fix(mapper): recognize aliased Express routers

CHANGELOG.md

@@ -10,6 +10,7 @@
 - Added `clawpatch review --export-tribunal-ledger` to emit review findings as JSONL for downstream ledger ingestion, thanks @dpdanpittman.
 - Added `clawpatch review --prompt-file` to append extra reviewer guidance from a file or stdin, thanks @dpdanpittman.
 - Added deterministic Express, Fastify, and Hono route mapping for Node projects, thanks @rohitjavvadi.
+- Fixed Express route mapping to recognize aliased Router factories from imports, CommonJS destructuring, and direct assignments, thanks @rohitjavvadi.
 - Added conservative Django `urls.py` route mapping for `path`, `re_path`, and legacy `url` declarations, thanks @rohitjavvadi.
 - Fixed provider commands with relative `--root` paths by canonicalizing explicit roots before invoking Codex or other providers.
 - Added first-pass Elixir Mix/Phoenix mapping for project metadata, contexts, Phoenix web slices, runtime config, Ecto migrations, project scripts, ExUnit tests, and Mix validation defaults, thanks @tears-mysthrala.

src/mapper.test.ts

@@ -1754,10 +1754,12 @@ describe("mapFeatures", () => {
       root,
       "src/server.ts",
       [
-        "import express, { Router } from 'express';",
+        "// route imports",
+        "import express, { Router, Router as ExpressRouter } from 'express';",
         "",
         "const app = express();",
         "const router = Router();",
+        "const aliasRouter = ExpressRouter();",
         "const typedRouter: Router = Router();",
         "const projectRouter = Router({ mergeParams: true });",
         "let hitCount = 0;",
@@ -1769,6 +1771,7 @@ describe("mapFeatures", () => {
         "app.get('/dynamic/' + version, dynamicRoute);",
         "app.all('/proxy', proxy);",
         "router.post('/admin/jobs', createJob);",
+        "aliasRouter.get('/aliased-router', listAliasedRouter);",
         "router.post<{ Body: CreateJob }>('/typed-jobs', createTypedJob);",
         "typedRouter.patch('/typed/:id', updateTyped);",
         "router.route('/users').get(listUsers).delete(deleteUsers);",
@@ -1787,6 +1790,7 @@ describe("mapFeatures", () => {
         "function dynamicRoute() {}",
         "function proxy() {}",
         "function createJob() {}",
+        "function listAliasedRouter() {}",
         "function createTypedJob() {}",
         "function updateTyped() {}",
         "function listUsers() {}",
@@ -1830,6 +1834,46 @@ describe("mapFeatures", () => {
         "",
       ].join("\n"),
     );
+    await writeFixture(
+      root,
+      "src/cjs-router.cjs",
+      [
+        "const { Router: CjsRouter, json: JsonFactory } = require('express');",
+        "",
+        "const cjsRouter = CjsRouter();",
+        "cjsRouter.get('/cjs-aliased-router', listCjsAliasedRouter);",
+        "const jsonFactory = JsonFactory();",
+        "jsonFactory.get('/cjs-not-router', ignored);",
+        "function listCjsAliasedRouter() {}",
+        "function ignored() {}",
+        "",
+      ].join("\n"),
+    );
+    await writeFixture(
+      root,
+      "src/router-assignment.ts",
+      [
+        "import express from 'express';",
+        "",
+        "const AssignedRouter = express.Router;",
+        "const TypedAssignedRouter: typeof express.Router = express.Router;",
+        "const RequiredRouter = require('express').Router;",
+        "const NotRouter = express.json;",
+        "const assignedRouter = AssignedRouter();",
+        "const typedAssignedRouter = TypedAssignedRouter();",
+        "const requiredRouter = RequiredRouter();",
+        "const notRouter = NotRouter();",
+        "assignedRouter.get('/assigned-router', listAssignedRouter);",
+        "typedAssignedRouter.get('/typed-assigned-router', listTypedAssignedRouter);",
+        "requiredRouter.get('/required-router', listRequiredRouter);",
+        "notRouter.get('/assigned-not-router', ignored);",
+        "function listAssignedRouter() {}",
+        "function listTypedAssignedRouter() {}",
+        "function listRequiredRouter() {}",
+        "function ignored() {}",
+        "",
+      ].join("\n"),
+    );
     await writeFixture(
       root,
       "src/hono.ts",
@@ -1866,12 +1910,21 @@ describe("mapFeatures", () => {
       "src/custom-router.ts",
       [
         "// import { Router } from 'express';",
-        "import { type Router } from 'express';",
+        "import { Router as CustomRouter } from './custom-router-factory';",
+        "import express from 'express';",
+        "import { type Router, type Router as ExpressRouter } from 'express';",
         "",
         "declare function Router(): { get(path: string, handler: unknown): void };",
+        "declare function ExpressRouter(): { get(path: string, handler: unknown): void };",
         "",
+        "const app = express();",
+        "const customRouter = CustomRouter();",
         "const router = Router();",
+        "const aliasRouter = ExpressRouter();",
+        "app.get('/custom-file-real', handler);",
+        "customRouter.get('/custom-import-router', handler);",
         "router.get('/custom-router', handler);",
+        "aliasRouter.get('/custom-alias-router', handler);",
         "function handler() {}",
         "",
       ].join("\n"),
@@ -1910,13 +1963,19 @@ describe("mapFeatures", () => {
         "Express route GET /anonymous",
         "Express route ALL /proxy",
         "Express route POST /admin/jobs",
+        "Express route GET /aliased-router",
+        "Express route GET /cjs-aliased-router",
+        "Express route GET /assigned-router",
+        "Express route GET /typed-assigned-router",
+        "Express route GET /required-router",
         "Express route POST /typed-jobs",
         "Express route PATCH /typed/:id",
         "Express route GET /users",
         "Express route DELETE /users",
         "Express route GET /reports",
         "Express route GET /projects/:projectId/items",
         "Express route GET /after-jsx-close",
+        "Express route GET /custom-file-real",
         "Fastify route GET /status",
         "Fastify route GET /typed-users/:id",
         "Fastify route GET /route-status",
@@ -1931,7 +1990,11 @@ describe("mapFeatures", () => {
     expect(titles).not.toContain("Express route GET /regex-health");
     expect(titles).not.toContain("Express route GET /arrow-regex");
     expect(titles).not.toContain("Express route GET /returned-regex");
+    expect(titles).not.toContain("Express route GET /custom-import-router");
     expect(titles).not.toContain("Express route GET /custom-router");
+    expect(titles).not.toContain("Express route GET /custom-alias-router");
+    expect(titles).not.toContain("Express route GET /cjs-not-router");
+    expect(titles).not.toContain("Express route GET /assigned-not-router");
     expect(titles).not.toContain("Express route GET /dynamic/");
     expect(titles).not.toContain("Fastify route GET /dynamic/");
     expect(titles).not.toContain("Fastify route GET /concat-");

