fix(extraction): index CommonJS export assignments as functions (#1675) (#1771)

`exports.getItems = async (req, res) => {…}` and `module.exports.x =
function () {…}` — the Express controller style — produced no symbol: the
arrow's parent is an assignment, not a declarator, so it stayed anonymous,
its calls attributed to the file, and `node`/`callers` answered "Symbol
not found" for a route-wired handler. Resolve the name from the export
property, mark it exported, in both the wasm walker and the kernel.

Co-authored-by: danusha2345 <ewidusoc498@gmail.com>
Co-authored-by: Colby McHenry <colbymchenry@users.noreply.github.com>

__tests__/commonjs-exports.test.ts

@@ -0,0 +1,71 @@
+/**
+ * CommonJS export assignments name the function they hold (#1675).
+ *
+ * `exports.getItems = async (req, res) => {…}` and `module.exports.x =
+ * function () {…}` are how Express controllers are commonly written. The
+ * arrow is anonymous only syntactically — the export property is the name
+ * every `router.get('/items', getItems)` resolves — so it gets the same
+ * treatment `const getItems = () => {}` already has: a function node, exported,
+ * with its calls attributed to it rather than to the file.
+ */
+import { describe, it, expect, beforeAll } from 'vitest';
+import { extractFromSource } from '../src/extraction';
+import { initGrammars, loadAllGrammars } from '../src/extraction/grammars';
+
+beforeAll(async () => {
+  await initGrammars();
+  await loadAllGrammars();
+});
+
+const refsFrom = (result: ReturnType<typeof extractFromSource>, id: string) =>
+  result.unresolvedReferences.filter((r) => r.fromNodeId === id).map((r) => r.referenceName);
+
+describe('CommonJS export assignments', () => {
+  it('indexes exports.X / module.exports.X functions as exported function nodes', () => {
+    const code = `
+const { findItems, removeItem } = require('./db');
+
+exports.getItems = async (req, res) => {
+  res.json(await findItems());
+};
+
+module.exports.deleteItem = function (req, res) {
+  removeItem(req.params.id);
+  res.end();
+};
+
+exports.plain = 42;
+module.exports = { legacy: 1 };
+`;
+    const result = extractFromSource('src/controller.js', code);
+    const fns = result.nodes.filter((n) => n.kind === 'function');
+    expect(fns.map((n) => n.name).sort()).toEqual(['deleteItem', 'getItems']);
+
+    const getItems = fns.find((n) => n.name === 'getItems')!;
+    const deleteItem = fns.find((n) => n.name === 'deleteItem')!;
+    expect(getItems.startLine).toBe(4);
+    expect(getItems.isExported).toBe(true);
+    expect(deleteItem.isExported).toBe(true);
+    expect(getItems.isAsync).toBe(true);
+
+    // The handlers' calls are their own, not the file's.
+    expect(refsFrom(result, getItems.id)).toContain('findItems');
+    expect(refsFrom(result, deleteItem.id)).toContain('removeItem');
+    const file = result.nodes.find((n) => n.kind === 'file')!;
+    expect(refsFrom(result, file.id)).not.toContain('findItems');
+    expect(refsFrom(result, file.id)).not.toContain('removeItem');
+
+    // A non-function export is not a function, and nothing is left anonymous.
+    expect(result.nodes.map((n) => n.name)).not.toContain('<anonymous>');
+  });
+
+  it('leaves other member assignments alone', () => {
+    const code = `
+const handlers = {};
+handlers.onSave = () => { persist(); };
+app.locals.format = function () { return 1; };
+`;
+    const result = extractFromSource('src/other.js', code);
+    expect(result.nodes.filter((n) => n.kind === 'function')).toEqual([]);
+  });
+});

__tests__/fixtures/kernel-parity/torture.js

@@ -74,6 +74,11 @@ export default {
   },
 };
 
+// --- CommonJS export assignments (#1675) -----------------------------------
+exports.getItems = async (req, res) => { res.json(await findItems()); };
+module.exports.deleteItem = function (req, res) { removeItem(req.params.id); res.end(); };
+exports.plain = 42;
+handlers.onSave = () => { persist(); };
 // --- call-expression receivers (#1683) ----------------------------------------
 function bucketChains(d, k, v) {
   d.setdefault(k, []).append(v);