--- name: biome-linting-c0069b6dd8a4 user-invocable: false description: Use when applying Biome's linting capabilities, rule categories, and code quality enforcement to JavaScript/TypeScript projects. allowed-tools: [Read, Write, Edit, Bash, Glob, Grep] --- # Biome Linting Expert knowledge of Biome's linting capabilities, rule categories, and code quality enforcement for JavaScript and TypeScript projects. ## Overview Biome's linter provides fast, comprehensive code quality checks with a focus on correctness, performance, security, and best practices. It's designed to catch common bugs and enforce consistent code patterns. ## Core Commands ### Basic Linting ```bash # Check files without fixing biome check . # Check and auto-fix biome check --write . # Check specific files biome check src/**/*.ts # CI mode (strict, fails on warnings) biome ci . ``` ### Command Options ```bash # Verbose output biome check --verbose . # JSON output biome check --json . # Only lint (skip formatting) biome lint . # Apply safe fixes only biome check --write --unsafe=false . ``` ## Rule Categories ### Accessibility (a11y) Rules for web accessibility and WCAG compliance: ```json { "linter": { "rules": { "a11y": { "recommended": true, "noAccessKey": "error", "noAriaHiddenOnFocusable": "error", "noAutofocus": "warn", "noBlankTarget": "error", "noPositiveTabindex": "error", "useAltText": "error", "useAnchorContent": "error", "useButtonType": "error", "useValidAriaProps": "error" } } } } ``` Common violations: - Missing alt text on images - Autofocus on form elements - Positive tabindex values - Links without content - Invalid ARIA properties ### Complexity Rules to reduce code complexity: ```json { "linter": { "rules": { "complexity": { "recommended": true, "noBannedTypes": "error", "noExcessiveCognitiveComplexity": "warn", "noExtraBooleanCast": "error", "noMultipleSpacesInRegularExpressionLiterals": "error", "noUselessCatch": "error", "noUselessConstructor": "error", "noUselessEmptyExport": "error", "noUselessFragments": "error", "noUselessLabel": "error", "noUselessRename": "error", "noUselessSwitchCase": "error", "noWith": "error" } } } } ``` ### Correctness Rules for code correctness and bug prevention: ```json { "linter": { "rules": { "correctness": { "recommended": true, "noChildrenProp": "error", "noConstAssign": "error", "noConstantCondition": "error", "noConstructorReturn": "error", "noEmptyPattern": "error", "noGlobalObjectCalls": "error", "noInnerDeclarations": "error", "noInvalidConstructorSuper": "error", "noNewSymbol": "error", "noNonoctalDecimalEscape": "error", "noPrecisionLoss": "error", "noSelfAssign": "error", "noSetterReturn": "error", "noSwitchDeclarations": "error", "noUndeclaredVariables": "error", "noUnreachable": "error", "noUnreachableSuper": "error", "noUnsafeFinally": "error", "noUnsafeOptionalChaining": "error", "noUnusedLabels": "error", "noUnusedVariables": "error", "useIsNan": "error", "useValidForDirection": "error", "useYield": "error" } } } } ``` Critical rules: - `noUndeclaredVariables`: Catch undeclared variables - `noUnusedVariables`: Remove unused code - `noConstAssign`: Prevent const reassignment - `noUnreachable`: Detect unreachable code - `useIsNan`: Use isNaN() for NaN checks ### Performance Rules for performance optimization: ```json { "linter": { "rules": { "performance": { "recommended": true, "noAccumulatingSpread": "warn", "noDelete": "error" } } } } ``` ### Security Rules for security best practices: ```json { "linter": { "rules": { "security": { "recommended": true, "noDangerouslySetInnerHtml": "error", "noDangerouslySetInnerHtmlWithChildren": "error", "noGlobalEval": "error" } } } } ``` Critical security rules: - Prevent XSS via innerHTML - Block eval() usage - Detect security vulnerabilities ### Style Code style and consistency rules: ```json { "linter": { "rules": { "style": { "recommended": true, "noArguments": "error", "noCommaOperator": "error", "noImplicitBoolean": "warn", "noNegationElse": "warn", "noNonNullAssertion": "warn", "noParameterAssign": "error", "noRestrictedGlobals": "error", "noShoutyConstants": "warn", "noUnusedTemplateLiteral": "error", "noVar": "error", "useBlockStatements": "warn", "useCollapsedElseIf": "warn", "useConst": "error", "useDefaultParameterLast": "error", "useEnumInitializers": "warn", "useExponentiationOperator": "error", "useFragmentSyntax": "error", "useNumericLiterals": "error", "useSelfClosingElements": "error", "useShorthandArrayType": "error", "useSingleVarDeclarator": "error", "useTemplate": "warn", "useWhile": "error" } } } } ``` Key