make env override env file, not the other way around

Author: aduh95

sources/specUtils.ts

@@ -156,7 +156,7 @@ export async function loadSpec(initialCwd: string): Promise<LoadSpecResult> {
     data: any;
     manifestPath: string;
     envFilePath?: string;
-    localEnv?: LocalEnvFile;
+    localEnv: LocalEnvFile;
   } | null = null;
 
   while (nextCwd !== currCwd && (!selection || !selection.data.packageManager)) {
@@ -184,15 +184,17 @@ export async function loadSpec(initialCwd: string): Promise<LoadSpecResult> {
     if (typeof data !== `object` || data === null)
       throw new UsageError(`Invalid package.json in ${path.relative(initialCwd, manifestPath)}`);
 
-    let localEnv: LocalEnvFile | undefined;
-    const envFilePath = path.join(currCwd, `.corepack.env`);
+    let localEnv: LocalEnvFile;
+    const envFilePath = path.resolve(currCwd, `./.corepack.env`);
     debugUtils.log(`Checking ${envFilePath}`);
     try {
-      localEnv = {...process.env, ...parseEnv(await fs.promises.readFile(envFilePath, `utf8`))};
+      localEnv = {...parseEnv(await fs.promises.readFile(envFilePath, `utf8`)), ...process.env};
+      debugUtils.log(`Successfully loaded env file found at ${envFilePath}`);
     } catch (err) {
       if ((err as NodeError)?.code !== `ENOENT`)
         throw err;
 
+      debugUtils.log(`No env file found at ${envFilePath}`);
       localEnv = process.env;
     }
 

tests/main.test.ts

@@ -294,6 +294,47 @@ it(`should use hash from "packageManager" even when "devEngines" defines a diffe
   });
 });
 
+it(`should use hash from env even when "devEngines" defines a different one`, async () => {
+  await xfs.mktempPromise(async cwd => {
+    await xfs.writeJsonPromise(ppath.join(cwd, `package.json` as PortablePath), {
+      devEngines: {
+        packageManager: {
+          name: `yarn`,
+          version: `3.0.0-rc.2+sha224.f83f6d1cbfac10ba6b516a62ccd2a72ccd857aa6c514d1cd7185ec60`,
+        },
+      },
+    });
+
+    process.env.COREPACK_DEV_ENGINES_YARN = `3.0.0-rc.2+sha224.deadbeef`;
+    await expect(runCli(cwd, [`yarn`, `--version`])).resolves.toMatchObject({
+      exitCode: 1,
+      stderr: /Mismatch hashes. Expected deadbeef, got f83f6d1cbfac10ba6b516a62ccd2a72ccd857aa6c514d1cd7185ec60/,
+      stdout: ``,
+    });
+  });
+});
+
+it(`should use hash from env even when ".corepack.env" defines a different one`, async () => {
+  await xfs.mktempPromise(async cwd => {
+    await xfs.writeJsonPromise(ppath.join(cwd, `package.json` as PortablePath), {
+      devEngines: {
+        packageManager: {
+          name: `yarn`,
+          version: `3.0.0-rc.2`,
+        },
+      },
+    });
+    await xfs.writeFilePromise(ppath.join(cwd, `.corepack.env` as PortablePath), `COREPACK_DEV_ENGINES_YARN=3.0.0-rc.2+sha1.bedabb1e\n`);
+
+    process.env.COREPACK_DEV_ENGINES_YARN = `3.0.0-rc.2+sha224.deadbeef`;
+    await expect(runCli(cwd, [`yarn`, `--version`])).resolves.toMatchObject({
+      exitCode: 1,
+      stderr: /Mismatch hashes. Expected bedabb1e, got 694bdad81703169e203febd57f9dc97d3be867bd/,
+      stdout: ``,
+    });
+  });
+});
+
 describe(`should accept range in devEngines only if a specific version is provided`, () => {
   it(`either in .corepack.env`, async() => {
     await xfs.mktempPromise(async cwd => {