Restore build args after optimize. Fixes GoogleContainerTools#1910, G…

…oogleContainerTools#1912.

pkg/dockerfile/buildargs.go

@@ -17,6 +17,7 @@ limitations under the License.
 package dockerfile
 
 import (
+	"sort"
 	"strings"
 
 	d "github.com/docker/docker/builder/dockerfile"
@@ -51,8 +52,13 @@ func (b *BuildArgs) Clone() *BuildArgs {
 
 // ReplacementEnvs returns a list of filtered environment variables
 func (b *BuildArgs) ReplacementEnvs(envs []string) []string {
+	// Ensure that we operate on a new array and do not modify the underlying array
+	resultEnv := make([]string, len(envs))
+	copy(resultEnv, envs)
 	filtered := b.FilterAllowed(envs)
-	return append(envs, filtered...)
+	resultEnv = append(resultEnv, filtered...)
+	sort.Strings(resultEnv)
+	return resultEnv
 }
 
 // AddMetaArgs adds the supplied args map to b's allowedMetaArgs

pkg/executor/build.go

@@ -227,6 +227,11 @@ func (s *stageBuilder) optimize(compositeKey CompositeCache, cfg v1.Config) erro
 	if !s.opts.Cache {
 		return nil
 	}
+	var buildArgs = s.args.Clone()
+	// Restore build args back to their original values
+	defer func() {
+		s.args = buildArgs
+	}()
 
 	stopCache := false
 	// Possibly replace commands with their cached implementations.