Updates 'set version' to shell out to Yarn 2 when requested

src/cli/commands/policies.js

@@ -2,10 +2,19 @@
 
 import type {Reporter} from '../../reporters/index.js';
 import type Config from '../../config.js';
+import {version} from '../../util/yarn-version.js';
+import * as child from '../../util/child.js';
 import buildSubCommands from './_build-sub-commands.js';
 import {getRcConfigForFolder} from '../../rc.js';
 import * as fs from '../../util/fs.js';
 import {stringify} from '../../lockfile';
+import {satisfiesWithPrereleases} from '../../util/semver.js';
+import {NODE_BIN_PATH} from '../../constants';
+
+const V2_NAMES = ['stable', 'berry', 'stable', 'canary', 'v2', '2'];
+
+const isLocalFile = (version: string) => version.match(/^\.{0,2}[\\/]/) || path.isAbsolute(version);
+const isV2Version = (version: string) => satisfiesWithPrereleases(version, '>=2.0.0');
 
 const chalk = require('chalk');
 const invariant = require('invariant');
@@ -49,6 +58,7 @@ async function fetchReleases(
 ): Promise<Array<Release>> {
   const token = process.env.GITHUB_TOKEN;
   const tokenUrlParameter = token ? `?access_token=${token}` : '';
+
   const request: Array<Release> = await config.requestManager.request({
     url: `https://api.github.com/repos/yarnpkg/yarn/releases${tokenUrlParameter}`,
     json: true,
@@ -98,32 +108,103 @@ export function hasWrapper(flags: Object, args: Array<string>): boolean {
 
 const {run, setFlags, examples} = buildSubCommands('policies', {
   async setVersion(config: Config, reporter: Reporter, flags: Object, args: Array<string>): Promise<void> {
-    let range = args[0] || 'latest';
-    let allowRc = flags.rc;
+    const initialRange = args[0] || 'latest';
+    let range = initialRange;
 
-    reporter.log(`Resolving ${chalk.yellow(range)} to a url...`);
+    let allowRc = flags.rc;
 
     if (range === 'rc') {
-      range = 'latest';
+      reporter.log(
+        `${chalk.yellow(
+          `Warning:`,
+        )} Your current Yarn binary is currently Yarn ${version}; to avoid potential breaking changes, 'set version rc' won't receive upgrades past the 1.22.x branch.\n         To upgrade to the latest versions, run ${chalk.cyan(
+          `yarn set version`,
+        )} ${chalk.yellow.underline(`canary`)} instead. Sorry for the inconvenience.\n`,
+      );
+
+      range = '*';
       allowRc = true;
     }
 
     if (range === 'latest') {
+      reporter.log(
+        `${chalk.yellow(
+          `Warning:`,
+        )} Your current Yarn binary is currently Yarn ${version}; to avoid potential breaking changes, 'set version latest' won't receive upgrades past the 1.22.x branch.\n         To upgrade to the latest versions, run ${chalk.cyan(
+          `yarn set version`,
+        )} ${chalk.yellow.underline(`stable`)} instead. Sorry for the inconvenience.\n`,
+      );
+
+      range = '*';
+    }
+
+    if (range === 'classic') {
       range = '*';
     }
 
     let bundleUrl;
     let bundleVersion;
-    let isV2 = false;
+    const isV2 = false;
 
     if (range === 'nightly' || range === 'nightlies') {
+      reporter.log(
+        `${chalk.yellow(
+          `Warning:`,
+        )} Nightlies only exist for Yarn 1.x; starting from 2.x onwards, you should use 'canary' instead`,
+      );
+
       bundleUrl = 'https://nightly.yarnpkg.com/latest.js';
       bundleVersion = 'nightly';
-    } else if (range === 'berry' || range === 'v2' || range === '2') {
-      bundleUrl = 'https://github.com/yarnpkg/berry/raw/master/packages/berry-cli/bin/berry.js';
-      bundleVersion = 'berry';
-      isV2 = true;
+    } else if (V2_NAMES.includes(range) || isLocalFile(range) || isV2Version(range)) {
+      const normalizedRange = range === `canary` ? `canary` : `stable`;
+
+      if (process.env.COREPACK_ROOT) {
+        await child.spawn(
+          NODE_BIN_PATH,
+          [
+            path.join(process.env.COREPACK_ROOT, 'dist/corepack.js'),
+            `yarn@${normalizedRange}`,
+            `set`,
+            `version`,
+            normalizedRange,
+          ],
+          {
+            stdio: 'inherit',
+            cwd: config.cwd,
+          },
+        );
+
+        return;
+      } else {
+        const bundle = await fetchBundle(
+          config,
+          'https://github.com/yarnpkg/berry/raw/master/packages/yarnpkg-cli/bin/yarn.js',
+        );
+
+        const yarnPath = path.resolve(config.lockfileFolder, `.yarn/releases/yarn-stable-temp.cjs`);
+        await fs.mkdirp(path.dirname(yarnPath));
+        await fs.writeFile(yarnPath, bundle);
+        await fs.chmod(yarnPath, 0o755);
+
+        try {
+          await child.spawn(NODE_BIN_PATH, [yarnPath, 'set', 'version', range], {
+            stdio: 'inherit',
+            cwd: config.lockfileFolder,
+            env: {
+              ...process.env,
+              YARN_IGNORE_PATH: `1`,
+            },
+          });
+        } catch (err) {
+          // eslint-disable-next-line no-process-exit
+          process.exit(1);
+        }
+
+        return;
+      }
     } else {
+      reporter.log(`Resolving ${chalk.yellow(initialRange)} to a url...`);
+
       let releases = [];
 
       try {