command/format: fix missing elements at the end of lists in diffs

command/format/diff.go

@@ -1086,8 +1086,8 @@ func ctySequenceDiff(old, new []cty.Value) []*plans.Change {
 	var oldI, newI, lcsI int
 	for oldI < len(old) || newI < len(new) || lcsI < len(lcs) {
 		for oldI < len(old) && (lcsI >= len(lcs) || !old[oldI].RawEquals(lcs[lcsI])) {
-			isObjectDiff := old[oldI].Type().IsObjectType() && (newI >= len(new) || new[newI].Type().IsObjectType())
-			if isObjectDiff && newI < len(new) {
+			isObjectDiff := old[oldI].Type().IsObjectType() && newI < len(new) && new[newI].Type().IsObjectType() && (lcsI >= len(lcs) || !new[newI].RawEquals(lcs[lcsI]))
+			if isObjectDiff {
 				ret = append(ret, &plans.Change{
 					Action: plans.Update,
 					Before: old[oldI],

command/format/diff_test.go

@@ -888,11 +888,11 @@ func TestResourceChange_JSON(t *testing.T) {
 			Mode:   addrs.ManagedResourceMode,
 			Before: cty.ObjectVal(map[string]cty.Value{
 				"id":         cty.StringVal("i-02ae66f368e8518a9"),
-				"json_field": cty.StringVal(`[{"one": "111"}, {"two": "222"}]`),
+				"json_field": cty.StringVal(`[{"one": "111"}, {"two": "222"}, {"three": "333"}]`),
 			}),
 			After: cty.ObjectVal(map[string]cty.Value{
 				"id":         cty.UnknownVal(cty.String),
-				"json_field": cty.StringVal(`[{"one": "111"}]`),
+				"json_field": cty.StringVal(`[{"one": "111"}, {"three": "333"}]`),
 			}),
 			Schema: &configschema.Block{
 				Attributes: map[string]*configschema.Attribute{
@@ -913,6 +913,9 @@ func TestResourceChange_JSON(t *testing.T) {
               - {
                   - two = "222"
                 },
+                {
+                    three = "333"
+                },
             ]
         )
     }