@@ -68,7 +68,7 @@ func env(b *Builder, args []string, attributes map[string]bool, original string)

 		// value ==> args[j+1]

 		if len(args[j]) == 0 {

-			return fmt.Errorf("ENV names can not be blank")

+			return errBlankCommandNames("ENV")

 		}

 		newVar := args[j] + "=" + args[j+1] + ""

@@ -136,7 +136,7 @@ func label(b *Builder, args []string, attributes map[string]bool, original strin

 		// value ==> args[j+1]

 		if len(args[j]) == 0 {

-			return fmt.Errorf("LABEL names can not be blank")

+			return errBlankCommandNames("LABEL")

 		}

 		newVar := args[j] + "=" + args[j+1] + ""

@@ -455,7 +455,7 @@ func parseOptInterval(f *Flag) (time.Duration, error) {

 //

 func healthcheck(b *Builder, args []string, attributes map[string]bool, original string) error {

 	if len(args) == 0 {

-		return fmt.Errorf("HEALTHCHECK requires an argument")

+		return errAtLeastOneArgument("HEALTHCHECK")

 	}

 	typ := strings.ToUpper(args[0])

 	args = args[1:]

@@ -529,11 +529,7 @@ func healthcheck(b *Builder, args []string, attributes map[string]bool, original

 		b.runConfig.Healthcheck = &healthcheck

 	}

-	if err := b.commit("", b.runConfig.Cmd, fmt.Sprintf("HEALTHCHECK %q", b.runConfig.Healthcheck)); err != nil {

-		return err

-	}

-

-	return nil

+	return b.commit("", b.runConfig.Cmd, fmt.Sprintf("HEALTHCHECK %q", b.runConfig.Healthcheck))

 }

 // ENTRYPOINT /usr/sbin/nginx

@@ -654,7 +650,7 @@ func volume(b *Builder, args []string, attributes map[string]bool, original stri

 	for _, v := range args {

 		v = strings.TrimSpace(v)

 		if v == "" {

-			return fmt.Errorf("Volume specified can not be an empty string")

+			return fmt.Errorf("VOLUME specified can not be an empty string")

 		}

 		b.runConfig.Volumes[v] = struct{}{}

 	}

@@ -669,7 +665,7 @@ func volume(b *Builder, args []string, attributes map[string]bool, original stri

 // Set the signal that will be used to kill the container.

 func stopSignal(b *Builder, args []string, attributes map[string]bool, original string) error {

 	if len(args) != 1 {

-		return fmt.Errorf("STOPSIGNAL requires exactly one argument")

+		return errExactlyOneArgument("STOPSIGNAL")

 	}

 	sig := args[0]

@@ -689,7 +685,7 @@ func stopSignal(b *Builder, args []string, attributes map[string]bool, original

 // Dockerfile author may optionally set a default value of this variable.

 func arg(b *Builder, args []string, attributes map[string]bool, original string) error {

 	if len(args) != 1 {

-		return fmt.Errorf("ARG requires exactly one argument definition")

+		return errExactlyOneArgument("ARG")

 	}

 	var (

@@ -707,7 +703,7 @@ func arg(b *Builder, args []string, attributes map[string]bool, original string)

 	if strings.Contains(arg, "=") {

 		parts := strings.SplitN(arg, "=", 2)

 		if len(parts[0]) == 0 {

-			return fmt.Errorf("ARG names can not be blank")

+			return errBlankCommandNames("ARG")

 		}

 		name = parts[0]

@@ -764,6 +760,10 @@ func errAtLeastTwoArguments(command string) error {

 	return fmt.Errorf("%s requires at least two arguments", command)

 }

+func errBlankCommandNames(command string) error {

+	return fmt.Errorf("%s names can not be blank", command)

+}

+

 func errTooManyArguments(command string) error {

 	return fmt.Errorf("Bad input to %s, too many arguments", command)

 }

@@ -22,7 +22,8 @@ func TestCommandsExactlyOneArgument(t *testing.T) {

 		{"MAINTAINER", func(args []string) error { return maintainer(nil, args, nil, "") }},

