evaluator: ensure entrypoint stays blank if set blank while CMD is set.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)

builder/dispatchers.go

@@ -255,11 +255,9 @@ func cmd(b *Builder, args []string, attributes map[string]bool) error {
 func entrypoint(b *Builder, args []string, attributes map[string]bool) error {
 	b.Config.Entrypoint = handleJsonArgs(args, attributes)
 
-	if len(b.Config.Entrypoint) == 0 {
+	if len(b.Config.Entrypoint) == 0 && len(b.Config.Cmd) == 0 {
 		b.Config.Entrypoint = []string{"/bin/sh", "-c"}
-	}
-
-	if !b.cmdSet {
+	} else if !b.cmdSet {
 		b.Config.Cmd = nil
 	}
 

integration-cli/docker_cli_build_test.go

@@ -791,6 +791,25 @@ func TestBuildEntrypoint(t *testing.T) {
 	if res != expected {
 		t.Fatalf("Entrypoint %s, expected %s", res, expected)
 	}
+
+	deleteImages(name)
+	expected = "[]"
+
+	_, err = buildImage(name,
+		`FROM busybox
+        ENTRYPOINT []`,
+		true)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res, err = inspectField(name, "Config.Entrypoint")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res != expected {
+		t.Fatalf("Entrypoint %s, expected %s", res, expected)
+	}
+
 	logDone("build - entrypoint")
 }