Allow Args to be used in Variable Evaluation

If the Dockerfile has a `ARG CHOWN_VAL=6173:6173`, then
a `COPY --chown=${CHOWN_VAL} srcFile destFile` will fail.
However if the Dockerfile has a `ENV CHOWN_VAL=6173:6173`
then it succeeds.

The dispatchCopy() and add() functions were only going through the
list of Environment variables to resolve a Variable instead
of the list of Args and Environment variables.

Now add the definitions from the ARG statements to the ones
from the ENV statements and use both when resolving
variables.

At some point I'd like to look into converting the b.Env to
a Map from a slice like b.Args, but didn't want to run this
down now.

Fixes: containers/buildah#2192
       and probably containers/buildah#2345

Signed-off-by: TomSweeneyRedHat <[email protected]>

dispatchers.go

@@ -153,8 +153,9 @@ func add(b *Builder, args []string, attributes map[string]bool, flagArgs []strin
 	var chown string
 	last := len(args) - 1
 	dest := makeAbsolute(args[last], b.RunConfig.WorkingDir)
+	userArgs := makeUserArgs(b)
 	for _, a := range flagArgs {
-		arg, err := ProcessWord(a, b.Env)
+		arg, err := ProcessWord(a, userArgs)
 		if err != nil {
 			return err
 		}
@@ -181,8 +182,9 @@ func dispatchCopy(b *Builder, args []string, attributes map[string]bool, flagArg
 	dest := makeAbsolute(args[last], b.RunConfig.WorkingDir)
 	var chown string
 	var from string
+	userArgs := makeUserArgs(b)
 	for _, a := range flagArgs {
-		arg, err := ProcessWord(a, b.Env)
+		arg, err := ProcessWord(a, userArgs)
 		if err != nil {
 			return err
 		}
@@ -649,3 +651,16 @@ func errTooManyArguments(command string) error {
 func errNotJSON(command string) error {
 	return fmt.Errorf("%s requires the arguments to be in JSON form", command)
 }
+
+// makeUserArgs - Package the variables from the Dockerfile defined by
+// the ENV aand the ARG statements into one slice so the values
+// defined by both can later be evaluated when resolving variables
+// such as ${MY_USER}
+func makeUserArgs(b *Builder) (userArgs []string) {
+
+	userArgs = b.Env
+	for key, value := range b.Args {
+		userArgs = append(userArgs, key+"="+value)
+	}
+	return userArgs
+}

dispatchers_test.go

@@ -177,6 +177,39 @@ func TestDispatchAddChownWithEnvironment(t *testing.T) {
 	}
 }
 
+func TestDispatchAddChownWithArg(t *testing.T) {
+	argsMap := make(map[string]string)
+	argsMap["CHOWN_VAL"] = "6731:6731"
+	mybuilder := Builder{
+		RunConfig: docker.Config{
+			WorkingDir: "/root",
+			Cmd:        []string{"/bin/sh"},
+			Image:      "alpine",
+		},
+		Args: argsMap,
+	}
+
+	args := []string{"/go/src/github.com/kubernetes-incubator/service-catalog/controller-manager", "."}
+	flagArgs := []string{"--chown=${CHOWN_VAL}"}
+	original := "ADD --chown=${CHOWN_VAL} /go/src/github.com/kubernetes-incubator/service-catalog/controller-manager ."
+	if err := add(&mybuilder, args, nil, flagArgs, original); err != nil {
+		t.Errorf("dispatchAdd error: %v", err)
+	}
+
+	expectedPendingCopies := []Copy{
+		{
+			From:     "",
+			Src:      []string{"/go/src/github.com/kubernetes-incubator/service-catalog/controller-manager"},
+			Dest:     "/root/", // destination must contain a trailing slash
+			Download: true,
+			Chown:    "6731:6731",
+		},
+	}
+	if !reflect.DeepEqual(mybuilder.PendingCopies, expectedPendingCopies) {
+		t.Errorf("Expected %v, to match %v\n", expectedPendingCopies, mybuilder.PendingCopies)
+	}
+}
+
 func TestDispatchCopyChownWithEnvironment(t *testing.T) {
 	mybuilder := Builder{
 		RunConfig: docker.Config{
@@ -208,6 +241,39 @@ func TestDispatchCopyChownWithEnvironment(t *testing.T) {
 	}
 }
 
+func TestDispatchCopyChownWithArg(t *testing.T) {
+	argsMap := make(map[string]string)
+	argsMap["CHOWN_VAL"] = "6731:6731"
+	mybuilder := Builder{
+		RunConfig: docker.Config{
+			WorkingDir: "/root",
+			Cmd:        []string{"/bin/sh"},
+			Image:      "alpine",
+		},
+		Args: argsMap,
+	}
+
+	args := []string{"/go/src/github.com/kubernetes-incubator/service-catalog/controller-manager", "."}
+	flagArgs := []string{"--chown=${CHOWN_VAL}"}
+	original := "COPY --chown=${CHOWN_VAL} /go/src/github.com/kubernetes-incubator/service-catalog/controller-manager ."
+	if err := dispatchCopy(&mybuilder, args, nil, flagArgs, original); err != nil {
+		t.Errorf("dispatchCopy error: %v", err)
+	}
+
+	expectedPendingCopies := []Copy{
+		{
+			From:     "",
+			Src:      []string{"/go/src/github.com/kubernetes-incubator/service-catalog/controller-manager"},
+			Dest:     "/root/", // destination must contain a trailing slash
+			Download: false,
+			Chown:    "6731:6731",
+		},
+	}
+	if !reflect.DeepEqual(mybuilder.PendingCopies, expectedPendingCopies) {
+		t.Errorf("Expected %v, to match %v\n", expectedPendingCopies, mybuilder.PendingCopies)
+	}
+}
+
 func TestDispatchAddChown(t *testing.T) {
 	mybuilder := Builder{
 		RunConfig: docker.Config{