Adds versioning to the cache path (#2768)

* Adds versioning to the cache path

* Adds a test to check that the cache path is correctly updated

* Renames "cacheFolder" into "versionedCacheFolder"

* Adds a test to check that the cache is correctly busted when bumping the cache version

* Fixes tests on Windows

* Changes variable names

__tests__/commands/install/integration.js

@@ -1,5 +1,8 @@
 /* @flow */
 
+import type Config from '../../../src/config';
+import PackageResolver from '../../../src/package-resolver.js';
+import {run as cache} from '../../../src/cli/commands/cache.js';
 import {run as check} from '../../../src/cli/commands/check.js';
 import * as constants from '../../../src/constants.js';
 import * as reporters from '../../../src/reporters/index.js';
@@ -11,15 +14,41 @@ import {promisify} from '../../../src/util/promise';
 
 jasmine.DEFAULT_TIMEOUT_INTERVAL = 150000;
 
-const request = require('request');
+let request = require('request');
 const assert = require('assert');
 const semver = require('semver');
 const fsNode = require('fs');
 const path = require('path');
+const stream = require('stream');
 const os = require('os');
 
+async function mockConstants(base: Config, mocks: Object, cb: (config: Config) => Promise<void>): Promise<void> {
+  // We cannot put this function inside _helpers, because we need to change the "request" variable
+  // after resetting the modules. Updating this variable is required because some tests check what
+  // happened during the Yarn execution, and they need to use the same instance of "request" than
+  // the Yarn environment.
+
+  const opts = {};
+
+  opts.binLinks = base.binLinks;
+  opts.cwd = base.cwd;
+  opts.globalFolder = base.globalFolder;
+  opts.linkFolder = base.linkFolder;
+  opts.production = base.production;
+  opts.cacheFolder = base._cacheRootFolder;
+
+  const automock = jest.genMockFromModule('../../../src/constants');
+  jest.setMock('../../../src/constants', Object.assign(automock, mocks));
+
+  jest.resetModules();
+  request = require('request');
+
+  jest.mock('../../../src/constants');
+  await cb(await require('../../../src/config.js').default.create(opts, base.reporter));
+  jest.unmock('../../../src/constants');
+}
+
 beforeEach(request.__resetAuthedRequests);
-// $FlowFixMe
 afterEach(request.__resetAuthedRequests);
 
 test.concurrent('properly find and save build artifacts', async () => {
@@ -37,6 +66,48 @@ test.concurrent('properly find and save build artifacts', async () => {
   });
 });
 
+test('changes the cache path when bumping the cache version', async () => {
+  await runInstall({}, 'install-github', async (config): Promise<void> => {
+    const inOut = new stream.PassThrough();
+    const reporter = new reporters.JSONReporter({stdout: inOut});
+
+    await cache(config, reporter, {}, ['dir']);
+    assert.ok(!!(JSON.parse(String(inOut.read())) : any).data.match(/[\\\/]v1[\\\/]?$/));
+
+    await mockConstants(config, {CACHE_VERSION: 42}, async (config): Promise<void> => {
+      await cache(config, reporter, {}, ['dir']);
+      assert.ok(!!(JSON.parse(String(inOut.read())) : any).data.match(/[\\\/]v42[\\\/]?$/));
+    });
+  });
+});
+
+test('changes the cache directory when bumping the cache version', async () => {
+  await runInstall({}, 'install-production', async (config, reporter): Promise<void> => {
+    const lockfile = await Lockfile.fromDirectory(config.cwd);
+
+    const resolver = new PackageResolver(config, lockfile);
+    await resolver.init([{pattern: 'is-array', registry: 'npm'}]);
+
+    const ref = resolver.getPackageReferences()[0];
+    const cachePath = config.generateHardModulePath(ref, true);
+
+    await fs.writeFile(path.join(cachePath, 'yarn.test'), 'YARN TEST');
+    await fs.unlink(path.join(config.cwd, 'node_modules'));
+
+    const firstReinstall = new Install({skipIntegrityCheck: true}, config, reporter, lockfile);
+    await firstReinstall.init();
+
+    assert.ok(await fs.exists(path.join(config.cwd, 'node_modules', 'is-array', 'yarn.test')));
+
+    await mockConstants(config, {CACHE_VERSION: 42}, async (config): Promise<void> => {
+      const secondReinstall = new Install({skipIntegrityCheck: true}, config, reporter, lockfile);
+      await secondReinstall.init();
+
+      assert.ok(!await fs.exists(path.join(config.cwd, 'node_modules', 'is-array', 'yarn.test')));
+    });
+  });
+});
+
 test.concurrent("removes extraneous files that aren't in module or artifacts", async () => {
   async function check(cwd: string): Promise<void> {
     // retains artifact

__tests__/package-resolver.js

@@ -30,18 +30,21 @@ function addTest(pattern, registry = 'npm', init: ?(cacheFolder: string) => Prom
     const reporter = new reporters.NoopReporter({});
 
     const loc = await makeTemp();
-    await fs.mkdirp(path.join(loc, 'node_modules'));
     const cacheFolder = path.join(loc, 'cache');
-    await fs.mkdirp(cacheFolder);
-    if (init) {
-      await init(cacheFolder);
-    }
 
     const config = await Config.create({
       cwd: loc,
       offline,
       cacheFolder,
     }, reporter);
+
+    await fs.mkdirp(path.join(loc, 'node_modules'));
+    await fs.mkdirp(config.cacheFolder);
+
+    if (init) {
+      await init(config.cacheFolder);
+    }
+
     const resolver = new PackageResolver(config, lockfile);
     await resolver.init([{pattern, registry}]);