Apply build labels to images with only a FROM tag.

Signed-off-by: David Calavera <david.calavera@gmail.com>

builder/dockerfile/builder.go

@@ -222,6 +222,17 @@ func (b *Builder) build(config *types.ImageBuildOptions, context builder.Context
 			}
 			return "", err
 		}
+
+		// Commit the layer when there are only one children in
+		// the dockerfile, this is only the `FROM` tag, and
+		// build labels. Otherwise, the new image won't be
+		// labeled properly.
+		// Commit here, so the ID of the final image is reported
+		// properly.
+		if len(b.dockerfile.Children) == 1 && len(b.options.Labels) > 0 {
+			b.commit("", b.runConfig.Cmd, "")
+		}
+
 		shortImgID = stringid.TruncateID(b.image)
 		fmt.Fprintf(b.Stdout, " ---> %s\n", shortImgID)
 		if b.options.Remove {

builder/dockerfile/internals.go

@@ -418,7 +418,20 @@ func (b *Builder) processImageFrom(img builder.Image) error {
 		b.image = img.ImageID()
 
 		if img.RunConfig() != nil {
-			b.runConfig = img.RunConfig()
+			imgConfig := *img.RunConfig()
+			// inherit runConfig labels from the current
+			// state if they've been set already.
+			// Ensures that images with only a FROM
+			// get the labels populated properly.
+			if b.runConfig.Labels != nil {
+				if imgConfig.Labels == nil {
+					imgConfig.Labels = make(map[string]string)
+				}
+				for k, v := range b.runConfig.Labels {
+					imgConfig.Labels[k] = v
+				}
+			}
+			b.runConfig = &imgConfig
 		}
 	}
 

integration-cli/docker_cli_build_test.go

@@ -6680,11 +6680,9 @@ func (s *DockerSuite) TestBuildLabel(c *check.C) {
 	_, err := buildImage(name, `
   FROM `+minimalBaseImage()+`
   LABEL default foo
-`, false, []string{"--label", testLabel}...)
+`, false, "--label", testLabel)
 
-	if err != nil {
-		c.Fatal("error building image with labels", err)
-	}
+	c.Assert(err, checker.IsNil)
 
 	res := inspectFieldJSON(c, name, "Config.Labels")
 
@@ -6699,6 +6697,28 @@ func (s *DockerSuite) TestBuildLabel(c *check.C) {
 	}
 }
 
+func (s *DockerSuite) TestBuildLabelOneNode(c *check.C) {
+	name := "testbuildlabel"
+
+	_, err := buildImage(name, "FROM busybox", false, "--label", "foo=bar")
+
+	c.Assert(err, checker.IsNil)
+
+	res, err := inspectImage(name, "json .Config.Labels")
+	c.Assert(err, checker.IsNil)
+	var labels map[string]string
+
+	if err := json.Unmarshal([]byte(res), &labels); err != nil {
+		c.Fatal(err)
+	}
+
+	v, ok := labels["foo"]
+	if !ok {
+		c.Fatal("label `foo` not found in image")
+	}
+	c.Assert(v, checker.Equals, "bar")
+}
+
 func (s *DockerSuite) TestBuildLabelCacheCommit(c *check.C) {
 	name := "testbuildlabelcachecommit"
 	testLabel := "foo"
@@ -6713,11 +6733,9 @@ func (s *DockerSuite) TestBuildLabelCacheCommit(c *check.C) {
 	_, err := buildImage(name, `
   FROM `+minimalBaseImage()+`
   LABEL default foo
-`, true, []string{"--label", testLabel}...)
+`, true, "--label", testLabel)
 
-	if err != nil {
-		c.Fatal("error building image with labels", err)
-	}
+	c.Assert(err, checker.IsNil)
 
 	res := inspectFieldJSON(c, name, "Config.Labels")
 

integration-cli/docker_utils.go

@@ -890,6 +890,21 @@ func inspectMountPointJSON(j, destination string) (types.MountPoint, error) {
 	return *m, nil
 }
 
+func inspectImage(name, filter string) (string, error) {
+	args := []string{"inspect", "--type", "image"}
+	if filter != "" {
+		format := fmt.Sprintf("{{%s}}", filter)
+		args = append(args, "-f", format)
+	}
+	args = append(args, name)
+	inspectCmd := exec.Command(dockerBinary, args...)
+	out, exitCode, err := runCommandWithOutput(inspectCmd)
+	if err != nil || exitCode != 0 {
+		return "", fmt.Errorf("failed to inspect %s: %s", name, out)
+	}
+	return strings.TrimSpace(out), nil
+}
+
 func getIDByName(name string) (string, error) {
 	return inspectFieldWithError(name, "Id")
 }