Replace ESLint with Biome for PR CI checks

.github/workflows/ci.yaml

@@ -19,8 +19,11 @@ jobs:
 
       - run: pnpm install --frozen-lockfile
 
-      - run: pnpm run lint
+      - name: Biome check
+        run: pnpm run lint
 
-      - run: pnpm run typecheck
+      - name: TypeScript typecheck
+        run: pnpm run typecheck
 
-      - run: pnpm run test
+      - name: Tests
+        run: pnpm run test

.grit/no-iife.grit

@@ -0,0 +1,25 @@
+engine biome(2.0)
+language js(typescript, jsx)
+
+or {
+  // Match: (function() { ... })() or (function(args) { ... })()
+  `($func)()` as $match where {
+    $func <: or {
+      `function() { $body }`,
+      `function($args) { $body }`,
+      `async function() { $body }`,
+      `async function($args) { $body }`
+    },
+    register_diagnostic(span=$match, message="Avoid using IIFEs. Consider extracting to a helper function.", severity="error")
+  },
+  // Match: (() => { ... })() or ((args) => { ... })()
+  `($arrow)()` as $match where {
+    $arrow <: or {
+      `() => $body`,
+      `($args) => $body`,
+      `async () => $body`,
+      `async ($args) => $body`
+    },
+    register_diagnostic(span=$match, message="Avoid using IIFEs. Consider extracting to a helper function.", severity="error")
+  }
+}

.grit/prefer-nullish-over-optional-nullable.grit

@@ -0,0 +1,24 @@
+// Pattern: Detect .optional().nullable() or .nullable().optional() on zod schemas
+// These should be replaced with .nullish() for better clarity and correctness
+// Matches both direct chains and chains with other method calls in between
+// Only matches expressions that start with z. to ensure we're targeting zod schemas
+
+engine biome(2.0)
+language js(typescript, jsx)
+
+or {
+  // Direct chains starting from a zod constructor
+  `z.$fn($...).nullable().optional()` as $match where {
+    register_diagnostic(span=$match, message="Use .nullish() instead of .nullable().optional(). The .nullish() method is equivalent and more concise.", severity="error")
+  },
+  `z.$fn($...).optional().nullable()` as $match where {
+    register_diagnostic(span=$match, message="Use .nullish() instead of .optional().nullable(). The .nullish() method is equivalent and more concise.", severity="error")
+  },
+  // Allow one method in between (covers common cases like .default(), .array(), .openapi(), etc.)
+  `z.$fn($...).$mid.nullable().optional()` as $match where {
+    register_diagnostic(span=$match, message="Use .nullish() instead of .nullable().optional() with extra chaining. The .nullish() method is equivalent and more concise.", severity="error")
+  },
+  `z.$fn($...).$mid.optional().nullable()` as $match where {
+    register_diagnostic(span=$match, message="Use .nullish() instead of .optional().nullable() with extra chaining. The .nullish() method is equivalent and more concise.", severity="error")
+  }
+}

.grit/use-named-arguments.grit

@@ -0,0 +1,45 @@
+engine biome(2.0)
+language js(typescript, jsx)
+
+or {
+  // Function declarations
+  `function $name($a, $b, $c, $d, $...) { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Function declarations with return type
+  `function $name($a, $b, $c, $d, $...): $ret { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Async function declarations
+  `async function $name($a, $b, $c, $d, $...) { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Async function declarations with return type
+  `async function $name($a, $b, $c, $d, $...): $ret { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Function expressions
+  `function($a, $b, $c, $d, $...) { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Function expressions with return type
+  `function($a, $b, $c, $d, $...): $ret { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Async function expressions
+  `async function($a, $b, $c, $d, $...) { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Async function expressions with return type
+  `async function($a, $b, $c, $d, $...): $ret { $body }` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Arrow functions
+  `($a, $b, $c, $d, $...) => $body` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  },
+  // Arrow functions with return type
+  `($a, $b, $c, $d, $...): $ret => $body` as $match where {
+    register_diagnostic(span=$match, message="Functions with more than 3 parameters should use named arguments with object destructuring", severity="error")
+  }
+}

