install: keep the scope when a yarn.lock npm: alias points at a scoped package

src/install/yarn.rs

@@ -236,34 +236,19 @@ impl<'a> Entry<'a> {
         ParsedNpmAlias { version: b"*" }
     }
 
+    /// Registry tarball URLs look like `<registry>/<name>/-/<basename>-<version>.tgz`,
+    /// where `<name>` spans two path segments (`@scope/name`) for scoped packages.
     pub(crate) fn get_package_name_from_resolved_url(url: &[u8]) -> Option<&[u8]> {
-        if let Some(dash_idx) = strings::index_of(url, b"/-/") {
-            let mut slash_count: usize = 0;
-            let mut last_slash: usize = 0;
-            let mut second_last_slash: usize = 0;
-
-            let mut i = dash_idx;
-            while i > 0 {
-                if url[i - 1] == b'/' {
-                    slash_count += 1;
-                    if slash_count == 1 {
-                        last_slash = i - 1;
-                    } else if slash_count == 2 {
-                        second_last_slash = i - 1;
-                        break;
-                    }
-                }
-                i -= 1;
-            }
-
-            if last_slash < dash_idx && url[last_slash + 1] == b'@' {
-                return Some(&url[second_last_slash + 1..dash_idx]);
-            } else if last_slash < dash_idx {
-                return Some(&url[last_slash + 1..dash_idx]);
-            }
+        let path = &url[..strings::index_of(url, b"/-/")?];
+        let (prefix, name) = strings::rsplit_once_char(path, b'/')?;
+        if name.is_empty() {
+            return None;
         }
-
-        None
+        let scope_start = strings::last_index_of_char(prefix, b'/').map_or(0, |slash| slash + 1);
+        if prefix[scope_start..].starts_with(b"@") {
+            return Some(&path[scope_start..]);
+        }
+        Some(name)
     }
 }
 

test/cli/install/migration/yarn-lock-migration.test.ts

@@ -810,6 +810,99 @@ undici-types@~5.26.4:
     expect(bunLockContent).toContain('"my-lodash": ["lodash@4.17.21"');
   });
 
+  test("yarn.lock with npm aliases of a scoped package keep the scope", async () => {
+    const typesNode20Integrity =
+      "sha512-g557vgQjUUfN76MZAN/dt1z3dzcUsimuysco0KeluHgrPdJXkP/XdAURgyO2W9fZWHRtRBiVKzKn8vyOAwlG+w==";
+    const typesNode18Integrity = "sha512-" + Buffer.alloc(64, 1).toString("base64");
+    const needsNodeTypesIntegrity = "sha512-" + Buffer.alloc(64, 2).toString("base64");
+
+    await using tmpDir = tempDir("yarn-migration-scoped-aliases", {
+      "package.json": JSON.stringify(
+        {
+          name: "scoped-alias-test",
+          version: "1.0.0",
+          dependencies: {
+            "@aliased/node-types": "npm:@types/node@20.11.5",
+            "@types/node": "^18.0.0",
+            "my-node-types": "npm:@types/node@20.11.5",
+            "needs-node-types": "1.0.0",
+          },
+        },
+        null,
+        2,
+      ),
+      // yarn v1 lists every pattern that resolved to the same tarball on one key line,
+      // so the three aliases of @types/node@20.11.5 share a single entry.
+      "yarn.lock": `# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+"@aliased/node-types@npm:@types/node@20.11.5", "my-node-types@npm:@types/node@20.11.5", "types-alias@npm:@types/node@20.11.5":
+  version "20.11.5"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-20.11.5.tgz#be10c622ca7fcaa3cf226cf80166abc31389d86e"
+  integrity ${typesNode20Integrity}
+
+"@types/node@^18.0.0":
+  version "18.19.0"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-18.19.0.tgz#1111111111111111111111111111111111111111"
+  integrity ${typesNode18Integrity}
+
+needs-node-types@1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/needs-node-types/-/needs-node-types-1.0.0.tgz#2222222222222222222222222222222222222222"
+  integrity ${needsNodeTypesIntegrity}
+  dependencies:
+    types-alias "npm:@types/node@20.11.5"
+`,
+    });
+
+    // After migrating, bun fetches the manifest of every migrated package by the name it
+    // recorded, so the registry sees which package each alias was resolved to.
+    const requestedManifests = new Set<string>();
+    await using registry = Bun.serve({
+      port: 0,
+      fetch(req) {
+        requestedManifests.add(decodeURIComponent(new URL(req.url).pathname.slice(1)));
+        return new Response("not found", { status: 404 });
+      },
+    });
+
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), "pm", "migrate", "-f"],
+      cwd: tmpDir,
+      env: {
+        ...bunEnv,
+        BUN_CONFIG_REGISTRY: registry.url.href,
+        BUN_INSTALL_CACHE_DIR: join(tmpDir, ".bun-cache"),
+      },
+      stdout: "pipe",
+      stderr: "pipe",
+      stdin: "ignore",
+    });
+
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+    expect(stdout).toBe("");
+    expect(stderr).toContain("migrated lockfile from yarn.lock");
+    expect(exitCode).toBe(0);
+
+    const lock = Bun.JSONC.parse(await Bun.file(join(tmpDir, "bun.lock")).text()) as { packages: unknown };
+    expect(lock.packages).toStrictEqual({
+      "@aliased/node-types": ["@types/node@20.11.5", "", {}, typesNode20Integrity],
+      "@types/node": ["@types/node@18.19.0", "", {}, typesNode18Integrity],
+      "my-node-types": ["@types/node@20.11.5", "", {}, typesNode20Integrity],
+      "needs-node-types": [
+        "needs-node-types@1.0.0",
+        "",
+        { dependencies: { "types-alias": "npm:@types/node@20.11.5" } },
+        needsNodeTypesIntegrity,
+      ],
+      "types-alias": ["@types/node@20.11.5", "", {}, typesNode20Integrity],
+    });
+
+    expect([...requestedManifests].sort()).toStrictEqual(["@types/node", "needs-node-types"]);
+  });
+
   test("yarn.lock with resolutions", async () => {
     await using tmpDir = tempDir("yarn-migration-resolutions", {
       "package.json": JSON.stringify(