Fix for issue yeoman/yo#518

lib/environment.js

@@ -9,6 +9,7 @@ const escapeStrRe = require('escape-string-regexp');
 const untildify = require('untildify');
 const memFs = require('mem-fs');
 const debug = require('debug')('yeoman:environment');
+const isScoped = require('is-scoped');
 const Store = require('./store');
 const resolver = require('./resolver');
 const TerminalAdapter = require('./adapter');
@@ -338,13 +339,21 @@ class Environment extends EventEmitter {
     const Generator = this.get(namespace);
 
     if (typeof Generator !== 'function') {
+      let generatorHint = '';
+      if (isScoped(namespace)) {
+        const splitName = namespace.split('/');
+        generatorHint = `${splitName[0]}/generator-${splitName[1]}`;
+      } else {
+        generatorHint = `generator-${namespace}`;
+      }
+
       return this.error(
         new Error(
           chalk.red('You don\'t seem to have a generator with the name “' + namespace + '” installed.') + '\n' +
           'But help is on the way:\n\n' +
           'You can see available generators via ' +
           chalk.yellow('npm search yeoman-generator') + ' or via ' + chalk.yellow('http://yeoman.io/generators/') + '. \n' +
-          'Install them with ' + chalk.yellow('npm install generator-' + namespace) + '.\n\n' +
+          'Install them with ' + chalk.yellow(`npm install ${generatorHint}`) + '.\n\n' +
           'To see all your installed generators run ' + chalk.yellow('yo') + ' without any arguments. ' +
           'Adding the ' + chalk.yellow('--help') + ' option will also show subgenerators. \n\n' +
           'If ' + chalk.yellow('yo') + ' cannot find the generator, run ' + chalk.yellow('yo doctor') + ' to troubleshoot your system.'

package.json

@@ -37,6 +37,7 @@
     "globby": "^6.1.0",
     "grouped-queue": "^0.3.0",
     "inquirer": "^3.0.1",
+    "is-scoped": "^1.0.0",
     "lodash": "^4.11.1",
     "log-symbols": "^1.0.1",
     "mem-fs": "^1.1.0",

test/environment.js

@@ -246,6 +246,13 @@ describe('Environment', () => {
     it('returns the generator', function () {
       assert.ok(this.env.run('stub:run') instanceof Generator);
     });
+
+    it('correctly append scope in generator hint', function () {
+      this.env.on('error', err => {
+        assert.ok(err.message.indexOf('@dummyscope/generator-package') >= 0);
+      });
+      this.env.run('@dummyscope/package');
+    });
   });
 
   describe('#registerModulePath()', () => {