fix(linter/plugins): reset visitor compilation state if error during compilation

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

@@ -274,6 +274,13 @@ export function resetFile() {
  * in the correct initial state for linting the next file.
  */
 export function resetStateAfterError() {
+  // In case error occurred during visitor compilation, clear internal state of visitor compilation,
+  // so no leftovers bleed into next file.
+  // We could have a separate function to reset state which could be simpler and faster, but `resetStateAfterError`
+  // should never be called - only happens when rules return an invalid visitor or malfunction.
+  // So better to use the existing function, rather than bloat the package with more code which should never run.
+  finalizeCompiledVisitor();
+
   diagnostics.length = 0;
   ancestors.length = 0;
   resetFile();

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

@@ -0,0 +1,7 @@
+{
+  "jsPlugins": ["./plugin.ts"],
+  "categories": { "correctness": "off" },
+  "rules": {
+    "error-plugin/error": "error"
+  }
+}

apps/oxlint/test/fixtures/lint_invalid_visitor/files/1.js

@@ -0,0 +1 @@
+let x;

apps/oxlint/test/fixtures/lint_invalid_visitor/files/2.js

@@ -0,0 +1 @@
+let y;

apps/oxlint/test/fixtures/lint_invalid_visitor/options.json

@@ -0,0 +1,3 @@
+{
+  "singleThread": true
+}

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

@@ -0,0 +1,22 @@
+# Exit code
+1
+
+# stdout
+```
+  x Error running JS plugin.
+  | File path: <fixture>/files/1.js
+  | TypeError: 'Program' property of visitor object is not a function
+
+  x error-plugin(error): Identifier in 2nd file: y
+   ,-[files/2.js:1:5]
+ 1 | let y;
+   :     ^
+   `----
+
+Found 0 warnings and 2 errors.
+Finished in Xms on 2 files with 1 rules using X threads.
+```
+
+# stderr
+```
+```

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

@@ -0,0 +1,64 @@
+import assert from "node:assert";
+
+import type { Plugin, Rule } from "#oxlint/plugins";
+
+// Aim of this test is:
+//
+// 1. Check that errors thrown during visitor compilation are handled correctly and shown to user as diagnostics.
+// 2. Check that global state is reset after an error during visiting a file, so it's in correct initial state
+//    when Oxlint starts linting the next file.
+//
+// The 2nd is tricky to test because usually the order Oxlint lints files in is non-deterministic.
+// To make this test deterministic, we run it with `oxlint --threads 1`
+// (`options.json` file for this fixture contains `"singleThread": true`).
+// This guarantees that `1.js` is linted before `2.js`.
+//
+// This rule throws an error during visitor compilation when linting 1st file. If global state is not reset properly
+// before linting 2nd file, `Identifier` visitor for 1st file will not be cleaned up and will fire on 2nd file.
+
+let fileIndex = 0;
+
+const rule: Rule = {
+  create(context) {
+    const isFirstFileLinted = fileIndex === 0;
+    fileIndex++;
+
+    // Check the order files get linted in is what we expect
+    const isFirstFile = context.filename.endsWith("1.js");
+    assert(isFirstFile === isFirstFileLinted);
+
+    if (isFirstFile) {
+      return {
+        Identifier(node) {
+          context.report({
+            message: `Identifier in 1st file: ${node.name}`,
+            node,
+          });
+        },
+
+        // Illegal value, causes error during visitor compilation
+        Program: 123 as any,
+      };
+    }
+
+    return {
+      Identifier(node) {
+        context.report({
+          message: `Identifier in 2nd file: ${node.name}`,
+          node,
+        });
+      },
+    };
+  },
+};
+
+const plugin: Plugin = {
+  meta: {
+    name: "error-plugin",
+  },
+  rules: {
+    error: rule,
+  },
+};
+
+export default plugin;