@@ -3,6 +3,7 @@ package dockerfile

 import (

 	"fmt"

 	"github.com/docker/docker/runconfig/opts"

+	"io"

 )

 // builtinAllowedBuildArgs is list of built-in allowed build args

@@ -40,16 +41,20 @@ func newBuildArgs(argsFromOptions map[string]*string) *buildArgs {

 	}

 }

-// UnreferencedOptionArgs returns the list of args that were set from options but

-// were never referenced from the Dockerfile

-func (b *buildArgs) UnreferencedOptionArgs() []string {

+// WarnOnUnusedBuildArgs checks if there are any leftover build-args that were

+// passed but not consumed during build. Print a warning, if there are any.

+func (b *buildArgs) WarnOnUnusedBuildArgs(out io.Writer) {

 	leftoverArgs := []string{}

 	for arg := range b.argsFromOptions {

-		if _, ok := b.referencedArgs[arg]; !ok {

+		_, isReferenced := b.referencedArgs[arg]

+		_, isBuiltin := builtinAllowedBuildArgs[arg]

+		if !isBuiltin && !isReferenced {

 			leftoverArgs = append(leftoverArgs, arg)

 		}

 	}

-	return leftoverArgs

+	if len(leftoverArgs) > 0 {

+		fmt.Fprintf(out, "[Warning] One or more build-args %v were not consumed\n", leftoverArgs)

+	}

 }

 // ResetAllowed clears the list of args that are allowed to be used by a

@@ -69,13 +74,13 @@ func (b *buildArgs) AddArg(key string, value *string) {

 	b.referencedArgs[key] = struct{}{}

 }

-// IsUnreferencedBuiltin checks if the key is a built-in arg, or if it has been

-// referenced by the Dockerfile. Returns true if the arg is a builtin that has

-// not been referenced in the Dockerfile.

-func (b *buildArgs) IsUnreferencedBuiltin(key string) bool {

+// IsReferencedOrNotBuiltin checks if the key is a built-in arg, or if it has been

+// referenced by the Dockerfile. Returns true if the arg is not a builtin or

+// if the builtin has been referenced in the Dockerfile.

+func (b *buildArgs) IsReferencedOrNotBuiltin(key string) bool {

 	_, isBuiltin := builtinAllowedBuildArgs[key]

 	_, isAllowed := b.allowedBuildArgs[key]

-	return isBuiltin && !isAllowed

+	return isAllowed || !isBuiltin

 }

 // GetAllAllowed returns a mapping with all the allowed args

@@ -3,6 +3,7 @@ package dockerfile

 import (

 	"testing"

+	"bytes"

 	"github.com/stretchr/testify/assert"

 )

@@ -62,3 +63,38 @@ func TestGetAllMeta(t *testing.T) {

 	}

 	assert.Equal(t, expected, all)

 }

+

+func TestWarnOnUnusedBuildArgs(t *testing.T) {

+	buildArgs := newBuildArgs(map[string]*string{

+		"ThisArgIsUsed":    strPtr("fromopt1"),

+		"ThisArgIsNotUsed": strPtr("fromopt2"),

+		"HTTPS_PROXY":      strPtr("referenced builtin"),

+		"HTTP_PROXY":       strPtr("unreferenced builtin"),

+	})

+	buildArgs.AddArg("ThisArgIsUsed", nil)

+	buildArgs.AddArg("HTTPS_PROXY", nil)

+

+	buffer := new(bytes.Buffer)

+	buildArgs.WarnOnUnusedBuildArgs(buffer)

+	out := buffer.String()

+	assert.NotContains(t, out, "ThisArgIsUsed")

+	assert.NotContains(t, out, "HTTPS_PROXY")

+	assert.NotContains(t, out, "HTTP_PROXY")

+	assert.Contains(t, out, "ThisArgIsNotUsed")

+}

+

+func TestIsUnreferencedBuiltin(t *testing.T) {

+	buildArgs := newBuildArgs(map[string]*string{

+		"ThisArgIsUsed":    strPtr("fromopt1"),

+		"ThisArgIsNotUsed": strPtr("fromopt2"),

+		"HTTPS_PROXY":      strPtr("referenced builtin"),

+		"HTTP_PROXY":       strPtr("unreferenced builtin"),

+	})

+	buildArgs.AddArg("ThisArgIsUsed", nil)

+	buildArgs.AddArg("HTTPS_PROXY", nil)

+

+	assert.True(t, buildArgs.IsReferencedOrNotBuiltin("ThisArgIsUsed"))

+	assert.True(t, buildArgs.IsReferencedOrNotBuiltin("ThisArgIsNotUsed"))

+	assert.True(t, buildArgs.IsReferencedOrNotBuiltin("HTTPS_PROXY"))

+	assert.False(t, buildArgs.IsReferencedOrNotBuiltin("HTTP_PROXY"))

+}

@@ -156,7 +156,7 @@ func (b *Builder) build(source builder.Source, dockerfile *parser.Result) (*buil

 		return nil, errors.Errorf("failed to reach build target %s in Dockerfile", b.options.Target)

 	}

-	b.warnOnUnusedBuildArgs()

+	b.buildArgs.WarnOnUnusedBuildArgs(b.Stderr)

 	if dispatchState.imageID == "" {

 		return nil, errors.New("No image was generated. Is your Dockerfile empty?")

@@ -235,15 +235,6 @@ func addNodesForLabelOption(dockerfile *parser.Node, labels map[string]string) {

 	dockerfile.Children = append(dockerfile.Children, node)

 }

-// check if there are any leftover build-args that were passed but not

-// consumed during build. Print a warning, if there are any.

-func (b *Builder) warnOnUnusedBuildArgs() {

-	leftoverArgs := b.buildArgs.UnreferencedOptionArgs()

-	if len(leftoverArgs) > 0 {

-		fmt.Fprintf(b.Stderr, "[Warning] One or more build-args %v were not consumed\n", leftoverArgs)

-	}

-}

-

 // BuildFromConfig builds directly from `changes`, treating it as if it were the contents of a Dockerfile

 // It will:

 // - Call parse.Parse() to get an AST root for the concatenated Dockerfile entries.

@@ -416,7 +416,7 @@ func prependEnvOnCmd(buildArgs *buildArgs, buildArgVars []string, cmd strslice.S

 	var tmpBuildEnv []string

 	for _, env := range buildArgVars {

 		key := strings.SplitN(env, "=", 2)[0]

-		if !buildArgs.IsUnreferencedBuiltin(key) {

+		if buildArgs.IsReferencedOrNotBuiltin(key) {

 			tmpBuildEnv = append(tmpBuildEnv, env)

 		}

 	}