Ephemeral write only attributes (#3171)

Signed-off-by: Andrei Ciobanu <andrei.ciobanu@opentofu.org>
Signed-off-by: Christian Mesh <christianmesh1@gmail.com>

internal/command/jsonformat/differ/attribute.go

@@ -6,7 +6,9 @@
 package differ
 
 import (
+	"github.com/opentofu/opentofu/internal/command/jsonformat/computed/renderers"
 	"github.com/opentofu/opentofu/internal/command/jsonformat/structured"
+	"github.com/opentofu/opentofu/internal/plans"
 	"github.com/zclconf/go-cty/cty"
 	ctyjson "github.com/zclconf/go-cty/cty/json"
 
@@ -15,7 +17,20 @@ import (
 	"github.com/opentofu/opentofu/internal/command/jsonprovider"
 )
 
-func ComputeDiffForAttribute(change structured.Change, attribute *jsonprovider.Attribute) computed.Diff {
+// ComputeDiffForAttribute generates the diff for the change.
+// It handles 3 specific cases:
+//   - When the attribute for which the change is generated is a nested object,
+//     it generates the diff for each attribute
+//     of the nested object.
+//   - If the attribute is write-only, due to the fact that its changes will always be null, we want
+//     to return a diff with the same action as the parent's.
+//     If we use change.CalculateAction(), then the action will always be NoOp because of the
+//     which will skip from showing this in the diff.
+//   - If none above, it tries to generate the diff by using the specific generator for the attr type.
+func ComputeDiffForAttribute(change structured.Change, attribute *jsonprovider.Attribute, parentAction plans.Action) computed.Diff {
+	if attribute.WriteOnly {
+		return computeAttributeDiffAsWriteOnly(change, parentAction)
+	}
 	if attribute.AttributeNestedType != nil {
 		return computeDiffForNestedAttribute(change, attribute.AttributeNestedType)
 	}
@@ -87,3 +102,7 @@ func unmarshalAttribute(attribute *jsonprovider.Attribute) cty.Type {
 	}
 	return ctyType
 }
+
+func computeAttributeDiffAsWriteOnly(change structured.Change, parentAction plans.Action) computed.Diff {
+	return asDiffWithInheritedAction(change, parentAction, renderers.WriteOnly())
+}

internal/command/jsonformat/differ/block.go

@@ -49,7 +49,11 @@ func ComputeDiffForBlock(change structured.Change, block *jsonprovider.Block) co
 		childValue.BeforeExplicit = false
 		childValue.AfterExplicit = false
 
-		childChange := ComputeDiffForAttribute(childValue, attr)
+		// Because we want to print also the write-only attributes, we need to pass in the parent block
+		// action instead of the child one.
+		// This is because the child action will always result in NoOp since for write-only attributes, the
+		// values returned will be null.
+		childChange := ComputeDiffForAttribute(childValue, attr, current)
 		if childChange.Action == plans.NoOp && childValue.Before == nil && childValue.After == nil {
 			// Don't record nil values at all in blocks.
 			continue

internal/command/jsonformat/differ/differ.go

@@ -8,6 +8,7 @@ package differ
 import (
 	"github.com/opentofu/opentofu/internal/command/jsonformat/computed"
 	"github.com/opentofu/opentofu/internal/command/jsonformat/structured"
+	"github.com/opentofu/opentofu/internal/plans"
 )
 
 // asDiff is a helper function to abstract away some simple and common
@@ -15,3 +16,10 @@ import (
 func asDiff(change structured.Change, renderer computed.DiffRenderer) computed.Diff {
 	return computed.NewDiff(renderer, change.CalculateAction(), change.ReplacePaths.Matches())
 }
+
+// asDiffWithInheritedAction is a specific implementation of asDiff that gets also a parentAction plans.Action.
+// This is used when the given change is known to always generate a NoOp diff, but it still should be shown
+// in the printed diff.
+func asDiffWithInheritedAction(change structured.Change, parentAction plans.Action, renderer computed.DiffRenderer) computed.Diff {
+	return computed.NewDiff(renderer, parentAction, change.ReplacePaths.Matches())
+}

