command/build: build error machine-readable is targetted to the build

command/build/command.go

@@ -188,9 +188,17 @@ func (c Command) Run(env packer.Environment, args []string) int {
 
 	if len(errors) > 0 {
 		env.Ui().Machine("error-count", strconv.FormatInt(int64(len(errors)), 10))
+
 		env.Ui().Error("\n==> Some builds didn't complete successfully and had errors:")
 		for name, err := range errors {
-			env.Ui().Machine("error", name, err.Error())
+			// Create a UI for the machine readable stuff to be targetted
+			ui := &packer.TargettedUi{
+				Target: name,
+				Ui:     env.Ui(),
+			}
+
+			ui.Machine("error", err.Error())
+
 			env.Ui().Error(fmt.Sprintf("--> %s: %s", name, err))
 		}
 	}

website/source/docs/machine-readable/command-build.html.markdown

@@ -147,18 +147,15 @@ of `packer build`.
 		</p>
 	</dd>
 
-	<dt>error (2)</dt>
+	<dt>error (1)</dt>
 	<dd>
 		<p>
-		A build error that occurred.
+		A build error that occurred. The target of this output will be
+		the build that had the error.
 		</p>
 
 		<p>
-		<strong>Data 1: name</strong> - The name of the build that had an error.
+		<strong>Data 1: error</strong> - The error message as a string.
-		</p>
-
-		<p>
-		<strong>Data 2: error</strong> - The error message as a string.
 		</p>
 	</dd>
 </dl>