feat(lint/nursery): new rule - noInvertedTernary by js2me · Pull Request #9312 · biomejs/biome

js2me · 2026-03-03T14:55:19Z

This PR was written primarily by GPT-5.3 Codex

Summary

Added a new nursery lint rule: noInvertedTernary.

The rule reports inverted ternary conditions such as A !== B ? C : D (and A != B ? C : D) and provides an auto-fix that rewrites them to the direct form: A === B ? D : C (or A == B ? D : C).
This improves readability by avoiding negated ternary tests.

Also added rule tests (valid / invalid) and updated snapshots.

Test Plan

Ran:
- cargo test -p biome_js_analyze no_inverted_ternary -- --nocapture
- INSTA_UPDATE=always cargo test -p biome_js_analyze no_inverted_ternary
Verified:
- diagnostics are reported for inverted ternaries
- safe auto-fix rewrites them to the direct form
- snapshots were updated accordingly

Docs

Added rustdoc documentation and examples in the rule implementation (invalid and valid cases).
No separate website documentation PR was needed for this change.

This PR was created with AI assistance (Cursor AI assistant).

changeset-bot · 2026-03-03T14:55:36Z

🦋 Changeset detected

Latest commit: 646c8e9

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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coderabbitai · 2026-03-03T15:04:34Z

No actionable comments were generated in the recent review. 🎉

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📒 Files selected for processing (2)

.changeset/cuddly-cougars-hope.md
crates/biome_js_analyze/src/lint/nursery/no_inverted_ternary.rs

Walkthrough

Adds a new ESLint-style lint rule noInvertedTernary to the biome JS analysis crate that detects ternary expressions using inequality tests with flipped branches and provides a safe automatic fix that flips the operator and swaps branches. Includes rule declaration, diagnostics, fix implementation, options type and export, tests (valid/invalid), and minor message ownership fixes in two existing diagnostics.

Suggested labels

A-Project

Suggested reviewers

ematipico
dyc3

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a new nursery lint rule named noInvertedTernary.
Description check	✅ Passed	The description is well-related to the changeset, detailing the new rule, its purpose, test coverage, and verification steps performed.

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coderabbitai

Actionable comments posted: 2

🧹 Nitpick comments (1)

crates/biome_rule_options/src/no_inverted_ternary.rs (1)
3-6: Add a short rustdoc block for the options type.

The struct is correct; it just needs inline docs to match repository convention for rule options.
📝 Suggested patch
+/// Options for `noInvertedTernary`.
+///
+/// This rule currently has no configurable options.
 pub struct NoInvertedTernaryOptions {}
As per coding guidelines: "Use inline rustdoc documentation for rules, assists, and their options".
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@crates/biome_rule_options/src/no_inverted_ternary.rs` around lines 3 - 6, Add
an inline rustdoc comment above the NoInvertedTernaryOptions struct describing
what this options type controls (e.g., options for the "no inverted ternary"
lint/rule), include a short one-line summary and, if applicable, list any fields
or default behavior; place the doc comment (/// ...) directly above pub struct
NoInvertedTernaryOptions {} to match repository convention for rule options.

🤖 Prompt for all review comments with AI agents

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

Inline comments:
In @.changeset/cuddly-cougars-hope.md:
- Line 5: Update the changeset note for the new rule "noInvertedTernary" to be
user-facing: describe in one sentence what patterns the rule catches (e.g.,
ternary expressions with inverted condition/result order that reduce
readability), explain the intended fix, and include one inline invalid example
such as `const x = condition ? falseValue : trueValue;` (or a short code block)
showing the problematic inverted ternary; ensure the changeset text is clear for
end users and replaces the minimal "new rule noInvertedTernary" line with this
expanded description.

In `@crates/biome_js_analyze/src/lint/nursery/no_inverted_ternary.rs`:
- Around line 56-57: The current code casts node.test() directly to a
JsBinaryExpression (via test_expression.as_js_binary_expression()), which fails
for parenthesised tests like `(a !== b) ? c : d`; update both run() and action()
to unwrap parenthesised expressions first by calling .inner_expression() on the
test_expression before attempting .as_js_binary_expression(), and do the same
for the similar usage around the other occurrence (the test variable at lines
83-84) so parenthesised binary tests are correctly detected and handled.

---

Nitpick comments:
In `@crates/biome_rule_options/src/no_inverted_ternary.rs`:
- Around line 3-6: Add an inline rustdoc comment above the
NoInvertedTernaryOptions struct describing what this options type controls
(e.g., options for the "no inverted ternary" lint/rule), include a short
one-line summary and, if applicable, list any fields or default behavior; place
the doc comment (/// ...) directly above pub struct NoInvertedTernaryOptions {}
to match repository convention for rule options.