biome.json

@@ -0,0 +1,136 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.4.8/schema.json",
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true,
+    "defaultBranch": "origin/main"
+  },
+  "plugins": [
+    ".grit/no-iife.grit",
+    ".grit/use-named-arguments.grit",
+    ".grit/prefer-nullish-over-optional-nullable.grit"
+  ],
+  "files": {
+    "ignoreUnknown": false,
+    "includes": [
+      "**",
+      "!**/*.json",
+      "!!**/biome.json",
+      "!esm/**"
+    ]
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineWidth": 100,
+    "expand": "always",
+    "attributePosition": "multiline"
+  },
+  "assist": {
+    "actions": {
+      "source": {
+        "organizeImports": {
+          "level": "on"
+        }
+      }
+    }
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true,
+      "complexity": {
+        "useLiteralKeys": "off",
+        "noExtraBooleanCast": "off",
+        "noForEach": "off",
+        "noBannedTypes": "error",
+        "noUselessSwitchCase": "off"
+      },
+      "style": {
+        "noNonNullAssertion": "off",
+        "useNodejsImportProtocol": "error",
+        "useTemplate": "off",
+        "useBlockStatements": "error",
+        "noParameterAssign": "error",
+        "useConst": "error",
+        "useAsConstAssertion": "error",
+        "useDefaultParameterLast": "error",
+        "useEnumInitializers": "error",
+        "useSelfClosingElements": "error",
+        "useSingleVarDeclarator": "error",
+        "noUnusedTemplateLiteral": "error",
+        "useNumberNamespace": "error",
+        "noInferrableTypes": "error",
+        "noUselessElse": "error",
+        "useImportType": {
+          "level": "on",
+          "options": {
+            "style": "separatedType"
+          }
+        }
+      },
+      "correctness": {
+        "noUnusedImports": "error",
+        "useExhaustiveDependencies": "off",
+        "noInnerDeclarations": "error",
+        "useParseIntRadix": "error"
+      },
+      "suspicious": {
+        "noExplicitAny": "off",
+        "noAssignInExpressions": "error",
+        "noAsyncPromiseExecutor": "off",
+        "noFallthroughSwitchClause": "error",
+        "noConsole": "off",
+        "noDoubleEquals": {
+          "level": "error",
+          "options": {
+            "ignoreNull": false
+          }
+        },
+        "noExtraNonNullAssertion": "error"
+      },
+      "performance": {
+        "recommended": true,
+        "noAccumulatingSpread": "error"
+      },
+      "security": {
+        "recommended": true
+      }
+    }
+  },
+  "javascript": {
+    "formatter": {
+      "expand": "always",
+      "lineWidth": 100,
+      "arrowParentheses": "always",
+      "quoteProperties": "asNeeded",
+      "trailingCommas": "all",
+      "semicolons": "always",
+      "bracketSpacing": true,
+      "bracketSameLine": false,
+      "quoteStyle": "single",
+      "enabled": true
+    }
+  },
+  "overrides": [
+    {
+      "includes": [
+        "tests/**",
+        "**/*.test.ts",
+        "**/*.spec.ts"
+      ],
+      "linter": {
+        "rules": {
+          "suspicious": {
+            "noExplicitAny": "off"
+          },
+          "correctness": {
+            "useYield": "off"
+          }
+        }
+      }
+    }
+  ]
+}

package.json

@@ -103,7 +103,8 @@
     "LICENSE"
   ],
   "scripts": {
-    "lint": "eslint --cache --max-warnings=0 src",
+    "lint": "biome check src tests",
+    "lint:fix": "biome check --write src tests",
     "build": "tsc",
     "test": "vitest --run --project unit",
     "test:e2e": "vitest --run --project e2e",
@@ -117,15 +118,12 @@
     "zod": "^4.0.0"
   },
   "devDependencies": {
+    "@biomejs/biome": "^2.4.10",
     "@changesets/changelog-github": "^0.6.0",
     "@changesets/cli": "^2.30.0",
-    "@eslint/js": "^9.19.0",
     "@types/node": "^22.13.12",
     "dotenv": "^16.4.7",
-    "eslint": "^9.19.0",
-    "globals": "^15.14.0",
     "typescript": "~5.8.3",
-    "typescript-eslint": "^8.26.0",
     "vitest": "^3.2.4"
   },
   "pnpm": {