Fix: Resolving self module keeps looking up (#4697)

.chronus/changes/fix-resolve-self-recursive-2024-9-11-9-8-33.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix module resolution when resolving self from within another package

packages/compiler/src/module-resolver/module-resolver.ts

@@ -162,11 +162,9 @@ export async function resolveModule(
       const pkgFile = resolvePath(dir, "package.json");
       if (!(await isFile(host, pkgFile))) continue;
       const pkg = await readPackage(host, pkgFile);
-      if (pkg.name === name) {
-        return loadPackage(dir, pkg);
-      } else {
-        return undefined;
-      }
+      // Node Spec says that you shouldn't lookup past the first package.json. However we used to support that so keeping this.
+      if (pkg.name !== name) continue;
+      return loadPackage(dir, pkg);
     }
     return undefined;
   }

packages/compiler/test/module-resolver/module-resolver.test.ts

@@ -374,3 +374,29 @@ describe("packages", () => {
     });
   });
 });
+
+describe("resolve self", () => {
+  const { host } = mkFs({
+    "/ws/proj/package.json": JSON.stringify({ name: "@scope/proj", main: "entry.js" }),
+    "/ws/proj/entry.js": "",
+    "/ws/proj/nested/index.js": "",
+    "/ws/proj/node_modules/test-lib/package.json": JSON.stringify({ main: "entry.js" }),
+    "/ws/proj/node_modules/test-lib/entry.js": "",
+    "/ws/proj/node_modules/test-lib/nested/index.js": "",
+  });
+
+  it.each([
+    ["at the same level", "/ws/proj"],
+    ["nested", "/ws/proj/nested"],
+    ["lookup parent package.json", "/ws/proj/node_modules/test-lib/nested"],
+  ])("%s", async (_, baseDir) => {
+    const resolved = await resolveModule(host, "@scope/proj", {
+      baseDir,
+    });
+    expect(resolved).toMatchObject({
+      type: "module",
+      path: "/ws/proj",
+      mainFile: "/ws/proj/entry.js",
+    });
+  });
+});