internal/command/jsonformat/differ/differ_test.go

@@ -101,6 +101,71 @@ func TestValue_SimpleBlocks(t *testing.T) {
 				"normal_attribute": renderers.ValidatePrimitive(nil, "some value", plans.Create, false),
 			}, nil, nil, nil, nil, plans.Create, false),
 		},
+
+		"delete_with_write_only_value": {
+			input: structured.Change{
+				Before:          map[string]any{},
+				After:           nil,
+				BeforeSensitive: false,
+				AfterSensitive:  false,
+			},
+			block: &jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_attribute": {
+						AttributeType: unmarshalType(t, cty.String),
+						WriteOnly:     true,
+					},
+				},
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_with_write_only": {
+						NestingMode: "single",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"inner_write_only": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			validate: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_attribute": renderers.ValidateWriteOnly(plans.Delete, false),
+			}, nil, nil, nil, nil, plans.Delete, false),
+		},
+		"create_with_write_only_value": {
+			input: structured.Change{
+				Before:          nil,
+				After:           map[string]any{},
+				BeforeSensitive: false,
+				AfterSensitive:  false,
+			},
+			block: &jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_attribute": {
+						AttributeType: unmarshalType(t, cty.String),
+						WriteOnly:     true,
+					},
+				},
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_with_write_only": {
+						NestingMode: "single",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"inner_write_only": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			validate: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_attribute": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
 	}
 	for name, tc := range tcs {
 		// Set some default values
@@ -746,17 +811,17 @@ func TestValue_ObjectAttributes(t *testing.T) {
 				}
 
 				if tc.validateObject != nil {
-					tc.validateObject(t, ComputeDiffForAttribute(tc.input, attribute))
+					tc.validateObject(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 					return
 				}
 
 				if tc.validateSingleDiff != nil {
-					tc.validateSingleDiff(t, ComputeDiffForAttribute(tc.input, attribute))
+					tc.validateSingleDiff(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateObject(tc.validateDiffs, tc.validateAction, tc.validateReplace)
-				validate(t, ComputeDiffForAttribute(tc.input, attribute))
+				validate(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 			})
 
 			t.Run("map", func(t *testing.T) {
@@ -770,7 +835,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 						"element": tc.validateObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -778,14 +843,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 						"element": tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 					"element": renderers.ValidateObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("list", func(t *testing.T) {
@@ -796,7 +861,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 				input := wrapChangeInSlice(tc.input)
 
 				if tc.validateList != nil {
-					tc.validateList(t, ComputeDiffForAttribute(input, attribute))
+					tc.validateList(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -804,7 +869,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateList([]renderers.ValidateDiffFunction{
 						tc.validateObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -812,14 +877,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateList([]renderers.ValidateDiffFunction{
 						tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateList([]renderers.ValidateDiffFunction{
 					renderers.ValidateObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("set", func(t *testing.T) {
@@ -836,7 +901,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 						ret = append(ret, tc.validateSetDiffs.After.Validate(renderers.ValidateObject))
 						return ret
 					}(), collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -844,7 +909,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 						tc.validateObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -852,14 +917,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 						tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 					renderers.ValidateObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 		})
 
@@ -881,17 +946,17 @@ func TestValue_ObjectAttributes(t *testing.T) {
 				}
 
 				if tc.validateNestedObject != nil {
-					tc.validateNestedObject(t, ComputeDiffForAttribute(tc.input, attribute))
+					tc.validateNestedObject(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 					return
 				}
 
 				if tc.validateSingleDiff != nil {
-					tc.validateSingleDiff(t, ComputeDiffForAttribute(tc.input, attribute))
+					tc.validateSingleDiff(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateNestedObject(tc.validateDiffs, tc.validateAction, tc.validateReplace)
-				validate(t, ComputeDiffForAttribute(tc.input, attribute))
+				validate(t, ComputeDiffForAttribute(tc.input, attribute, tc.input.CalculateAction()))
 			})
 
