fix(linter/plugins): do not call before hook if empty visitor

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

@@ -60,6 +60,9 @@ const registeredPluginPaths = new Set<string>();
 // Indexed by `ruleId`, which is passed to `lintFile`.
 export const registeredRules: RuleAndContext[] = [];
 
+// `before` hook which makes rule never run.
+const neverRunBeforeHook: BeforeHook = () => false;
+
 // Plugin details returned to Rust
 interface PluginDetails {
   // Plugin name
@@ -146,6 +149,19 @@ async function loadPluginImpl(path: string): Promise<PluginDetails> {
       beforeHook = conformHookFn(beforeHook, 'before');
       afterHook = conformHookFn(afterHook, 'after');
 
+      // If empty visitor, make this rule never run by substituting a `before` hook which always returns `false`.
+      // This means the original `before` hook won't run either.
+      //
+      // Reason for doing this is:
+      // In future, we may do a check on Rust side whether AST contains any nodes which rules act on,
+      // and if not, skip calling into JS entirely. In that case, the `before` hook won't get called.
+      // We can't emulate that behavior exactly, but we can at least emulate it in this simple case,
+      // and prevent users defining rules with *only* a `before` hook, which they expect to run on every file.
+      if (ObjectKeys(visitor).length === 0) {
+        beforeHook = neverRunBeforeHook;
+        afterHook = null;
+      }
+
       ruleAndContext = { rule, context, visitor, beforeHook, afterHook };
     } else {
       ruleAndContext = { rule, context, visitor: null, beforeHook: null, afterHook: null };

apps/oxlint/test/fixtures/createOnce/.oxlintrc.json

@@ -6,6 +6,7 @@
     "create-once-plugin/skip-run": "error",
     "create-once-plugin/before-only": "error",
     "create-once-plugin/after-only": "error",
+    "create-once-plugin/only-hooks": "error",
     "create-once-plugin/no-hooks": "error"
   }
 }

apps/oxlint/test/fixtures/createOnce/plugin.ts

@@ -117,6 +117,20 @@ const afterOnlyRule: Rule = {
   },
 };
 
+const hooksOnlyRule: Rule = {
+  createOnce(context) {
+    return {
+      // Neither hook should be called, because no AST node visitor functions
+      before() {
+        context.report({ message: 'before hook: should not be output', node: SPAN });
+      },
+      after() {
+        context.report({ message: 'after hook: should not be output', node: SPAN });
+      },
+    };
+  },
+};
+
 const noHooksRule: Rule = {
   createOnce(context) {
     return {
@@ -139,6 +153,7 @@ const plugin: Plugin = {
     'skip-run': skipRunRule,
     'before-only': beforeOnlyRule,
     'after-only': afterOnlyRule,
+    'only-hooks': hooksOnlyRule,
     'no-hooks': noHooksRule,
   },
 };

apps/oxlint/test/fixtures/custom_plugin_lint_after_hook_error/output.snap.md

@@ -6,7 +6,7 @@
   x Error running JS plugin.
   | File path: <root>/apps/oxlint/test/fixtures/custom_plugin_lint_after_hook_error/files/index.js
   | Error: Whoops!
-  |     at after (<root>/apps/oxlint/test/fixtures/custom_plugin_lint_after_hook_error/plugin.ts:12:19)
+  |     at after (<root>/apps/oxlint/test/fixtures/custom_plugin_lint_after_hook_error/plugin.ts:13:19)
 
 Found 0 warnings and 1 error.
 Finished in Xms on 1 file using X threads.

apps/oxlint/test/fixtures/custom_plugin_lint_after_hook_error/plugin.ts

@@ -8,6 +8,7 @@ const plugin: Plugin = {
     error: {
       createOnce(_context) {
         return {
+          Program(_program) {},
           after() {
             throw new Error('Whoops!');
           },

apps/oxlint/test/fixtures/custom_plugin_lint_before_hook_error/plugin.ts

@@ -11,6 +11,7 @@ const plugin: Plugin = {
           before() {
             throw new Error('Whoops!');
           },
+          Program(_program) {},
         };
       },
     },

apps/oxlint/test/fixtures/definePlugin/output.snap.md

@@ -48,20 +48,6 @@
    : ^
    `----
 
-  x define-plugin-plugin(create-once-hooks-only): before hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
-  x define-plugin-plugin(create-once-hooks-only): after hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
   x define-plugin-plugin(create): ident visit fn "a":
   | filename: files/1.js
    ,-[files/1.js:1:5]
@@ -186,20 +172,6 @@
    : ^
    `----
 
