From e4b0124887c2e1b854be9b3f22ee856c61d70d21 Mon Sep 17 00:00:00 2001
From: Timothee Guerin <tiguerin@microsoft.com>
Date: Fri, 11 Oct 2024 12:08:10 -0700
Subject: [PATCH] Fix resolve self priority (#4704)

---
 ...esolve-self-priority-2024-9-11-11-38-15.md |  7 +++++
 .gitignore                                    |  2 ++
 .../src/module-resolver/module-resolver.ts    | 31 +++++++++----------
 .../module-resolver/module-resolver.test.ts   | 27 ++++++++++++++++
 4 files changed, 50 insertions(+), 17 deletions(-)
 create mode 100644 .chronus/changes/fix-resolve-self-priority-2024-9-11-11-38-15.md

diff --git a/.chronus/changes/fix-resolve-self-priority-2024-9-11-11-38-15.md b/.chronus/changes/fix-resolve-self-priority-2024-9-11-11-38-15.md
new file mode 100644
index 0000000000..ff20886b42
--- /dev/null
+++ b/.chronus/changes/fix-resolve-self-priority-2024-9-11-11-38-15.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix order of resolution from node_modules and parent package
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index b9058dd743..6f59196ba6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -198,6 +198,8 @@ developer/
 
 *.vsix
 *.zip
+vite.config.ts.timestamp-*
+
 
 # Api extractor
 packages/*/etc/
diff --git a/packages/compiler/src/module-resolver/module-resolver.ts b/packages/compiler/src/module-resolver/module-resolver.ts
index 6b2b353150..e7fcbdfa68 100644
--- a/packages/compiler/src/module-resolver/module-resolver.ts
+++ b/packages/compiler/src/module-resolver/module-resolver.ts
@@ -6,7 +6,7 @@ import {
   InvalidPackageTargetError,
   NoMatchingConditionsError,
 } from "./esm/utils.js";
-import { parseNodeModuleSpecifier } from "./utils.js";
+import { NodeModuleSpecifier, parseNodeModuleSpecifier } from "./utils.js";
 
 // Resolve algorithm of node https://nodejs.org/api/modules.html#modules_all_together
 
@@ -126,10 +126,6 @@ export async function resolveModule(
     }
   }
 
-  // Try to resolve package itself.
-  const self = await resolveSelf(specifier, absoluteStart);
-  if (self) return self;
-
   // Try to resolve as a node_module package.
   const module = await resolveAsNodeModule(specifier, absoluteStart);
   if (module) return module;
@@ -154,19 +150,18 @@ export async function resolveModule(
   }
 
   /**
-   * Equivalent implementation to node LOAD_PACKAGE_SELF
-   * Resolve if the import is importing the current package.
+   * Try to import a package with that name in the current directory.
    */
-  async function resolveSelf(name: string, baseDir: string): Promise<ResolvedModule | undefined> {
-    for (const dir of listDirHierarchy(baseDir)) {
-      const pkgFile = resolvePath(dir, "package.json");
-      if (!(await isFile(host, pkgFile))) continue;
-      const pkg = await readPackage(host, pkgFile);
-      // 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;
+  async function resolveSelf(
+    { packageName, subPath }: NodeModuleSpecifier,
+    dir: string,
+  ): Promise<ResolvedModule | undefined> {
+    const pkgFile = resolvePath(dir, "package.json");
+    if (!(await isFile(host, pkgFile))) return undefined;
+    const pkg = await readPackage(host, pkgFile);
+    // 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 !== packageName) return undefined;
+    return loadPackage(dir, pkg, subPath);
   }
 
   /**
@@ -182,6 +177,8 @@ export async function resolveModule(
     const dirs = listDirHierarchy(baseDir);
 
     for (const dir of dirs) {
+      const self = await resolveSelf(module, dir);
+      if (self) return self;
       const n = await loadPackageAtPath(
         joinPaths(dir, "node_modules", module.packageName),
         module.subPath,
diff --git a/packages/compiler/test/module-resolver/module-resolver.test.ts b/packages/compiler/test/module-resolver/module-resolver.test.ts
index 76af657dbf..372b532f6f 100644
--- a/packages/compiler/test/module-resolver/module-resolver.test.ts
+++ b/packages/compiler/test/module-resolver/module-resolver.test.ts
@@ -399,4 +399,31 @@ describe("resolve self", () => {
       mainFile: "/ws/proj/entry.js",
     });
   });
+
+  it("prioritize local node_modules over self from multiple parent up", async () => {
+    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": "",
+      // @scope/proj installed locally
+      "/ws/proj/node_modules/test-lib/node_modules/@scope/proj/package.json": JSON.stringify({
+        name: "@scope/proj",
+        main: "entry.js",
+      }),
+      "/ws/proj/node_modules/test-lib/node_modules/@scope/proj/entry.js": "",
+    });
+
+    const resolved = await resolveModule(host, "@scope/proj", {
+      baseDir: "/ws/proj/node_modules/test-lib/nested",
+    });
+    const path = "/ws/proj/node_modules/test-lib/node_modules/@scope/proj";
+    expect(resolved).toMatchObject({
+      type: "module",
+      path,
+      mainFile: `${path}/entry.js`,
+    });
+  });
 });