 			t.Run("map", func(t *testing.T) {
@@ -916,7 +981,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 						"element": tc.validateNestedObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -924,14 +989,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 						"element": tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 					"element": renderers.ValidateNestedObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("list", func(t *testing.T) {
@@ -956,7 +1021,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateNestedList([]renderers.ValidateDiffFunction{
 						tc.validateNestedObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -964,14 +1029,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateNestedList([]renderers.ValidateDiffFunction{
 						tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateNestedList([]renderers.ValidateDiffFunction{
 					renderers.ValidateNestedObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("set", func(t *testing.T) {
@@ -999,7 +1064,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 						ret = append(ret, tc.validateSetDiffs.After.Validate(renderers.ValidateNestedObject))
 						return ret
 					}(), collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -1007,7 +1072,7 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 						tc.validateNestedObject,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
@@ -1015,14 +1080,14 @@ func TestValue_ObjectAttributes(t *testing.T) {
 					validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 						tc.validateSingleDiff,
 					}, collectionDefaultAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 					renderers.ValidateNestedObject(tc.validateDiffs, tc.validateAction, tc.validateReplace),
 				}, collectionDefaultAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 		})
 	}
@@ -1840,9 +1905,9 @@ func TestValue_PrimitiveAttributes(t *testing.T) {
 
 		t.Run(name, func(t *testing.T) {
 			t.Run("direct", func(t *testing.T) {
-				tc.validateDiff(t, ComputeDiffForAttribute(tc.input, &jsonprovider.Attribute{
-					AttributeType: unmarshalType(t, tc.attribute),
-				}))
+				attr := &jsonprovider.Attribute{AttributeType: unmarshalType(t, tc.attribute)}
+				diff := ComputeDiffForAttribute(tc.input, attr, tc.input.CalculateAction())
+				tc.validateDiff(t, diff)
 			})
 
 			t.Run("map", func(t *testing.T) {
@@ -1854,7 +1919,7 @@ func TestValue_PrimitiveAttributes(t *testing.T) {
 				validate := renderers.ValidateMap(map[string]renderers.ValidateDiffFunction{
 					"element": tc.validateDiff,
 				}, defaultCollectionsAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("list", func(t *testing.T) {
@@ -1865,14 +1930,14 @@ func TestValue_PrimitiveAttributes(t *testing.T) {
 
 				if tc.validateSliceDiffs != nil {
 					validate := renderers.ValidateList(tc.validateSliceDiffs, defaultCollectionsAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateList([]renderers.ValidateDiffFunction{
 					tc.validateDiff,
 				}, defaultCollectionsAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 
 			t.Run("set", func(t *testing.T) {
@@ -1883,14 +1948,14 @@ func TestValue_PrimitiveAttributes(t *testing.T) {
 
 				if tc.validateSliceDiffs != nil {
 					validate := renderers.ValidateSet(tc.validateSliceDiffs, defaultCollectionsAction, false)
-					validate(t, ComputeDiffForAttribute(input, attribute))
+					validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 					return
 				}
 
 				validate := renderers.ValidateSet([]renderers.ValidateDiffFunction{
 					tc.validateDiff,
 				}, defaultCollectionsAction, false)
-				validate(t, ComputeDiffForAttribute(input, attribute))
+				validate(t, ComputeDiffForAttribute(input, attribute, input.CalculateAction()))
 			})
 		})
 	}
@@ -2261,7 +2326,7 @@ func TestValue_CollectionAttributes(t *testing.T) {
 		}
 
 		t.Run(name, func(t *testing.T) {
-			tc.validateDiff(t, ComputeDiffForAttribute(tc.input, tc.attribute))
+			tc.validateDiff(t, ComputeDiffForAttribute(tc.input, tc.attribute, tc.input.CalculateAction()))
 		})
 	}
 }
@@ -3005,6 +3070,404 @@ func TestSpecificCases(t *testing.T) {
 	}
 }
 