style rules: - `noVar`: Use let/const instead of var - `useConst`: Prefer const for immutable bindings - `noNonNullAssertion`: Avoid ! assertions in TypeScript - `useTemplate`: Prefer template literals ### Suspicious Rules for suspicious code patterns: ```json { "linter": { "rules": { "suspicious": { "recommended": true, "noArrayIndexKey": "warn", "noAssignInExpressions": "error", "noAsyncPromiseExecutor": "error", "noCatchAssign": "error", "noClassAssign": "error", "noCommentText": "error", "noCompareNegZero": "error", "noConsoleLog": "warn", "noControlCharactersInRegex": "error", "noDebugger": "error", "noDoubleEquals": "error", "noDuplicateCase": "error", "noDuplicateClassMembers": "error", "noDuplicateObjectKeys": "error", "noDuplicateParameters": "error", "noEmptyBlockStatements": "warn", "noExplicitAny": "warn", "noExtraNonNullAssertion": "error", "noFallthroughSwitchClause": "error", "noFunctionAssign": "error", "noGlobalAssign": "error", "noImportAssign": "error", "noLabelVar": "error", "noMisleadingCharacterClass": "error", "noPrototypeBuiltins": "error", "noRedeclare": "error", "noSelfCompare": "error", "noShadowRestrictedNames": "error", "noUnsafeNegation": "error", "useDefaultSwitchClauseLast": "error", "useGetterReturn": "error", "useValidTypeof": "error" } } } } ``` Critical suspicious patterns: - `noExplicitAny`: Avoid any in TypeScript - `noConsoleLog`: Remove console.log in production - `noDebugger`: Remove debugger statements - `noDoubleEquals`: Use === instead of == - `noDuplicateObjectKeys`: Catch duplicate keys ## Rule Configuration Patterns ### Strict Configuration Maximum strictness for high-quality codebases: ```json { "linter": { "enabled": true, "rules": { "recommended": true, "a11y": { "recommended": true }, "complexity": { "recommended": true }, "correctness": { "recommended": true }, "performance": { "recommended": true }, "security": { "recommended": true }, "style": { "recommended": true }, "suspicious": { "recommended": true, "noExplicitAny": "error", "noConsoleLog": "error" } } } } ``` ### Gradual Adoption Start lenient and progressively tighten: ```json { "linter": { "enabled": true, "rules": { "recommended": true, "suspicious": { "noExplicitAny": "warn", "noConsoleLog": "warn" }, "style": { "noVar": "error", "useConst": "warn" } } } } ``` ### Framework-Specific React configuration example: ```json { "linter": { "rules": { "recommended": true, "a11y": { "recommended": true }, "correctness": { "recommended": true, "noChildrenProp": "error" }, "security": { "noDangerouslySetInnerHtml": "error" }, "suspicious": { "noArrayIndexKey": "error" } } } } ``` ## Ignoring Violations ### Inline Comments Suppress specific violations: ```javascript // biome-ignore lint/suspicious/noExplicitAny: Legacy code function legacyFunction(data: any) { return data; } // biome-ignore lint/suspicious/noConsoleLog: Debug logging console.log('Debug info'); // Multiple rules // biome-ignore lint/suspicious/noExplicitAny lint/style/useConst: Migration var config: any = {}; ``` ### File-Level Ignores Ignore entire file: ```javascript /* biome-ignore-file */ // Legacy file, skip all linting ``` ### Configuration Ignores Ignore patterns in biome.json: ```json { "files": { "ignore": [ "**/generated/**", "**/*.config.js", "**/vendor/**" ] } } ``` ## Best Practices 1. **Enable Recommended Rules** - Start with `"recommended": true` 2. **Progressive Enhancement** - Add stricter rules gradually 3. **Document Exceptions** - Explain why rules are disabled 4. **Use Inline Ignores Sparingly** - Prefer fixing over ignoring 5. **Security First** - Never disable security rules 6. **CI Enforcement** - Use `biome ci` in pipelines 7. **Pre-commit Hooks** - Catch issues before commit 8. **Team Agreement** - Discuss rule changes with team 9. **Regular Review** - Periodically review disabled rules 10. **Fix Warnings** - Don't let warnings accumulate ## Common Pitfalls 1. **Ignoring Errors** - Using biome-ignore instead of fixing 2. **Disabling Security** - Turning off security rules 3. **No CI Check** - Not enforcing in continuous integration 4. **Too Lenient** - Setting everything to "warn" 5. **No Documentation** - Not explaining disabled rules 6. **Inconsistent Config** - Different rules per package 7. **Ignoring Warnings** - Treating warnings as optional 8. **Wrong Rule Names** - Typos in rule configuration 9. **Overly Strict** - Blocking team productivity 10. **No Migration Plan** - Enabling all rules at once ## Advanced Topics ### Custom Rule Sets Create shared rule sets for organization: ```json { "extends": ["@company/biome-config"], "linter": { "rules": { "suspicious": { "noConsoleLog": "error" } } } } ``` ### Per-Directory Rules Use overrides for different code areas: ```json { "overrides": [ { "include": ["src/**/*.ts"], "linter": { "rules": { "suspicious": { "noExplicitAny": "error" } } } }, { "include": ["scripts/**/*.js"], "linter": { "rules": { "suspicious": { "noConsoleLog": "off" } } } } ] } ``` ### Migration Strategy Migrating from ESLint: 1. **Install Biome**: `npm install -D @biomejs/biome` 2. **Initialize**: `npx biome init` 3. **Run Check**: `npx biome check .