Prefer using exclusively Corepack when possible

.yarn/versions/2847fa24.yml

@@ -0,0 +1,23 @@
+releases:
+  "@yarnpkg/cli": major
+  "@yarnpkg/plugin-essentials": major
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/core"
+  - "@yarnpkg/doctor"

packages/acceptance-tests/pkg-tests-core/sources/utils/tests.ts

@@ -27,7 +27,7 @@ interface RunDriverOptions extends Record<string, any> {
   cwd?: PortablePath;
   projectFolder?: PortablePath;
   registryUrl: string;
-  env?: Record<string, string>;
+  env?: Record<string, string | undefined>;
 }
 
 export type PackageRunDriver = (

packages/acceptance-tests/pkg-tests-specs/sources/commands/set/version.test.ts

@@ -0,0 +1,130 @@
+import {xfs, ppath, PortablePath, Filename} from '@yarnpkg/fslib';
+
+const yarnrcRegexp = /^yarnPath:/;
+
+describe(`Commands`, () => {
+  describe(`set version`, () => {
+    test(
+      `it shouldn't set yarnPath if corepack is enabled and the version is semver`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: `/path/to/corepack`},
+      }, async ({path, run, source}) => {
+        await run(`set`, `version`, `3.0.0`);
+        await check(path, {corepackVersion: `3.0.0`, usePath: false});
+      }),
+    );
+
+    test(
+      `it should set yarnPath if corepack is disabled, even when the version is semver`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: undefined},
+      }, async ({path, run, source}) => {
+        await run(`set`, `version`, `3.0.0`);
+        await check(path, {corepackVersion: `3.0.0`, usePath: true});
+      }),
+    );
+
+    test(
+      `it should always set yarnPath if one already exists`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: `/path/to/corepack`},
+      }, async ({path, run, source}) => {
+        // To force yarnPath to be set; followed by a sanity check
+        await run(`set`, `version`, `3.0.0`, {env: {COREPACK_ROOT: undefined}});
+        await check(path, {corepackVersion: `3.0.0`, usePath: true});
+
+        await run(`set`, `version`, `3.0.0`);
+        await check(path, {corepackVersion: `3.0.0`, usePath: true});
+      }),
+    );
+
+    test(
+      `it should always set yarnPath if --yarn-path is set`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: `/path/to/corepack`},
+      }, async ({path, run, source}) => {
+        await run(`set`, `version`, `3.0.0`, `--yarn-path`);
+        await check(path, {corepackVersion: `3.0.0`, usePath: true});
+      }),
+    );
+
+    test(
+      `it should never set yarnPath if --no-yarn-path is set`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: undefined},
+      }, async ({path, run, source}) => {
+        await run(`set`, `version`, `3.0.0`, `--no-yarn-path`);
+        await check(path, {corepackVersion: `3.0.0`, usePath: false});
+      }),
+    );
+
+    test(
+      `it should prevent using --no-yarn-path with arbitrary files`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: undefined},
+      }, async ({path, run, source}) => {
+        const yarnIndirection = ppath.join(path, `custom-yarn.cjs` as Filename);
+        await xfs.writeFilePromise(yarnIndirection, ``);
+
+        await expect(run(`set`, `version`, yarnIndirection, `--no-yarn-path`)).rejects.toThrow();
+      }),
+    );
+
+    test(
+      `it should set yarnPath if the version is an arbitrary file`,
+      makeTemporaryEnv({}, {
+        env: {COREPACK_ROOT: undefined},
+      }, async ({path, run, source}) => {
+        const yarnIndirection = ppath.join(path, `custom-yarn.cjs` as Filename);
+        await xfs.writeFilePromise(yarnIndirection, ``);
+
+        await run(`set`, `version`, yarnIndirection);
+        await check(path, {corepackVersion: /[0-9]+\./, usePath: true});
+      }),
+    );
+  });
+});
+
+async function check(path: PortablePath, checks: {corepackVersion: string | RegExp, usePath: boolean}) {
+  const releasesPath = ppath.join(path, `.yarn/releases` as PortablePath);
+  const yarnrcPath = ppath.join(path, Filename.rc);
+  const manifestPath = ppath.join(path, Filename.manifest);
+
+  let releases: Array<string> | null;
+  try {
+    releases = await xfs.readdirPromise(releasesPath);
+  } catch (err) {
+    if (err.code === `ENOENT`) {
+      releases = null;
+    } else {
+      throw err;
+    }
+  }
+
+  let yarnrcFile;
+  try {
+    yarnrcFile = await xfs.readFilePromise(yarnrcPath, `utf8`);
+  } catch (err) {
+    if (err.code === `ENOENT`) {
+      yarnrcFile = ``;
+    } else {
+      throw err;
+    }
+  }
+
+  if (checks.usePath)
+    expect(releases).toHaveLength(1);
+  else
+    expect(releases).toEqual(null);
+
+  if (checks.usePath)
+    expect(yarnrcFile).toMatch(yarnrcRegexp);
+  else
+    expect(yarnrcFile).not.toMatch(yarnrcRegexp);
+
+  await expect(xfs.readJsonPromise(manifestPath)).resolves.toMatchObject({
+    packageManager: checks.corepackVersion instanceof RegExp
+      ? expect.stringMatching(`yarn@${checks.corepackVersion.source}`)
+      : `yarn@${checks.corepackVersion}`,
+  });
+}