+func TestWriteOnly_ComputeDiffForBlock(t *testing.T) {
+	// NOTE: The write-only change will *always* have the after change null.
+	// We set specific values in this test for the after change to ensure that,
+	// based on the attribute's schema, we use the correct renderers for these attributes.
+	cases := map[string]struct {
+		block     jsonprovider.Block
+		change    structured.Change
+		validator renderers.ValidateDiffFunction
+	}{
+		// ---> Attributes with basic types
+		// attributes with basic types
+		"write_only_primitive_attribute": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_attribute": {
+						AttributeType: unmarshalType(t, cty.String),
+						Optional:      true,
+						WriteOnly:     true,
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_attribute": "dummy value", // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_attribute": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
+		"write_only_list": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_list": {
+						AttributeType: unmarshalType(t, cty.List(cty.Object(map[string]cty.Type{"val": cty.String}))),
+						Optional:      true,
+						WriteOnly:     true,
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_list": []string{"val", "b"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_list": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
+		"write_only_set": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_set": {
+						AttributeType: unmarshalType(t, cty.Set(cty.Object(map[string]cty.Type{"val": cty.String}))),
+						Optional:      true,
+						WriteOnly:     true,
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_set": []string{"val", "b"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_set": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
+		"write_only_map": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_map": {
+						AttributeType: unmarshalType(t, cty.Map(cty.String)),
+						Optional:      true,
+						WriteOnly:     true,
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_map": map[string]string{"bar": "barv", "baz": "bazv"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_map": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
+		"write_only_object": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_obj": {
+						AttributeType: unmarshalType(t, cty.Object(map[string]cty.Type{"val": cty.String})),
+						Optional:      true,
+						WriteOnly:     true,
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_obj": map[string]string{"bar": "barv"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(map[string]renderers.ValidateDiffFunction{
+				"write_only_obj": renderers.ValidateWriteOnly(plans.Create, false),
+			}, nil, nil, nil, nil, plans.Create, false),
+		},
+		// ---> Attributes with nested types
+		"attribute_single_nested_contains_write_only_attribute": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_obj": {
+						AttributeNestedType: &jsonprovider.NestedType{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"val": {
+									AttributeType: unmarshalType(t, cty.Object(map[string]cty.Type{"val": cty.String})),
+									Optional:      true,
+									WriteOnly:     true,
+								},
+							},
+							NestingMode: "single",
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_obj": map[string]any{"val": "foo"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				map[string]renderers.ValidateDiffFunction{
+					"write_only_obj": renderers.ValidateNestedObject(
+						map[string]renderers.ValidateDiffFunction{
+							"val": renderers.ValidateWriteOnly(plans.Create, false),
+						},
+						plans.Create, false),
+				},
+				nil, nil, nil, nil, plans.Create, false),
+		},
+		"attribute_map_nested_contains_write_only_attribute": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_map": {
+						AttributeNestedType: &jsonprovider.NestedType{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"val": {
+									AttributeType: unmarshalType(t, cty.Object(map[string]cty.Type{"val": cty.String})),
+									Optional:      true,
+									WriteOnly:     true,
+								},
+							},
+							NestingMode: "map",
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_map": map[string]any{"val": "val value"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				map[string]renderers.ValidateDiffFunction{
+					"write_only_map": renderers.ValidateMap(
+						map[string]renderers.ValidateDiffFunction{
+							"val": renderers.ValidateNestedObject(
+								map[string]renderers.ValidateDiffFunction{
+									"val": renderers.ValidateWriteOnly(plans.Create, false),
+								},
+								plans.Create, false),
+						},
+						plans.Create, false),
+				},
+				nil, nil, nil, nil, plans.Create, false),
+		},
+		"attribute_list_nested_contains_write_only_attribute": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_list": {
+						AttributeNestedType: &jsonprovider.NestedType{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"val": {
+									AttributeType: unmarshalType(t, cty.Object(map[string]cty.Type{"val": cty.String})),
+									Optional:      true,
+									WriteOnly:     true,
+								},
+							},
+							NestingMode: "list",
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_list": []any{map[string]any{"val": "foo value"}}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				map[string]renderers.ValidateDiffFunction{