` to see violations 4. **Fix Automatically**: `npx biome check --write .` 5. **Address Remaining**: Fix issues that can't auto-fix 6. **Tune Rules**: Adjust rules based on team needs 7. **Update CI**: Replace ESLint with Biome 8. **Remove ESLint**: After validation period ## Integration Patterns ### Package.json Scripts ```json { "scripts": { "lint": "biome check .", "lint:fix": "biome check --write .", "lint:ci": "biome ci ." } } ``` ### Pre-commit Hook Using husky: ```json { "husky": { "hooks": { "pre-commit": "biome check --write --changed" } } } ``` ### GitHub Actions ```yaml - name: Run Biome run: npx biome ci . ``` ## Troubleshooting ### False Positives If rule triggers incorrectly: 1. Verify rule is appropriate for your code 2. Check if bug in Biome (report upstream) 3. Use biome-ignore with explanation 4. Consider disabling rule if widespread ### Performance Issues If linting is slow: 1. Update to latest Biome version 2. Use VCS integration 3. Ignore large generated directories 4. Check for file pattern issues ### Rules Not Applied Verify: 1. Linter is enabled in config 2. Rule category is enabled 3. Rule name is spelled correctly 4. No overrides disabling it 5. Files are not ignored ## When to Use This Skill - Setting up linting for new projects - Migrating from ESLint to Biome - Configuring rule sets for teams - Troubleshooting linting errors - Optimizing code quality checks - Establishing code standards - Training team on Biome linting - Integrating linting into CI/CD --- Source attribution: TheBushidoCollective Original project: https://github.com/TheBushidoCollective/han/blob/19caa51d5fd144ef6b2764f2332f4c856aa5d1af/plugins/validation/biome/skills/biome-linting/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice # Functional Source License, Version 1.1, ALv2 Future License ## Abbreviation FSL-1.1-ALv2 ## Notice Copyright 2025 The Bushido Collective ## Terms and Conditions ### Licensor ("We") The party offering the Software under these Terms and Conditions. ### The Software The "Software" is each version of the software that we make available under these Terms and Conditions, as indicated by our inclusion of these Terms and Conditions with the Software. ### License Grant Subject to your compliance with this License Grant and the Patents, Redistribution and Trademark clauses below, we hereby grant you the right to use, copy, modify, create derivative works, publicly perform, publicly display and redistribute the Software for any Permitted Purpose identified below. ### Permitted Purpose A Permitted Purpose is any purpose other than a Competing Use. 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If you make a claim against any party that the Software infringes or contributes to the infringement of any patent, then your patent license to the Software ends immediately. ### Redistribution The Terms and Conditions apply to all copies, modifications and derivatives of the Software. If you redistribute any copies, modifications or derivatives of the Software, you must include a copy of or a link to these Terms and Conditions and not remove any copyright notices provided in or with the Software. ### Disclaimer THE SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, TITLE OR NON-INFRINGEMENT. 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You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: TheBushidoCollective Original project: https://github.com/TheBushidoCollective/han/blob/19caa51d5fd144ef6b2764f2332f4c856aa5d1af/plugins/validation/biome/skills/biome-linting/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering Roles: Backend Developer, DevOps / SRE, Frontend Developer, Full-Stack Developer, QA / Test Engineer Specialties: Testing Tools: Biome Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: 5b768f42962862597acc57781906ca15808fff271320de5275cab6a57a443150