fix: resolve jsconfig.json path aliases, not just tsconfig.json

tests/skill/understand/test_extract_import_map.test.mjs

@@ -528,6 +528,71 @@ describe('extract-import-map.mjs — TypeScript / JavaScript resolver', () => {
     expect(result.output.importMap['src/app.ts']).toContain('lib/thing.ts');
   });
 
+  // ── jsconfig.json path aliases ──────────────────────────────────────────
+  //
+  // `create-next-app` writes jsconfig.json (not tsconfig.json) when you
+  // decline TypeScript, carrying the identical `compilerOptions.paths`.
+  // Matching only the literal filename "tsconfig.json" meant every alias in a
+  // JS-only Next.js project resolved to nothing, so the graph lost all of its
+  // app→lib import edges.
+
+  it('resolves jsconfig.json paths aliases in a JS-only project', () => {
+    projectRoot = setupTree({
+      'jsconfig.json': JSON.stringify({
+        compilerOptions: {
+          baseUrl: '.',
+          paths: { '@/*': ['./*'] },
+        },
+      }),
+      'app/page.js': `import { x } from '@/lib/thing.js';\nconst _ = x;\n`,
+      'lib/thing.js': `export const x = 1;\n`,
+    });
+
+    const result = runScript(projectRoot, {
+      projectRoot,
+      files: [
+        { path: 'jsconfig.json', language: 'json', fileCategory: 'config' },
+        { path: 'app/page.js', language: 'javascript', fileCategory: 'code' },
+        { path: 'lib/thing.js', language: 'javascript', fileCategory: 'code' },
+      ],
+    });
+
+    expect(result.status).toBe(0);
+    expect(result.output.importMap['app/page.js']).toContain('lib/thing.js');
+  });
+
+  it('prefers tsconfig.json over jsconfig.json when a directory holds both', () => {
+    // A vestigial jsconfig alongside a real tsconfig must not win, whichever
+    // order the parallel reads happen to complete in. Only the tsconfig alias
+    // (@ts/*) resolves; the jsconfig-only alias (@js/*) does not.
+    projectRoot = setupTree({
+      'tsconfig.json': JSON.stringify({
+        compilerOptions: { paths: { '@ts/*': ['./lib/*'] } },
+      }),
+      'jsconfig.json': JSON.stringify({
+        compilerOptions: { paths: { '@js/*': ['./lib/*'] } },
+      }),
+      'src/app.ts': `import { x } from '@ts/thing';\nimport { y } from '@js/other';\nconst _ = x + y;\n`,
+      'lib/thing.ts': `export const x = 1;\n`,
+      'lib/other.ts': `export const y = 2;\n`,
+    });
+
+    const result = runScript(projectRoot, {
+      projectRoot,
+      files: [
+        { path: 'tsconfig.json', language: 'json', fileCategory: 'config' },
+        { path: 'jsconfig.json', language: 'json', fileCategory: 'config' },
+        { path: 'src/app.ts', language: 'typescript', fileCategory: 'code' },
+        { path: 'lib/thing.ts', language: 'typescript', fileCategory: 'code' },
+        { path: 'lib/other.ts', language: 'typescript', fileCategory: 'code' },
+      ],
+    });
+
+    expect(result.status).toBe(0);
+    expect(result.output.importMap['src/app.ts']).toContain('lib/thing.ts');
+    expect(result.output.importMap['src/app.ts']).not.toContain('lib/other.ts');
+  });
+
   // ── #294: NodeNext / ESM TypeScript `.js → .ts` rewrite ────────────────
   //
   // Under `moduleResolution: NodeNext`, TypeScript does NOT rewrite import

understand-anything-plugin/skills/understand/extract-import-map.mjs

@@ -316,6 +316,12 @@ function parseTsConfigText(raw) {
  * failure for a specific tsconfig, emits a Warning: pointing at the bad
  * file and skips it (the rest of the project keeps working).
  *
+ * `jsconfig.json` is read on equal footing: JavaScript-only projects
+ * (notably `create-next-app` without TypeScript) declare the very same
+ * `compilerOptions.paths` aliases there, and editors and bundlers honor it
+ * identically. When a directory holds both, tsconfig.json wins — a project
+ * carrying both is a TypeScript project whose jsconfig is vestigial.
+ *
  * Parse strategy (per-file, in parseTsConfigText):
  *   1. Try the comment-stripped text (handles JSONC-style tsconfigs).
  *   2. If that fails, retry the ORIGINAL raw text — recovers the case
@@ -332,18 +338,22 @@ async function loadTsConfigs(projectRoot, files) {
   for (const f of files) {
     const p = toPosix(f.path);
     const base = p.includes('/') ? p.slice(p.lastIndexOf('/') + 1) : p;
-    if (base !== 'tsconfig.json') continue;
+    if (base !== 'tsconfig.json' && base !== 'jsconfig.json') continue;
     const absPath = join(projectRoot, p);
     if (!existsSync(absPath)) continue;
     candidates.push({ key: p, absPath });
   }
   const reads = await readFilesParallel(candidates);
+  // Which basename supplied each directory's config, so a tsconfig.json can
+  // override a jsconfig.json regardless of the order the parallel reads land.
+  const wonBy = new Map();
   for (const { key: p, raw, err } of reads) {
+    const base = p.includes('/') ? p.slice(p.lastIndexOf('/') + 1) : p;
     if (err) {
       failures.push({ path: p, stage: 'resolver-config-read', message: err.message });
       // absPath isn't carried through the helper return shape; reconstruct it.
       warnings.push(
-        `Warning: extract-import-map: tsconfig.json at ${join(projectRoot, p)} failed ` +
+        `Warning: extract-import-map: ${base} at ${join(projectRoot, p)} failed ` +
         `to read (${err.message}) — path aliases from this config will ` +
         `not be applied — relative imports unaffected\n`,
       );
@@ -354,16 +364,19 @@ async function loadTsConfigs(projectRoot, files) {
       failures.push({
         path: p,
         stage: 'resolver-config-parse',
-        message: 'invalid tsconfig.json',
+        message: `invalid ${base}`,
       });
       warnings.push(
-        `Warning: extract-import-map: tsconfig.json at ${join(projectRoot, p)} failed ` +
+        `Warning: extract-import-map: ${base} at ${join(projectRoot, p)} failed ` +
         `to parse — path aliases from this config will not be applied ` +
         `— relative imports unaffected\n`,
       );
       continue;
     }
-    out.set(dirOf(p), parsed);
+    const dir = dirOf(p);
+    if (wonBy.get(dir) === 'tsconfig.json' && base !== 'tsconfig.json') continue;
+    out.set(dir, parsed);
+    wonBy.set(dir, base);
   }
   return { configs: out, warnings, failures };
 }