+					"write_only_list": renderers.ValidateNestedList(
+						[]renderers.ValidateDiffFunction{
+							renderers.ValidateNestedObject(
+								map[string]renderers.ValidateDiffFunction{
+									"val": renderers.ValidateWriteOnly(plans.Create, false),
+								},
+								plans.Create, false),
+						},
+						plans.Create, false),
+				},
+				nil, nil, nil, nil, plans.Create, false),
+		},
+		"attribute_set_nested_contains_write_only_attribute": {
+			block: jsonprovider.Block{
+				Attributes: map[string]*jsonprovider.Attribute{
+					"write_only_set": {
+						AttributeNestedType: &jsonprovider.NestedType{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"val": {
+									AttributeType: unmarshalType(t, cty.Object(map[string]cty.Type{"val": cty.String})),
+									Optional:      true,
+									WriteOnly:     true,
+								},
+							},
+							NestingMode: "set",
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"write_only_set": []any{map[string]any{"val": "foo value"}}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				map[string]renderers.ValidateDiffFunction{
+					"write_only_set": renderers.ValidateSet(
+						[]renderers.ValidateDiffFunction{
+							renderers.ValidateNestedObject(
+								map[string]renderers.ValidateDiffFunction{
+									"val": renderers.ValidateWriteOnly(plans.Create, false),
+								},
+								plans.Create, false),
+						},
+						plans.Create, false),
+				},
+				nil, nil, nil, nil, plans.Create, false),
+		},
+		// ---> Nested blocks
+		"single_nested_block": {
+			block: jsonprovider.Block{
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_block": {
+						NestingMode: "single",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"write_only_attr": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"nested_block": map[string]any{"write_only_attr": "foo"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				nil,
+				map[string]renderers.ValidateDiffFunction{
+					"nested_block": renderers.ValidateBlock(
+						map[string]renderers.ValidateDiffFunction{
+							"write_only_attr": renderers.ValidateWriteOnly(plans.Create, false),
+						},
+						nil, nil, nil, nil, plans.Create, false),
+				},
+				nil, nil, nil, plans.Create, false),
+		},
+		"map_nested_block": {
+			block: jsonprovider.Block{
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_block": {
+						NestingMode: "map",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"write_only_attr": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"nested_block": map[string]any{"write_only_attr": "foo"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				nil, nil, nil,
+				map[string]map[string]renderers.ValidateDiffFunction{
+					"nested_block": {
+						"write_only_attr": renderers.ValidateBlock(
+							map[string]renderers.ValidateDiffFunction{
+								"write_only_attr": renderers.ValidateWriteOnly(plans.Create, false),
+							},
+							nil, nil, nil, nil, plans.Create, false),
+					},
+				},
+				nil, plans.Create, false),
+		},
+		"list_nested_block": {
+			block: jsonprovider.Block{
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_block": {
+						NestingMode: "list",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"write_only_attr": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"nested_block": []any{"value"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				nil, nil,
+				map[string][]renderers.ValidateDiffFunction{
+					"nested_block": {
+						renderers.ValidateBlock(
+							map[string]renderers.ValidateDiffFunction{
+								"write_only_attr": renderers.ValidateWriteOnly(plans.Create, false),
+							},
+							nil, nil, nil, nil, plans.Create, false),
+					},
+				},
+				nil, nil, plans.Create, false),
+		},
+		"set_nested_block": {
+			block: jsonprovider.Block{
+				BlockTypes: map[string]*jsonprovider.BlockType{
+					"nested_block": {
+						NestingMode: "set",
+						Block: &jsonprovider.Block{
+							Attributes: map[string]*jsonprovider.Attribute{
+								"write_only_attr": {
+									AttributeType: unmarshalType(t, cty.String),
+									WriteOnly:     true,
+								},
+							},
+						},
+					},
+				},
+			},
+			change: structured.Change{
+				After: map[string]any{
+					"nested_block": []any{"value"}, // NOTE: since this is WO attr, IRL it's nil
+				},
+			},
+			validator: renderers.ValidateBlock(
+				nil, nil, nil, nil,
+				map[string][]renderers.ValidateDiffFunction{
+					"nested_block": {
+						renderers.ValidateBlock(
+							map[string]renderers.ValidateDiffFunction{
+								"write_only_attr": renderers.ValidateWriteOnly(plans.Create, false),
+							},
+							nil, nil, nil, nil, plans.Create, false),
+					},
+				}, plans.Create, false),
+		},
+	}
+
+	for name, tt := range cases {
+		t.Run(name, func(t *testing.T) {
+			if tt.change.ReplacePaths == nil {
+				tt.change.ReplacePaths = &attribute_path.PathMatcher{}
+			}
+			if tt.change.RelevantAttributes == nil {
+				tt.change.RelevantAttributes = attribute_path.AlwaysMatcher()
+
+			}
+			diff := ComputeDiffForBlock(tt.change, &tt.block)
+			tt.validator(t, diff)
+		})
+	}
+}
+
 // unmarshalType converts a cty.Type into a json.RawMessage understood by the
 // schema. It also lets the testing framework handle any errors to keep the API
 // clean.

