Enhance rake ember:install to fully reinstall if necessary.

Closes [#394].

EmberCLI ships with [`ember-cli-dependency-checker`][addon], which
exposes the `ember version` command.

`ember version` is akin to `bundle check`.

This commit enhances the `ember:install` Rake task to cleanup frontend
 dependencies before installing if `ember version` returns a non-zero
exit status.

This (in conjunction with [`npm shrinkwrap`][shrinkwrap]) helps to
ensure that every machine has the same dependencies installed.

[#394]: #394
[addon]: https://github.com/quaertym/ember-cli-dependency-checker
[shrinkwrap]: https://github.com/quaertym/ember-cli-dependency-checker#deployment-with-shrinkwrap

CHANGELOG.md

@@ -1,9 +1,11 @@
 master
 ------
 
+* Enhance `rake ember:install` to fully reinstall if necessary. [#396]
 * `EmberCli::Deploy::File` serves assets with Rails' `static_cache_control`
   value. [#403]
 
+[#396]: https://github.com/thoughtbot/ember-cli-rails/pull/396
 [#403]: https://github.com/thoughtbot/ember-cli-rails/pull/403
 
 0.7.1

lib/ember_cli/path_set.rb

@@ -78,10 +78,18 @@ def bower
       end
     end
 
+    def bower_components
+      @bower_components ||= root.join("bower_components")
+    end
+
     def npm
       @npm ||= app_options.fetch(:npm_path) { which("npm") }
     end
 
+    def node_modules
+      @node_modules ||= root.join("node_modules")
+    end
+
     def tee
       @tee ||= app_options.fetch(:tee_path) { which("tee") }
     end

lib/ember_cli/runner.rb

@@ -9,19 +9,25 @@ def initialize(env: {}, out:, err:, options: {})
       @options = options
     end
 
-    def run!(command)
+    def run(command)
       output, status = Open3.capture2e(@env, command, @options)
 
       @out.write(output)
 
+      [output, status]
+    end
+
+    def run!(command)
+      output, status = run(command)
+
       unless status.success?
         @err.write <<-MSG.strip_heredoc
           ERROR: Failed command: `#{command}`
           OUTPUT:
             #{output}
         MSG
 
-        exit 1
+        exit status.exitstatus
       end
 
       true

lib/ember_cli/shell.rb

@@ -14,7 +14,7 @@ def initialize(paths:, env: {}, options: {})
     end
 
     def compile
-      exec ember.build
+      run! ember.build
     end
 
     def build_and_watch
@@ -34,22 +34,45 @@ def stop
 
     def install
       if paths.gemfile.exist?
-        exec "#{paths.bundler} install"
+        run! "#{paths.bundler} install"
       end
 
-      exec "#{paths.npm} prune && #{paths.npm} install"
-      exec "#{paths.bower} prune && #{paths.bower} install"
+      if invalid_ember_dependencies?
+        clean_ember_dependencies!
+      end
+
+      run! "#{paths.npm} prune && #{paths.npm} install"
+      run! "#{paths.bower} prune && #{paths.bower} install"
     end
 
     def test
-      exec ember.test
+      run! ember.test
     end
 
     private
 
     attr_accessor :pid
     attr_reader :ember, :env, :options, :paths
 
+    delegate :run, :run!, to: :runner
+
+    def invalid_ember_dependencies?
+      !run("#{paths.ember} version")
+    rescue DependencyError
+      false
+    end
+
+    def clean_ember_dependencies!
+      ember_dependency_directories.select(&:exist?).each(&:rmtree)
+    end
+
+    def ember_dependency_directories
+      [
+        paths.node_modules,
+        paths.bower_components,
+      ]
+    end
+
     def spawn(command)
       Kernel.spawn(
         env,
@@ -59,13 +82,13 @@ def spawn(command)
       ) || exit(1)
     end
 
-    def exec(command)
+    def runner
       Runner.new(
         options: { chdir: paths.root.to_s },
         out: paths.log,
         err: $stderr,
         env: env,
-      ).run!(command)
+      )
     end
 
     def running?

spec/lib/ember_cli/path_set_spec.rb

@@ -127,6 +127,17 @@
     end
   end
 
+  describe "#bower_components" do
+    it "is a child of #root" do
+      app = build_app(name: "foo")
+
+      path_set = build_path_set(app: app)
+
+      expect(path_set.bower_components).
+        to eq rails_root.join("foo", "bower_components")
+    end
+  end
+
   describe "#npm" do
     it "can be overridden" do
       app = build_app(options: { npm_path: "npm-path" })
@@ -145,6 +156,16 @@
     end
   end
 
+  describe "#node_modules" do
+    it "is a child of #root" do
+      app = build_app(name: "foo")
+
+      path_set = build_path_set(app: app)
+
+      expect(path_set.node_modules).to eq rails_root.join("foo", "node_modules")
+    end
+  end
+
   describe "#tee" do
     it "can be overridden" do
       app = build_app(options: { tee_path: "tee-path" })