src/mappers/node-routes.ts

@@ -302,8 +302,13 @@ function routeTargetNames(source: string, framework: ServerFramework): Set<strin
         "gu",
       ),
     ];
-    if (hasExpressRouterBinding(source)) {
-      patterns.push(new RegExp(`${declarationPrefix}Router${genericArguments}\\s*\\(`, "gu"));
+    for (const factoryName of expressRouterFactoryNames(source)) {
+      patterns.push(
+        new RegExp(
+          `${declarationPrefix}${escapeRegExp(factoryName)}${genericArguments}\\s*\\(`,
+          "gu",
+        ),
+      );
     }
     return declaredTargetNames(source, patterns);
   }
@@ -320,53 +325,89 @@ function routeTargetNames(source: string, framework: ServerFramework): Set<strin
   ]);
 }
 
-function hasExpressRouterBinding(source: string): boolean {
-  return (
-    hasExpressRouterImportBinding(source) ||
-    codePatternMatches(
-      source,
-      /\b(?:const|let|var)\s*\{\s*[^}]*\bRouter\b[^}]*\}\s*=\s*require\s*\(\s*["']express["']\s*\)/gu,
-    ) ||
-    codePatternMatches(
-      source,
-      /\b(?:const|let|var)\s+Router\s*=\s*(?:express\s*\.\s*Router|require\s*\(\s*["']express["']\s*\)\s*\.\s*Router)\b/gu,
-    )
-  );
+function expressRouterFactoryNames(source: string): Set<string> {
+  return new Set([
+    ...expressRouterImportBindingNames(source),
+    ...expressRouterRequireBindingNames(source),
+    ...expressRouterAssignmentNames(source),
+  ]);
 }
 
