plan renderer: fix crash when updating a null attribute to unknown

Author: Liam Cervante

internal/command/jsonformat/computed/renderers/block.go

@@ -158,7 +158,7 @@ func (renderer blockRenderer) RenderHuman(diff computed.Diff, indent int, opts c
 			sort.Strings(keys)
 
 			if renderer.blocks.UnknownBlocks[key] {
-				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), plans.Create, false), "", opts)
+				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), diff.Action, false), "", opts)
 			}
 
 			for _, innerKey := range keys {
@@ -170,7 +170,7 @@ func (renderer blockRenderer) RenderHuman(diff computed.Diff, indent int, opts c
 			setOpts.ForceForcesReplacement = diff.Replace
 
 			if renderer.blocks.UnknownBlocks[key] {
-				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), plans.Create, false), "", opts)
+				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), diff.Action, false), "", opts)
 			}
 
 			for _, block := range renderer.blocks.SetBlocks[key] {
@@ -179,7 +179,7 @@ func (renderer blockRenderer) RenderHuman(diff computed.Diff, indent int, opts c
 		case renderer.blocks.IsListBlock(key):
 
 			if renderer.blocks.UnknownBlocks[key] {
-				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), plans.Create, false), "", opts)
+				renderBlock(computed.NewDiff(Unknown(computed.Diff{}), diff.Action, false), "", opts)
 			}
 
 			for _, block := range renderer.blocks.ListBlocks[key] {

internal/command/jsonformat/computed/renderers/renderer_test.go

@@ -433,6 +433,13 @@ jsonencode(
 			},
 			expected: "0 -> (known after apply)",
 		},
+		"computed_update_from_null": {
+			diff: computed.Diff{
+				Renderer: Unknown(computed.Diff{}),
+				Action:   plans.Update,
+			},
+			expected: "(known after apply)",
+		},
 		"computed_create_forces_replacement": {
 			diff: computed.Diff{
 				Renderer: Unknown(computed.Diff{}),

internal/command/jsonformat/computed/renderers/unknown.go

@@ -26,7 +26,12 @@ type unknownRenderer struct {
 }
 
 func (renderer unknownRenderer) RenderHuman(diff computed.Diff, indent int, opts computed.RenderHumanOpts) string {
-	if diff.Action == plans.Create {
+
+	// the before renderer can be nil and not a create action when the provider
+	// previously returned a null value for the computed attribute and is now
+	// declaring they will recompute it as part of the next update.
+
+	if diff.Action == plans.Create || renderer.before.Renderer == nil {
 		return fmt.Sprintf("(known after apply)%s", forcesReplacement(diff.Replace, opts))
 	}
 

internal/command/jsonformat/plan_test.go

@@ -3548,7 +3548,7 @@ func TestResourceChange_nestedList(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null
@@ -3607,7 +3607,7 @@ func TestResourceChange_nestedList(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null # forces replacement
@@ -4275,7 +4275,7 @@ func TestResourceChange_nestedSet(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null
@@ -4334,7 +4334,7 @@ func TestResourceChange_nestedSet(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null # forces replacement
@@ -4805,7 +4805,7 @@ func TestResourceChange_nestedMap(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device "gp1" {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null
@@ -4864,7 +4864,7 @@ func TestResourceChange_nestedMap(t *testing.T) {
         id    = "i-02ae66f368e8518a9"
         # (1 unchanged attribute hidden)
 
-      + root_block_device (known after apply)
+      ~ root_block_device (known after apply)
       - root_block_device "gp1" {
           - new_field   = "new_value" -> null
           - volume_type = "gp1" -> null # forces replacement