Implement package-json mixin.

lib/actions/package-json.js

@@ -0,0 +1,53 @@
+'use strict';
+
+/**
+ * @mixin
+ * @alias actions/packege-json
+ */
+module.exports = (cls) =>
+  class extends cls {
+    /**
+     * @private
+     * Resolve the dependencies to be added to the package.json.
+     *
+     * @param {Object|string|string[]} dependencies
+     * @return {Promise} a 'packageName: packageVersion' object
+     */
+    async _resolvePackageJsonDependencies(dependencies) {
+      if (typeof dependencies === 'string') {
+        dependencies = [dependencies];
+      } else if (typeof dependencies !== 'object') {
+        throw new TypeError(
+          'resolvePackageJsonDependencies requires an object'
+        );
+      } else if (!Array.isArray(dependencies)) {
+        return dependencies;
+      }
+
+      const entries = await Promise.all(
+        dependencies.map((dependency) => this.env.resolvePackage(dependency))
+      );
+      return Object.fromEntries(entries);
+    }
+
+    /**
+     * @private
+     * Add dependencies to be added to the package.json.
+     *
+     * @param {Object|string|string[]} dependencies
+     * @return {Promise} a 'packageName: packageVersion' object
+     */
+    async addDependencies(dependencies) {
+      dependencies = await this._resolvePackageJsonDependencies(dependencies);
+      this.packageJson.merge({dependencies});
+      return dependencies;
+    }
+
+    async addDevDependencies(devDependencies) {
+      devDependencies = await this._resolvePackageJsonDependencies(
+        devDependencies
+      );
+      this.packageJson.merge({devDependencies});
+      return devDependencies;
+    }
+  };

lib/index.js

@@ -20,6 +20,11 @@ const EMPTY = '@@_YEOMAN_EMPTY_MARKER_@@';
 const debug = createDebug('yeoman:generator');
 const ENV_VER_WITH_VER_API = '2.9.0';
 
+const mixins = [require('./actions/package-json')];
+
+// eslint-disable-next-line unicorn/no-reduce
+const Base = mixins.reduce((a, b) => b(a), EventEmitter);
+
 // Ensure a prototype method is a candidate run by default
 const methodIsValid = function (name) {
   return !['_', '#'].includes(name.charAt(0)) && name !== 'constructor';
@@ -82,7 +87,7 @@ const runGenerator = (generator) => {
  * @typedef {Function} WrappedMethod
  */
 
-class Generator extends EventEmitter {
+class Generator extends Base {
   // If for some reason environment adds more queues, we should use or own for stability.
   static get queues() {
     return [
@@ -965,6 +970,9 @@ class Generator extends EventEmitter {
     );
   }
 
+  /**
+   * Generator config Storage.
+   */
   get config() {
     if (!this._config) {
       this._config = this._getStorage();
@@ -973,6 +981,17 @@ class Generator extends EventEmitter {
     return this._config;
   }
 
+  /**
+   * Package.json Storage.
+   */
+  get packageJson() {
+    if (!this._packageJson) {
+      this._packageJson = this.createStorage('package.json');
+    }
+
+    return this._packageJson;
+  }
+
   /**
    * Ignore cancellable tasks.
    */
@@ -1228,6 +1247,8 @@ class Generator extends EventEmitter {
 
       // Reset the storage
       this._config = undefined;
+      // Reset packageJson
+      this._packageJson = undefined;
     }
 
     return this._destinationRoot || this.env.cwd;
@@ -1329,6 +1350,7 @@ class Generator extends EventEmitter {
 _.extend(Generator.prototype, require('./actions/help'));
 _.extend(Generator.prototype, require('./actions/spawn-command'));
 _.extend(Generator.prototype, require('./actions/fs'));
+_.extend(Generator.prototype, require('./actions/package-json'));
 Generator.prototype.user = require('./actions/user');
 
 module.exports = Generator;

test/package-json.js

@@ -0,0 +1,110 @@
+'use strict';
+const assert = require('assert');
+const os = require('os');
+const path = require('path');
+const makeDir = require('make-dir');
+const rimraf = require('rimraf');
+const Environment = require('yeoman-environment');
+
+const Base = require('..');
+
+const tmpdir = path.join(os.tmpdir(), 'yeoman-package-json');
+
+describe('Base#package-json', function () {
+  this.timeout(10000);
+  let generator;
+  let env;
+
+  beforeEach(function () {
+    this.prevCwd = process.cwd();
+    this.tmp = tmpdir;
+    makeDir.sync(path.join(tmpdir, 'subdir'));
+    process.chdir(tmpdir);
+
+    env = Environment.createEnv();
+    const Generator = class extends Base {};
+    Generator.prototype.exec = function () {};
+    generator = new Generator({
+      env
+    });
+  });
+
+  afterEach(function (done) {
+    process.chdir(this.prevCwd);
+    rimraf(tmpdir, done);
+  });
+
+  describe('_resolvePackageJsonDependencies()', () => {
+    it('should accept semver version', async () => {
+      assert.deepStrictEqual(
+        await generator._resolvePackageJsonDependencies('yeoman-generator@^2'),
+        {'yeoman-generator': '^2'}
+      );
+    });
+
+    it('should accept github repository', async () => {
+      assert.deepStrictEqual(
+        await generator._resolvePackageJsonDependencies(
+          'yeoman/generator#v4.13.0'
+        ),
+        {'yeoman-generator': 'github:yeoman/generator#v4.13.0'}
+      );
+    });
+
+    it('should accept github repository version', async () => {
+      assert.deepStrictEqual(
+        await generator._resolvePackageJsonDependencies(
+          'yeoman-generator@yeoman/generator#v4.13.0'
+        ),
+        {'yeoman-generator': 'github:yeoman/generator#v4.13.0'}
+      );
+    });
+
+    it('should accept object and return it', async () => {
+      const a = {};
+      assert.strictEqual(await generator._resolvePackageJsonDependencies(a), a);
+    });
+
+    it('should accept arrays', async () => {
+      assert.deepStrictEqual(
+        await generator._resolvePackageJsonDependencies([
+          'yeoman-generator@^2',
+          'yeoman-environment@^2'
+        ]),
+        {'yeoman-generator': '^2', 'yeoman-environment': '^2'}
+      );
+    });
+  });
+
+  describe('addDependencies()', () => {
+    it('should generate dependencies inside package.json', async () => {
+      await generator.addDependencies('yeoman-generator@^2');
+      assert.deepStrictEqual(generator.packageJson.getAll(), {
+        dependencies: {'yeoman-generator': '^2'}
+      });
+    });
+
+    it('should accept object and merge inside package.json', async () => {
+      await generator.addDependencies({'yeoman-generator': '^2'});
+      assert.deepStrictEqual(generator.packageJson.getAll(), {
+        dependencies: {'yeoman-generator': '^2'}
+      });
+    });
+  });
+
+  describe('addDependencies()', () => {
+    it('should generate dependencies inside package.json', async () => {
+      await generator.addDevDependencies('yeoman-generator@^2');
+      assert.deepStrictEqual(generator.packageJson.getAll(), {
+        devDependencies: {'yeoman-generator': '^2'}
+      });
+    });
+
+    it('should accept object and merge devDependencies inside package.json', async () => {
+      await generator.addDevDependencies({'yeoman-generator': '^2'});
+      assert.deepStrictEqual(generator.packageJson.getAll(), {
+        devDependencies: {'yeoman-generator': '^2'}
+      });
+    });
+  });
+});