 		{"FROM", func(args []string) error { return from(nil, args, nil, "") }},

 		{"WORKDIR", func(args []string) error { return workdir(nil, args, nil, "") }},

-		{"USER", func(args []string) error { return user(nil, args, nil, "") }}}

+		{"USER", func(args []string) error { return user(nil, args, nil, "") }},

+		{"STOPSIGNAL", func(args []string) error { return stopSignal(nil, args, nil, "") }}}

 	for _, command := range commands {

 		err := command.function([]string{})

@@ -31,9 +32,9 @@ func TestCommandsExactlyOneArgument(t *testing.T) {

 			t.Fatalf("Error should be present for %s command", command.name)

 		}

-		expectedError := fmt.Sprintf("%s requires exactly one argument", command.name)

+		expectedError := errExactlyOneArgument(command.name)

-		if err.Error() != expectedError {

+		if err.Error() != expectedError.Error() {

 			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)

 		}

 	}

@@ -44,6 +45,7 @@ func TestCommandsAtLeastOneArgument(t *testing.T) {

 		{"ENV", func(args []string) error { return env(nil, args, nil, "") }},

 		{"LABEL", func(args []string) error { return label(nil, args, nil, "") }},

 		{"ONBUILD", func(args []string) error { return onbuild(nil, args, nil, "") }},

+		{"HEALTHCHECK", func(args []string) error { return healthcheck(nil, args, nil, "") }},

 		{"EXPOSE", func(args []string) error { return expose(nil, args, nil, "") }},

 		{"VOLUME", func(args []string) error { return volume(nil, args, nil, "") }}}

@@ -54,9 +56,9 @@ func TestCommandsAtLeastOneArgument(t *testing.T) {

 			t.Fatalf("Error should be present for %s command", command.name)

 		}

-		expectedError := fmt.Sprintf("%s requires at least one argument", command.name)

+		expectedError := errAtLeastOneArgument(command.name)

-		if err.Error() != expectedError {

+		if err.Error() != expectedError.Error() {

 			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)

 		}

 	}

@@ -74,9 +76,9 @@ func TestCommandsAtLeastTwoArguments(t *testing.T) {

 			t.Fatalf("Error should be present for %s command", command.name)

 		}

-		expectedError := fmt.Sprintf("%s requires at least two arguments", command.name)

+		expectedError := errAtLeastTwoArguments(command.name)

-		if err.Error() != expectedError {

+		if err.Error() != expectedError.Error() {

 			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)

 		}

 	}

@@ -94,9 +96,35 @@ func TestCommandsTooManyArguments(t *testing.T) {

 			t.Fatalf("Error should be present for %s command", command.name)

 		}

-		expectedError := fmt.Sprintf("Bad input to %s, too many arguments", command.name)

+		expectedError := errTooManyArguments(command.name)

-		if err.Error() != expectedError {

+		if err.Error() != expectedError.Error() {

+			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)

+		}

+	}

+}

+

+func TestCommandseBlankNames(t *testing.T) {

+	bflags := &BFlags{}

+	config := &container.Config{}

+

+	b := &Builder{flags: bflags, runConfig: config, disableCommit: true}

+

+	commands := []commandWithFunction{

+		{"ENV", func(args []string) error { return env(b, args, nil, "") }},

+		{"LABEL", func(args []string) error { return label(b, args, nil, "") }},

+	}

+

+	for _, command := range commands {

+		err := command.function([]string{"", ""})

+

+		if err == nil {

+			t.Fatalf("Error should be present for %s command", command.name)

+		}

+

+		expectedError := errBlankCommandNames(command.name)

+

+		if err.Error() != expectedError.Error() {

 			t.Fatalf("Wrong error message for %s. Got: %s. Should be: %s", command.name, err.Error(), expectedError)

 		}

 	}

@@ -45,7 +45,7 @@ func initDispatchTestCases() []dispatchTestCase {

 		{

 			name:          "ARG two arguments",

 			dockerfile:    "ARG foo bar",

-			expectedError: "ARG requires exactly one argument definition",

+			expectedError: "ARG requires exactly one argument",

 			files:         nil,

 		},

 		{