perf(linter/plugins): store if rule is fixable as boolean

apps/oxlint/src-js/plugins/context.ts

@@ -1,7 +1,6 @@
 import { getFixes } from './fix.js';
 
 import type { Fix, FixFn } from './fix.ts';
-import type { RuleMeta } from './types.ts';
 
 // Diagnostic in form passed by user to `Context#report()`
 export interface Diagnostic {
@@ -70,8 +69,8 @@ export interface InternalContext {
   filePath: string;
   // Options
   options: unknown[];
-  // Rule metadata
-  meta: RuleMeta;
+  // `true` if rule can provide fixes (`meta.fixable` in `RuleMeta` is 'code' or 'whitespace')
+  isFixable: boolean;
 }
 
 /**
@@ -88,13 +87,13 @@ export class Context {
    * @class
    * @param fullRuleName - Rule name, in form `<plugin>/<rule>`
    */
-  constructor(fullRuleName: string, meta: RuleMeta) {
+  constructor(fullRuleName: string, isFixable: boolean) {
     this.#internal = {
       id: fullRuleName,
       filePath: '',
       ruleIndex: -1,
       options: [],
-      meta,
+      isFixable,
     };
   }
 

apps/oxlint/src-js/plugins/fix.ts

@@ -144,7 +144,7 @@ export function getFixes(diagnostic: Diagnostic, internal: InternalContext): Fix
 
   // ESLint does not throw this error if `fix` function returns only falsy values.
   // We've already exited if that is the case, so we're reproducing that behavior.
-  if (internal.meta.fixable === null) {
+  if (internal.isFixable === false) {
     throw new Error('Fixable rules must set the `meta.fixable` property to "code" or "whitespace".');
   }
 

apps/oxlint/src-js/plugins/load.ts

@@ -68,11 +68,6 @@ interface PluginDetails {
   ruleNames: string[];
 }
 
-// Default rule metadata, used if `rule.meta` property is empty.
-const emptyRuleMeta: RuleMeta = {
-  fixable: null,
-};
-
 /**
  * Load a plugin.
  *
@@ -120,27 +115,22 @@ async function loadPluginImpl(path: string): Promise<PluginDetails> {
     const ruleName = ruleNames[i],
       rule = rules[ruleName];
 
-    // Validate `rule.meta` and convert to object with standardized shape
-    // (all properties defined with default values if not supplied)
+    // Validate `rule.meta` and convert to vars with standardized shape
+    let isFixable = false;
     let ruleMeta = rule.meta;
-    if (ruleMeta == null) {
-      ruleMeta = emptyRuleMeta;
-    } else {
+    if (ruleMeta != null) {
       if (typeof ruleMeta !== 'object') throw new TypeError('Invalid `meta`');
 
-      let { fixable } = ruleMeta;
-      if (fixable === void 0) {
-        fixable = null;
-      } else if (fixable !== null && fixable !== 'code' && fixable !== 'whitespace') {
-        throw new TypeError('Invalid `meta.fixable`');
+      const { fixable } = ruleMeta;
+      if (fixable != null) {
+        if (fixable !== 'code' && fixable !== 'whitespace') throw new TypeError('Invalid `meta.fixable`');
+        isFixable = true;
       }
-
-      ruleMeta = { fixable };
     }
 
     // Create `Context` object for rule. This will be re-used for every file.
     // It's updated with file-specific data before linting each file with `setupContextForFile`.
-    const context = new Context(`${pluginName}/${ruleName}`, ruleMeta);
+    const context = new Context(`${pluginName}/${ruleName}`, isFixable);
 
     let ruleAndContext;
     if ('createOnce' in rule) {