Improve command failure reporting

* Remove `#silence_build` method from `#exec.`
* Tell the user what happened when a command fails.
* Print both the command and error message for easier debugging.
* Capture both STDOUT and STDERR in #exec.

Commands may output important debugging information via either channel.
Use `Open3.capture2e` instead of `Kernel.system`. It appears to be
impossible to capture both `STDERR` and `STDOUT` simultaneously with the
latter.

CHANGELOG.md

@@ -1,10 +1,12 @@
 master
 ------
 
+* Improve command failure reporting. [#324]
 * Use latest EmberCLI-generated asset files. [#316]
 * Delete previous build output on application boot instead of on process exit.
   [#308]
 
+[#324]: https://github.com/thoughtbot/ember-cli-rails/pull/324
 [#316]: https://github.com/thoughtbot/ember-cli-rails/pull/316
 [#308]: https://github.com/thoughtbot/ember-cli-rails/pull/308
 

lib/ember_cli/runner.rb

@@ -0,0 +1,30 @@
+require "open3"
+
+module EmberCli
+  class Runner
+    def initialize(env: {}, out:, err:, options: {})
+      @env = env
+      @out = out
+      @err = err
+      @options = options
+    end
+
+    def run!(command)
+      output, status = Open3.capture2e(@env, command, @options)
+
+      @out.write(output)
+
+      unless status.success?
+        @err.write <<-MSG.strip_heredoc
+          ERROR: Failed command: `#{command}`
+          OUTPUT:
+            #{output}
+        MSG
+
+        exit 1
+      end
+
+      true
+    end
+  end
+end

lib/ember_cli/shell.rb

@@ -1,4 +1,5 @@
 require "ember_cli/command"
+require "ember_cli/runner"
 
 module EmberCli
   class Shell
@@ -13,7 +14,7 @@ def initialize(paths:, env: {}, options: {})
     end
 
     def compile
-      silence_build { exec ember.build }
+      exec ember.build
     end
 
     def build_and_watch
@@ -50,18 +51,17 @@ def test
     attr_reader :ember, :env, :options, :paths
 
     def spawn(command)
-      Kernel.spawn(env, command, process_options) || exit(1)
+      Kernel.spawn(env, command, chdir: paths.root.to_s, out: paths.log.to_s) ||
+        exit(1)
     end
 
     def exec(command)
-      Kernel.system(env, command, process_options) || exit(1)
-    end
-
-    def process_options
-      {
-        chdir: paths.root.to_s,
-        out: paths.log.to_s,
-      }
+      Runner.new(
+        options: { chdir: paths.root.to_s },
+        out: paths.log,
+        err: $stderr,
+        env: env,
+      ).run!(command)
     end
 
     def running?
@@ -77,13 +77,5 @@ def lock_buildfile
     def detach
       Process.detach pid
     end
-
-    def silence_build(&block)
-      if ENV.fetch("EMBER_CLI_RAILS_VERBOSE") { EmberCli.env.production? }
-        yield
-      else
-        silence_stream(STDOUT, &block)
-      end
-    end
   end
 end

spec/lib/ember_cli/runner_spec.rb

@@ -0,0 +1,34 @@
+require "ember_cli/runner"
+
+describe EmberCli::Runner do
+  describe "#run!" do
+    context "when the command fails" do
+      it "writes STDERR and STDOUT to `err`" do
+        out = StringIO.new
+        err = StringIO.new
+        runner = EmberCli::Runner.new(err: err, out: out)
+
+        expect { runner.run!("echo 'out'; echo 'err' > /dev/stderr; exit 1") }.
+          to raise_error(SystemExit)
+
+        [err, out].each(&:rewind)
+
+        expect(err.read).to match(/out\nerr/)
+        expect(out.read).to eq("out\nerr\n")
+      end
+    end
+
+    it "executes the command" do
+      out = StringIO.new
+      err = StringIO.new
+      runner = EmberCli::Runner.new(err: err, out: out)
+
+      runner.run!("echo 'out'")
+
+      [err, out].each(&:rewind)
+
+      expect(err.read).to be_empty
+      expect(out.read).to eq("out\n")
+    end
+  end
+end