-  x define-plugin-plugin(create-once-hooks-only): before hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
-  x define-plugin-plugin(create-once-hooks-only): after hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
   x define-plugin-plugin(create): ident visit fn "c":
   | filename: files/2.js
    ,-[files/2.js:1:5]
@@ -286,7 +258,7 @@
    :        ^
    `----
 
-Found 0 warnings and 39 errors.
+Found 0 warnings and 35 errors.
 Finished in Xms on 2 files using X threads.
 ```
 

apps/oxlint/test/fixtures/definePlugin/plugin.ts

@@ -187,6 +187,7 @@ const createOnceAfterOnlyRule: Rule = {
 const createOnceHooksOnlyRule: Rule = {
   createOnce(context) {
     return {
+      // Neither hook should be called, because no AST node visitor functions
       before() {
         context.report({
           message: 'before hook:\n' +

apps/oxlint/test/fixtures/definePlugin_and_defineRule/output.snap.md

@@ -48,20 +48,6 @@
    : ^
    `----
 
-  x define-plugin-and-rule-plugin(create-once-hooks-only): before hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
-  x define-plugin-and-rule-plugin(create-once-hooks-only): after hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
   x define-plugin-and-rule-plugin(create): ident visit fn "a":
   | filename: files/1.js
    ,-[files/1.js:1:5]
@@ -186,20 +172,6 @@
    : ^
    `----
 
-  x define-plugin-and-rule-plugin(create-once-hooks-only): before hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
-  x define-plugin-and-rule-plugin(create-once-hooks-only): after hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
   x define-plugin-and-rule-plugin(create): ident visit fn "c":
   | filename: files/2.js
    ,-[files/2.js:1:5]
@@ -286,7 +258,7 @@
    :        ^
    `----
 
-Found 0 warnings and 39 errors.
+Found 0 warnings and 35 errors.
 Finished in Xms on 2 files using X threads.
 ```
 

apps/oxlint/test/fixtures/definePlugin_and_defineRule/plugin.ts

@@ -186,6 +186,7 @@ const createOnceAfterOnlyRule = defineRule({
 const createOnceHooksOnlyRule = defineRule({
   createOnce(context) {
     return {
+      // Neither hook should be called, because no AST node visitor functions
       before() {
         context.report({
           message: 'before hook:\n' +

apps/oxlint/test/fixtures/defineRule/output.snap.md

@@ -48,20 +48,6 @@
    : ^
    `----
 
-  x define-rule-plugin(create-once-hooks-only): before hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
-  x define-rule-plugin(create-once-hooks-only): after hook:
-  | filename: files/1.js
-   ,-[files/1.js:1:1]
- 1 | let a, b;
-   : ^
-   `----
-
   x define-rule-plugin(create): ident visit fn "a":
   | filename: files/1.js
    ,-[files/1.js:1:5]
@@ -186,20 +172,6 @@
    : ^
    `----
 
-  x define-rule-plugin(create-once-hooks-only): before hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
-  x define-rule-plugin(create-once-hooks-only): after hook:
-  | filename: files/2.js
-   ,-[files/2.js:1:1]
- 1 | let c, d;
-   : ^
-   `----
-
   x define-rule-plugin(create): ident visit fn "c":
   | filename: files/2.js
    ,-[files/2.js:1:5]
@@ -286,7 +258,7 @@
    :        ^
    `----
 
-Found 0 warnings and 39 errors.
+Found 0 warnings and 35 errors.
 Finished in Xms on 2 files using X threads.
 ```
 

apps/oxlint/test/fixtures/defineRule/plugin.ts

@@ -186,6 +186,7 @@ const createOnceAfterOnlyRule = defineRule({
 const createOnceHooksOnlyRule = defineRule({
   createOnce(context) {
     return {
+      // Neither hook should be called, because no AST node visitor functions
       before() {
         context.report({
           message: 'before hook:\n' +

apps/oxlint/test/fixtures/sourceCode_late_access_after_only/plugin.ts

@@ -16,6 +16,7 @@ const SPAN: Node = {
 const createOnceRule: Rule = {
   createOnce(context) {
     return {
+      Program(_program) {},
       after() {
         context.report({
           message: 'after:\n' +