/categories.rs is excluded by !**/categories.rs and included by **
crates/biome_js_analyze/tests/specs/nursery/noJsxLeakedSemicolon/invalid.jsx.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (2)

.changeset/ten-walls-throw.md
crates/biome_js_analyze/src/lint/nursery/no_jsx_leaked_semicolon.rs

coderabbitai · 2026-04-11T23:37:02Z

+        if !(text.starts_with(";\n") || text.starts_with(";\r")) {
+            return None;


⚠️ Potential issue | 🟠 Major

Leaked ; without newline is currently missed.

The matcher only catches ";\n" / ";\r", so a lone ";" text node (for example inline before a closing tag) is not reported and not fixed.

Proposed patch

- if !(text.starts_with(";\n") || text.starts_with(";\r")) { + if !text.starts_with(';') { + return None; + } + let rest = &text[1..]; + if !(rest.is_empty() || rest.starts_with('\n') || rest.starts_with('\r')) { return None; } @@ - // Remove the leading `;` - let new_text = text[1..].to_string(); + let new_text = text.strip_prefix(';')?.to_string();

Also applies to: 142-143

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@crates/biome_js_analyze/src/lint/nursery/no_jsx_leaked_semicolon.rs` around lines 112 - 113, The matcher currently only detects text nodes that start with ";\n" or ";\r", missing lone ";" or ";" followed directly by EOF/closing tag; update the condition so it also treats a text of exactly ";" or any text that starts with ";" (e.g., text == ";" || text.starts_with(';')) as a leaked semicolon and return None accordingly; apply the same fix to the analogous check later in the file (the second occurrence around the other matcher) so both locations handle lone semicolons and semicolons without a newline.

Netail · 2026-04-11T23:43:06Z

I just realized this is pretty much noSuspiciousSemicolonInJsx 🤦‍♂️, however name-wise & implementation I think this one is better perhaps? (noJSX... seems bit more up to the frameworks specific rule standard + there's a quick fix) 🤔

ematipico · 2026-04-12T07:47:13Z

Thank you! I believe the rule requires a bit more care:

all unsafe fixes are incorrect, check the snapshots. Did you check them?

I believe the configuration that triggers the rule is too naive. I believe the following case triggers the rule
<>
  <br />;

Some Tex 
</>
They seem correct to me, the delete is under the ; 🤔
And the case you mentioned is correct to be flagged, why wouldn't it?

Am I overlooking something?

Sorry, my bad. The rule should flag that example, but it doesn't. Or it does, but there aren't any tests. I believe it doesn't, in fact code rabbit says the same

github-actions bot added A-Linter Area: linter L-JavaScript Language: JavaScript and super languages A-Diagnostic Area: diagnostocis labels Apr 11, 2026

Netail marked this pull request as draft April 11, 2026 00:42

github-actions bot added A-CLI Area: CLI A-Project Area: project labels Apr 11, 2026

feat(js_analyze): implement noJsxLeakedSemicolon

20bf6b5

Netail force-pushed the feat/no-jsx-leaked-semicolon branch from 500ad01 to 20bf6b5 Compare April 11, 2026 00:59

Netail marked this pull request as ready for review April 11, 2026 01:23

dyc3 reviewed Apr 11, 2026

View reviewed changes

ematipico requested changes Apr 11, 2026

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Merge branch 'main' into feat/no-jsx-leaked-semicolon

f6200ec

Netail force-pushed the feat/no-jsx-leaked-semicolon branch from 1497522 to e93576e Compare April 11, 2026 23:29

fix: feedback

cb1cd6e

Netail force-pushed the feat/no-jsx-leaked-semicolon branch from e93576e to cb1cd6e Compare April 11, 2026 23:29

Netail requested review from dyc3 and ematipico April 11, 2026 23:30

coderabbitai bot reviewed Apr 11, 2026

View reviewed changes

		if !(text.starts_with(";\n") \|\| text.starts_with(";\r")) {
		return None;

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