Merge pull request #19226 from hashicorp/jbardin/no-diff

prefer prior state when there is no plan diff

builtin/providers/test/provider.go

@@ -21,6 +21,7 @@ func Provider() terraform.ResourceProvider {
 			"test_resource_gh12183":          testResourceGH12183(),
 			"test_resource_with_custom_diff": testResourceCustomDiff(),
 			"test_resource_timeout":          testResourceTimeout(),
+			"test_resource_diff_suppress":    testResourceDiffSuppress(),
 		},
 		DataSourcesMap: map[string]*schema.Resource{
 			"test_data_source":    testDataSource(),

builtin/providers/test/resource_diff_suppress.go

@@ -0,0 +1,57 @@
+package test
+
+import (
+	"strings"
+
+	"github.com/hashicorp/terraform/helper/schema"
+)
+
+func testResourceDiffSuppress() *schema.Resource {
+	return &schema.Resource{
+		Create: testResourceDiffSuppressCreate,
+		Read:   testResourceDiffSuppressRead,
+		Update: testResourceDiffSuppressUpdate,
+		Delete: testResourceDiffSuppressDelete,
+
+		Importer: &schema.ResourceImporter{
+			State: schema.ImportStatePassthrough,
+		},
+
+		Schema: map[string]*schema.Schema{
+			"val_to_upper": {
+				Type:     schema.TypeString,
+				Required: true,
+				ForceNew: true,
+				StateFunc: func(val interface{}) string {
+					return strings.ToUpper(val.(string))
+				},
+				DiffSuppressFunc: func(k, old, new string, d *schema.ResourceData) bool {
+					return strings.ToUpper(old) == strings.ToUpper(new)
+				},
+			},
+			"optional": {
+				Type:     schema.TypeString,
+				Optional: true,
+			},
+		},
+	}
+}
+
+func testResourceDiffSuppressCreate(d *schema.ResourceData, meta interface{}) error {
+	d.SetId("testId")
+
+	return testResourceRead(d, meta)
+}
+
+func testResourceDiffSuppressRead(d *schema.ResourceData, meta interface{}) error {
+	return nil
+}
+
+func testResourceDiffSuppressUpdate(d *schema.ResourceData, meta interface{}) error {
+	return nil
+}
+
+func testResourceDiffSuppressDelete(d *schema.ResourceData, meta interface{}) error {
+	d.SetId("")
+	return nil
+}

builtin/providers/test/resource_diff_suppress_test.go

@@ -0,0 +1,47 @@
+package test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/terraform/helper/resource"
+)
+
+func TestResourceDiffSuppress_create(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckResourceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_diff_suppress" "foo" {
+	val_to_upper = "foo"
+}
+				`),
+			},
+		},
+	})
+}
+func TestResourceDiffSuppress_update(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckResourceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_diff_suppress" "foo" {
+	val_to_upper = "foo"
+}
+				`),
+			},
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_diff_suppress" "foo" {
+	val_to_upper = "bar"
+	optional = "more"
+}
+				`),
+			},
+		},
+	})
+}

helper/plugin/grpc_provider.go

@@ -476,11 +476,16 @@ func (s *GRPCProviderServer) PlanResourceChange(_ context.Context, req *proto.Pl
 	}
 
 	if diff == nil {
-		// schema.Provider.Diff returns nil if it ends up making a diff with
-		// no changes, but our new interface wants us to return an actual
-		// change description that _shows_ there are no changes, so we return
-		// the proposed change that produces no diff.
-		resp.PlannedState = req.ProposedNewState
+		// schema.Provider.Diff returns nil if it ends up making a diff with no
+		// changes, but our new interface wants us to return an actual change
+		// description that _shows_ there are no changes. This is usually the
+		// PriorSate, however if there was no prior state and no diff, then we
+		// use the ProposedNewState.
+		if !priorStateVal.IsNull() {
+			resp.PlannedState = req.PriorState
+		} else {
+			resp.PlannedState = req.ProposedNewState
+		}
 		return resp, nil
 	}