feat(bin): Implement an optional parameter support to yarn bin (#5739)

* feat(bin): Implement an optional parameter support to `yarn bin`

This allows to get the path to a binary without making assumptions regarding the layout of the
`node_modules` folder.

BREAKING CHANGE: n/a

n/a

* Adds `yarn bin` tests

* Update en.js

* Update bin.js

* Update bin.js

* Fixes the tests

__tests__/commands/bin.js

@@ -0,0 +1,26 @@
+/* @flow */
+
+import {run as buildRun, runInstall} from './_helpers.js';
+import {BufferReporter} from '../../src/reporters/index.js';
+import {run} from '../../src/cli/commands/bin.js';
+
+const path = require('path');
+
+const fixturesLoc = path.join(__dirname, '..', 'fixtures', 'bin');
+const runBin = buildRun.bind(null, BufferReporter, fixturesLoc, (args, flags, config, reporter): Promise<void> => {
+  return run(config, reporter, flags, args);
+});
+
+test('running bin without arguments should return the folder where the binaries are stored', (): Promise<void> => {
+  return runBin([], {}, '../install/install-production-bin', (config, reporter): ?Promise<void> => {
+    expect(reporter.getBufferText()).toMatch(/[\\\/]node_modules[\\\/]\.bin[\\\/]?$/);
+  });
+});
+
+test('running bin with a binary name as the argument should return its full path', (): Promise<void> => {
+  return runInstall({binLinks: true}, 'install-production-bin', async (config): ?Promise<void> => {
+    const reporter = new BufferReporter();
+    await run(config, reporter, {}, ['rimraf']);
+    expect(reporter.getBufferText()).toMatch(/[\\\/]node_modules[\\\/]\.bin[\\\/]rimraf$/);
+  });
+});

src/cli/commands/bin.js

@@ -4,6 +4,7 @@ import type {Reporter} from '../../reporters/index.js';
 import type Config from '../../config.js';
 import RegistryYarn from '../../resolvers/registries/yarn-resolver.js';
 
+const fs = require('fs');
 const path = require('path');
 
 export function hasWrapper(commander: Object): boolean {
@@ -16,6 +17,16 @@ export function setFlags(commander: Object) {
 
 export function run(config: Config, reporter: Reporter, flags: Object, args: Array<string>): Promise<void> {
   const binFolder = path.join(config.cwd, config.registries[RegistryYarn.registry].folder, '.bin');
-  reporter.log(binFolder, {force: true});
+  if (args.length === 0) {
+    reporter.log(binFolder, {force: true});
+  } else {
+    const binName = args[0];
+    const finalPath = path.normalize(`${binFolder}/${binName}`);
+    if (fs.existsSync(finalPath)) {
+      reporter.log(finalPath, {force: true});
+    } else {
+      reporter.error(reporter.lang('packageBinaryNotFound', binName));
+    }
+  }
   return Promise.resolve();
 }

src/reporters/lang/en.js

@@ -356,6 +356,7 @@ const messages = {
   packageInstalledWithBinaries: 'Installed $0 with binaries:',
   packageHasBinaries: '$0 has binaries:',
   packageHasNoBinaries: '$0 has no binaries',
+  packageBinaryNotFound: "Couldn't find a binary named $0",
 
   couldBeDeduped: '$0 could be deduped from $1 to $2',
   lockfileNotContainPattern: 'Lockfile does not contain pattern: $0',