-function hasExpressRouterImportBinding(source: string): boolean {
-  const pattern = /\bimport\s+(?!type\b)([\s\S]{0,400}?)\bfrom\s*["']express["']/gu;
+function expressRouterImportBindingNames(source: string): Set<string> {
+  const names = new Set<string>();
+  const pattern =
+    /(?:^|[;\n])\s*import\s+(?!type\b)((?:(?!\n\s*import\b)[\s\S]){0,400}?)\bfrom\s*["']express["']/gu;
   pattern.lastIndex = 0;
   for (const match of source.matchAll(pattern)) {
-    if (isInsideCommentOrString(source, match.index ?? 0)) {
+    const importIndex = source.indexOf("import", match.index ?? 0);
+    if (importIndex < 0 || isInsideCommentOrString(source, importIndex)) {
       continue;
     }
-    if (importClauseHasBareValueRouter(match[1] ?? "")) {
-      return true;
-    }
+    addExpressRouterImportNames(names, match[1] ?? "");
   }
-  return false;
+  return names;
 }
 
-function importClauseHasBareValueRouter(clause: string): boolean {
+function addExpressRouterImportNames(names: Set<string>, clause: string): void {
   const named = /\{([^}]*)\}/u.exec(clause)?.[1];
   if (named === undefined) {
-    return false;
+    return;
   }
-  return named.split(",").some((part) => {
+  for (const part of named.split(",")) {
     const binding = part.trim();
-    return !binding.startsWith("type ") && /^Router(?:\s+as\s+Router)?$/u.test(binding);
-  });
+    if (binding.startsWith("type ")) {
+      continue;
+    }
+    const match = /^Router(?:\s+as\s+([A-Za-z_$][A-Za-z0-9_$]*))?$/u.exec(binding);
+    if (match !== null) {
+      names.add(match[1] ?? "Router");
+    }
+  }
 }
 
-function codePatternMatches(source: string, pattern: RegExp): boolean {
+function expressRouterRequireBindingNames(source: string): Set<string> {
+  const names = new Set<string>();
+  const pattern =
+    /\b(?:const|let|var)\s*\{\s*([^}]*)\}\s*=\s*require\s*\(\s*["']express["']\s*\)/gu;
   pattern.lastIndex = 0;
   for (const match of source.matchAll(pattern)) {
-    if (!isInsideCommentOrString(source, match.index ?? 0)) {
-      return true;
+    if (isInsideCommentOrString(source, match.index ?? 0)) {
+      continue;
     }
+    addExpressRouterRequireNames(names, match[1] ?? "");
   }
-  return false;
+  return names;
+}
+
+function addExpressRouterRequireNames(names: Set<string>, clause: string): void {
+  for (const part of clause.split(",")) {
+    const binding = part.trim();
+    const match = /^Router(?:\s*:\s*([A-Za-z_$][A-Za-z0-9_$]*))?$/u.exec(binding);
+    if (match !== null) {
+      names.add(match[1] ?? "Router");
+    }
+  }
+}
+
+function expressRouterAssignmentNames(source: string): Set<string> {
+  const names = new Set<string>();
+  const pattern =
+    /\b(?:const|let|var)\s+([A-Za-z_$][A-Za-z0-9_$]*)(?:\s*:\s*[^=;]+)?\s*=\s*(?:express\s*\.\s*Router|require\s*\(\s*["']express["']\s*\)\s*\.\s*Router)\b/gu;
+  pattern.lastIndex = 0;
+  for (const match of source.matchAll(pattern)) {
+    if (isInsideCommentOrString(source, match.index ?? 0)) {
+      continue;
+    }
+    const name = match[1];
+    if (name !== undefined) {
+      names.add(name);
+    }
+  }
+  return names;
+}
+
+function escapeRegExp(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/gu, "\\$&");
 }
 
 function declaredTargetNames(source: string, patterns: RegExp[]): Set<string> {