Fix: invalid linking in workspaces for unused packages (#4129)

**Summary**

Fixes #4106. When a local package is listed under `workspaces` but that specific version is never used by anything, `yarn` still tries to install its bin links because it is listed as a dependency of the virtual workspace aggregator (but never get installed). This patch makes sure we have a location inside `node_modules` when trying to create bin links. It also fixes where we don't pass the proper location for workspaces root which may result in unexpected behavior under certain circumstances.

**Test plan**

Added a new test case which fails on master and passes with the fix.

Manual:
```
git clone [email protected]:babel/babel.git
yarn
```

Fails before the patch with latest nightly and passes after the patch.

Author: BYK

__tests__/commands/install/workspaces-install.js

@@ -132,6 +132,16 @@ test.concurrent(
   },
 );
 
+test.concurrent('install should not link a workspace if the version is not compatible', (): Promise<void> => {
+  return runInstall({binLinks: true}, 'workspaces-install-link-invalid', async (config): Promise<void> => {
+    // node_modules/left-pad - from npm
+    const packageFile = await fs.readFile(path.join(config.cwd, 'node_modules', 'left-pad', 'package.json'));
+    const readme = await fs.readFile(path.join(config.cwd, 'node_modules', 'left-pad', 'README.md'));
+    expect(JSON.parse(packageFile).version).not.toBe('1.1.2');
+    expect(readme.split('\n')[0]).not.toEqual('WORKSPACES ROCK!');
+  });
+});
+
 test.concurrent('install should prioritize non workspace dependency at root over the workspace symlink', (): Promise<
   void,
 > => {

__tests__/fixtures/install/workspaces-install-link-invalid/.yarnrc

@@ -0,0 +1 @@
+workspaces-experimental true

__tests__/fixtures/install/workspaces-install-link-invalid/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "my-project",
+  "private": true,
+  "devDependencies": {
+    "left-pad": "0.0.9"
+  },
+  "workspaces": [
+    "packages/*"
+  ]
+}

__tests__/fixtures/install/workspaces-install-link-invalid/packages/left-pad/README.md

@@ -0,0 +1 @@
+WORKSPACES ROCK!

__tests__/fixtures/install/workspaces-install-link-invalid/packages/left-pad/bin.js

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+
+var leftPad = require('./');
+
+console.log(leftPad(...process.argv.slice(0, 2)));

__tests__/fixtures/install/workspaces-install-link-invalid/packages/left-pad/index.js

@@ -0,0 +1,37 @@
+'use strict';
+module.exports = leftPad;
+
+var cache = ['', ' ', '  ', '   ', '    ', '     ', '      ', '       ', '        ', '         '];
+
+function leftPad(str, len, ch) {
+  // convert `str` to `string`
+  str = str + '';
+  // `len` is the `pad`'s length now
+  len = len - str.length;
+  // doesn't need to pad
+  if (len <= 0) return str;
+  // `ch` defaults to `' '`
+  if (!ch && ch !== 0) ch = ' ';
+  // convert `ch` to `string`
+  ch = ch + '';
+  // cache common use cases
+  if (ch === ' ' && len < 10) return cache[len] + str;
+  // `pad` starts with an empty string
+  var pad = '';
+  // loop
+  while (true) {
+    // add `ch` to `pad` if `len` is odd
+    if (len & 1) pad += ch;
+    // devide `len` by 2, ditch the fraction
+    len >>= 1;
+    // "double" the `ch` so this operation count grows logarithmically on `len`
+    // each time `ch` is "doubled", the `len` would need to be "doubled" too
+    // similar to finding a value in binary search tree, hence O(log(n))
+    if (len) ch += ch;
+    else
+      // `len` is 0, exit the loop
+      break;
+  }
+  // pad `str`!
+  return pad + str;
+}

__tests__/fixtures/install/workspaces-install-link-invalid/packages/left-pad/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "left-pad",
+  "version": "1.1.2",
+  "description": "String left pad",
+  "main": "index.js",
+  "bin": "bin.js",
+  "scripts": {
+    "test": "node test",
+    "bench": "node perf/perf.js"
+  },
+  "keywords": [
+    "leftpad",
+    "left",
+    "pad",
+    "padding",
+    "string",
+    "repeat"
+  ],
+  "repository": {
+    "url": "[email protected]:stevemao/left-pad.git",
+    "type": "git"
+  },
+  "author": "azer",
+  "maintainers": [
+    {
+      "name": "Cameron Westland",
+      "email": "[email protected]"
+    }
+  ],
+  "license": "WTFPL"
+}

__tests__/fixtures/install/workspaces-install-link-invalid/packages/left-pad/test.js

@@ -0,0 +1,13 @@
+var leftPad = require('./');
+var test = require('tape');
+
+test('left pad', function(assert) {
+  assert.plan(7);
+  assert.strictEqual(leftPad('foo', 5), '  foo');
+  assert.strictEqual(leftPad('foobar', 6), 'foobar');
+  assert.strictEqual(leftPad(1, 2, 0), '01');
+  assert.strictEqual(leftPad(1, 2, '-'), '-1');
+  assert.strictEqual(leftPad('foo', 2, ' '), 'foo');
+  assert.strictEqual(leftPad('foo', -1, ' '), 'foo');
+  assert.strictEqual(leftPad('foo', 7, 1), '1111foo');
+});

__tests__/fixtures/install/workspaces-install-link/packages/left-pad/bin.js

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+
+var leftPad = require('./');
+
+console.log(leftPad(...process.argv.slice(0, 2)));

src/cli/commands/install.js

@@ -275,15 +275,16 @@ export class Install {
       pushDeps('optionalDependencies', projectManifestJson, {hint: 'optional', optional: true}, true);
 
       if (this.config.workspacesEnabled) {
-        const workspaces = await this.config.resolveWorkspaces(path.dirname(loc), projectManifestJson);
+        const workspacesRoot = path.dirname(loc);
+        const workspaces = await this.config.resolveWorkspaces(workspacesRoot, projectManifestJson);
         workspaceLayout = new WorkspaceLayout(workspaces, this.config);
         // add virtual manifest that depends on all workspaces, this way package hoisters and resolvers will work fine
         const virtualDependencyManifest: Manifest = {
           _uid: '',
           name: `workspace-aggregator-${uuid.v4()}`,
           version: '1.0.0',
           _registry: 'npm',
-          _loc: '.',
+          _loc: workspacesRoot,
           dependencies: {},
         };
         workspaceLayout.virtualManifestName = virtualDependencyManifest.name;
@@ -293,7 +294,7 @@ export class Install {
         }
         const virtualDep = {};
         virtualDep[virtualDependencyManifest.name] = virtualDependencyManifest.version;
-        workspaces[virtualDependencyManifest.name] = {loc: '', manifest: virtualDependencyManifest};
+        workspaces[virtualDependencyManifest.name] = {loc: workspacesRoot, manifest: virtualDependencyManifest};
 
         pushDeps('workspaces', {workspaces: virtualDep}, {hint: 'workspaces', optional: false}, true);
       }