internal/command/jsonformat/differ/object.go

@@ -17,15 +17,15 @@ import (
 )
 
 func computeAttributeDiffAsObject(change structured.Change, attributes map[string]cty.Type) computed.Diff {
-	attributeDiffs, action := processObject(change, attributes, func(value structured.Change, ctype cty.Type) computed.Diff {
+	attributeDiffs, action := processObject(change, attributes, func(value structured.Change, ctype cty.Type, _ plans.Action) computed.Diff {
 		return ComputeDiffForType(value, ctype)
 	})
 	return computed.NewDiff(renderers.Object(attributeDiffs), action, change.ReplacePaths.Matches())
 }
 
 func computeAttributeDiffAsNestedObject(change structured.Change, attributes map[string]*jsonprovider.Attribute) computed.Diff {
-	attributeDiffs, action := processObject(change, attributes, func(value structured.Change, attribute *jsonprovider.Attribute) computed.Diff {
-		return ComputeDiffForAttribute(value, attribute)
+	attributeDiffs, action := processObject(change, attributes, func(value structured.Change, attribute *jsonprovider.Attribute, parentAction plans.Action) computed.Diff {
+		return ComputeDiffForAttribute(value, attribute, parentAction)
 	})
 	return computed.NewDiff(renderers.NestedObject(attributeDiffs), action, change.ReplacePaths.Matches())
 }
@@ -41,7 +41,7 @@ func computeAttributeDiffAsNestedObject(change structured.Change, attributes map
 // Also, as it generic we cannot make this function a method on Change as you
 // can't create generic methods on structs. Instead, we make this a generic
 // function that receives the value as an argument.
-func processObject[T any](v structured.Change, attributes map[string]T, computeDiff func(structured.Change, T) computed.Diff) (map[string]computed.Diff, plans.Action) {
+func processObject[T any](v structured.Change, attributes map[string]T, computeDiff func(structured.Change, T, plans.Action) computed.Diff) (map[string]computed.Diff, plans.Action) {
 	attributeDiffs := make(map[string]computed.Diff)
 	mapValue := v.AsMap()
 
@@ -58,7 +58,7 @@ func processObject[T any](v structured.Change, attributes map[string]T, computeD
 		attributeValue.BeforeExplicit = false
 		attributeValue.AfterExplicit = false
 
-		attributeDiff := computeDiff(attributeValue, attribute)
+		attributeDiff := computeDiff(attributeValue, attribute, currentAction)
 		if attributeDiff.Action == plans.NoOp && attributeValue.Before == nil && attributeValue.After == nil {
 			// We skip attributes of objects that are null both before and
 			// after. We don't even count these as unchanged attributes.