From fe117e9f02d25ba37e170829ed80e9bc44acd58b Mon Sep 17 00:00:00 2001
From: Radek Simko <radek.simko@gmail.com>
Date: Tue, 11 Dec 2018 12:56:11 +0000
Subject: [PATCH] command/format: Fix rendering of nested blocks during update

---
 command/format/diff.go      |  7 ++++-
 command/format/diff_test.go | 53 +++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/command/format/diff.go b/command/format/diff.go
index c58661663..37127e2d0 100644
--- a/command/format/diff.go
+++ b/command/format/diff.go
@@ -313,11 +313,16 @@ func (p *blockBodyDiffPrinter) writeNestedBlockDiffs(name string, blockS *config
 		if blankBefore && (len(oldItems) > 0 || len(newItems) > 0) {
 			p.buf.WriteRune('\n')
 		}
+
 		for i := 0; i < commonLen; i++ {
 			path := append(path, cty.IndexStep{Key: cty.NumberIntVal(int64(i))})
 			oldItem := oldItems[i]
 			newItem := newItems[i]
-			p.writeNestedBlockDiff(name, nil, &blockS.Block, plans.Update, oldItem, newItem, indent, path)
+			action := plans.Update
+			if oldItem.RawEquals(newItem) {
+				action = plans.NoOp
+			}
+			p.writeNestedBlockDiff(name, nil, &blockS.Block, action, oldItem, newItem, indent, path)
 		}
 		for i := commonLen; i < len(oldItems); i++ {
 			path := append(path, cty.IndexStep{Key: cty.NumberIntVal(int64(i))})
diff --git a/command/format/diff_test.go b/command/format/diff_test.go
index 1d7740d65..2dc002a8c 100644
--- a/command/format/diff_test.go
+++ b/command/format/diff_test.go
@@ -655,6 +655,59 @@ func TestResourceChange_map(t *testing.T) {
 
 func TestResourceChange_nestedList(t *testing.T) {
 	testCases := map[string]testCase{
+		"in-place update - equal": {
+			Action: plans.Update,
+			Mode:   addrs.ManagedResourceMode,
+			Before: cty.ObjectVal(map[string]cty.Value{
+				"id":  cty.StringVal("i-02ae66f368e8518a9"),
+				"ami": cty.StringVal("ami-BEFORE"),
+				"root_block_device": cty.ListVal([]cty.Value{
+					cty.ObjectVal(map[string]cty.Value{
+						"volume_type": cty.StringVal("gp2"),
+					}),
+				}),
+			}),
+			After: cty.ObjectVal(map[string]cty.Value{
+				"id":  cty.StringVal("i-02ae66f368e8518a9"),
+				"ami": cty.StringVal("ami-AFTER"),
+				"root_block_device": cty.ListVal([]cty.Value{
+					cty.ObjectVal(map[string]cty.Value{
+						"volume_type": cty.StringVal("gp2"),
+					}),
+				}),
+			}),
+			RequiredReplace: cty.NewPathSet(),
+			Schema: &configschema.Block{
+				Attributes: map[string]*configschema.Attribute{
+					"id":  {Type: cty.String, Optional: true, Computed: true},
+					"ami": {Type: cty.String, Optional: true},
+				},
+				BlockTypes: map[string]*configschema.NestedBlock{
+					"root_block_device": {
+						Block: configschema.Block{
+							Attributes: map[string]*configschema.Attribute{
+								"volume_type": {
+									Type:     cty.String,
+									Optional: true,
+									Computed: true,
+								},
+							},
+						},
+						Nesting: 2,
+					},
+				},
+			},
+			ExpectedOutput: `  # test_instance.example will be updated in-place
+  ~ resource "test_instance" "example" {
+      ~ ami = "ami-BEFORE" -> "ami-AFTER"
+        id  = "i-02ae66f368e8518a9"
+
+        root_block_device {
+            volume_type = "gp2"
+        }
+    }
+`,
+		},
 		"in-place update - creation": {
 			Action: plans.Update,
 			Mode:   addrs.ManagedResourceMode,