command/push: ask for only variables that are unset

command/meta.go

@@ -170,6 +170,7 @@ func (m *Meta) InputMode() terraform.InputMode {
 	mode |= terraform.InputModeProvider
 	if len(m.variables) == 0 && m.autoKey == "" {
 		mode |= terraform.InputModeVar
+		mode |= terraform.InputModeVarUnset
 	}
 
 	return mode

command/push.go

@@ -84,6 +84,17 @@ func (c *PushCommand) Run(args []string) int {
 		return 1
 	}
 
+	// Get the variables we might already have
+	vars, err := c.client.Get("")
+	if err != nil {
+		c.Ui.Error(fmt.Sprintf(
+			"Error looking up prior pushed configuration: %s", err))
+		return 1
+	}
+	for k, v := range vars {
+		ctx.SetVariable(k, v)
+	}
+
 	// Ask for input
 	if err := ctx.Input(c.InputMode()); err != nil {
 		c.Ui.Error(fmt.Sprintf(
@@ -155,6 +166,7 @@ func (c *PushCommand) Synopsis() string {
 // pushClient is implementd internally to control where pushes go. This is
 // either to Atlas or a mock for testing.
 type pushClient interface {
+	Get(string) (map[string]string, error)
 	Upsert(*pushUpsertOptions) error
 }
 
@@ -166,11 +178,22 @@ type pushUpsertOptions struct {
 type mockPushClient struct {
 	File string
 
+	GetCalled bool
+	GetName   string
+	GetResult map[string]string
+	GetError  error
+
 	UpsertCalled  bool
 	UpsertOptions *pushUpsertOptions
 	UpsertError   error
 }
 
+func (c *mockPushClient) Get(name string) (map[string]string, error) {
+	c.GetCalled = true
+	c.GetName = name
+	return c.GetResult, c.GetError
+}
+
 func (c *mockPushClient) Upsert(opts *pushUpsertOptions) error {
 	f, err := os.Create(c.File)
 	if err != nil {

command/push_test.go

@@ -117,6 +117,61 @@ func TestPush_input(t *testing.T) {
 	}
 }
 
+func TestPush_inputPartial(t *testing.T) {
+	tmp, cwd := testCwd(t)
+	defer testFixCwd(t, tmp, cwd)
+
+	// Create remote state file, this should be pulled
+	conf, srv := testRemoteState(t, testState(), 200)
+	defer srv.Close()
+
+	// Persist local remote state
+	s := terraform.NewState()
+	s.Serial = 5
+	s.Remote = conf
+	testStateFileRemote(t, s)
+
+	// Path where the archive will be "uploaded" to
+	archivePath := testTempFile(t)
+	defer os.Remove(archivePath)
+
+	client := &mockPushClient{
+		File:      archivePath,
+		GetResult: map[string]string{"foo": "bar"},
+	}
+	ui := new(cli.MockUi)
+	c := &PushCommand{
+		Meta: Meta{
+			ContextOpts: testCtxConfig(testProvider()),
+			Ui:          ui,
+		},
+
+		client: client,
+	}
+
+	// Disable test mode so input would be asked and setup the
+	// input reader/writers.
+	test = false
+	defer func() { test = true }()
+	defaultInputReader = bytes.NewBufferString("foo\n")
+	defaultInputWriter = new(bytes.Buffer)
+
+	args := []string{
+		testFixturePath("push-input-partial"),
+	}
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	}
+
+	variables := map[string]string{
+		"foo": "bar",
+		"bar": "foo",
+	}
+	if !reflect.DeepEqual(client.UpsertOptions.Variables, variables) {
+		t.Fatalf("bad: %#v", client.UpsertOptions)
+	}
+}
+
 func TestPush_noState(t *testing.T) {
 	tmp, cwd := testCwd(t)
 	defer testFixCwd(t, tmp, cwd)

command/test-fixtures/push-input-partial/main.tf

@@ -0,0 +1,4 @@
+variable "foo" {}
+variable "bar" {}
+
+resource "test_instance" "foo" {}