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⛔ Files ignored due to path filters (3)

crates/biome_diagnostics_categories/src/categories.rs is excluded by !**/categories.rs and included by **
crates/biome_js_analyze/tests/specs/nursery/noInvertedTernary/invalid.js.snap is excluded by !**/*.snap and included by **
crates/biome_js_analyze/tests/specs/nursery/noInvertedTernary/valid.js.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (8)

.changeset/cuddly-cougars-hope.md
crates/biome_js_analyze/src/lint/correctness/use_exhaustive_dependencies.rs
crates/biome_js_analyze/src/lint/nursery/no_inverted_ternary.rs
crates/biome_js_analyze/tests/specs/nursery/noInvertedTernary/invalid.js
crates/biome_js_analyze/tests/specs/nursery/noInvertedTernary/valid.js
crates/biome_json_analyze/src/lint/nursery/use_required_scripts.rs
crates/biome_rule_options/src/lib.rs
crates/biome_rule_options/src/no_inverted_ternary.rs

coderabbitai · 2026-03-03T15:04:37Z

+"@biomejs/biome": patch
+---
+
+new rule noInvertedTernary


⚠️ Potential issue | 🟡 Minor

Please expand the changeset note for end users.

new rule noInvertedTernary is a bit too minimal for release notes; include what it catches and one invalid example.

✍️ Suggested rewrite

-new rule noInvertedTernary +Add the nursery rule `noInvertedTernary`, which flags inverted ternaries like +`a !== b ? x : y` and auto-fixes them to `a === b ? y : x`.

As per coding guidelines: "Create changeset files ... with ... end-user-focused descriptions". Based on learnings: "For new lint rules in changesets, show an example of invalid case in inline code or code block".

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

new rule noInvertedTernary

Add the nursery rule `noInvertedTernary`, which flags inverted ternaries like

`a !== b ? x : y` and auto-fixes them to `a === b ? y : x`.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In @.changeset/cuddly-cougars-hope.md at line 5, Update the changeset note for the new rule "noInvertedTernary" to be user-facing: describe in one sentence what patterns the rule catches (e.g., ternary expressions with inverted condition/result order that reduce readability), explain the intended fix, and include one inline invalid example such as `const x = condition ? falseValue : trueValue;` (or a short code block) showing the problematic inverted ternary; ensure the changeset text is clear for end users and replaces the minimal "new rule noInvertedTernary" line with this expanded description.

Netail

Seems very related to https://biomejs.dev/linter/rules/no-negation-else/, could be a feature in that rule. (Does already cover != & !== for if statements & full negative in ternaries)

Also some generated schema data is missing.

Netail · 2026-03-03T15:36:19Z

Unrelated to new rule

Netail · 2026-03-03T15:36:25Z

Unrelated to new rule

dyc3 · 2026-03-03T17:55:06Z

+    pub NoInvertedTernary {
+        version: "next",
+        name: "noInvertedTernary",
+        language: "js",
+        recommended: false,
+        fix_kind: FixKind::Safe,
+    }


Are there existing eslint rules that do this? If so, add them as rule sources

https://eslint.org/docs/latest/rules/no-negated-condition does, which we already "implemented" (https://biomejs.dev/linter/rules/no-negation-else/), but our implementation does not seem to cover this yet. Created #9351

dyc3 · 2026-03-03T17:56:57Z

+                },
+            )
+            .note(markup! {
+                "Use an equality check in the test and swap the two branches for better readability."


Follow the rule pillars. The messages must say:

What the error is (in diagnostic)

Why it is an error (in diagnostic)

How to fix the error (action message)

dyc3 · 2026-03-03T17:58:39Z

+
+        Some(JsRuleAction::new(
+            ctx.metadata().action_category(ctx.category(), ctx.group()),
+            Applicability::Always,


Suggested change

Applicability::Always,

ctx.metadata().applicability(),

dyc3 · 2026-03-03T18:00:55Z

+    /// ### Valid
+    ///
+    /// ```js
+    /// const value = i === data.depth - 1 ? 0 : 18;
+    /// ```
+    ///
+    /// ```js
+    /// const result = foo === bar ? second : first;
+    /// ```


nit: these valid cases can be combined

Netail · 2026-03-05T20:48:18Z

Will be covered by noNegationElse with #9351

js2me · 2026-03-05T21:09:49Z

Thank you, this thing is really useful

Сергей Волков added 2 commits March 3, 2026 17:49

feat(lint/nursery): new rule - noInvertedTernary

bc95cfb

chore: fix changeset

78ece89

github-actions Bot added A-Linter Area: linter L-JavaScript Language: JavaScript and super languages L-JSON Language: JSON and super languages A-Diagnostic Area: diagnostocis labels Mar 3, 2026

coderabbitai Bot reviewed Mar 3, 2026

View reviewed changes

Сергей Волков added 2 commits March 3, 2026 18:12

chore: apply comments at PR

b411393

chore: update changeset

646c8e9

Netail reviewed Mar 3, 2026

View reviewed changes

dyc3 requested changes Mar 3, 2026

View reviewed changes

Netail mentioned this pull request Mar 5, 2026

feat(js_analyze): noNegationElse support inequality & strict inequality operator #9351

Merged

Netail closed this Mar 5, 2026

	new rule noInvertedTernary
	Add the nursery rule `noInvertedTernary`, which flags inverted ternaries like
	`a !== b ? x : y` and auto-fixes them to `a === b ? y : x`.

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js2me commented Mar 3, 2026

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