Specify fields on engine diff

pkg/resource/deploy/step_generator.go

@@ -1132,11 +1132,7 @@ func diffResource(urn resource.URN, id resource.ID, oldInputs, oldOutputs,
 		return diff, err
 	}
 	if diff.Changes == plugin.DiffUnknown {
-		if oldInputs.DeepEquals(newInputs) {
-			diff.Changes = plugin.DiffNone
-		} else {
-			diff.Changes = plugin.DiffSome
-		}
+		diff = plugin.NewDiffResultFromObjectDiff(oldInputs.Diff(newInputs))
 	}
 	return diff, nil
 }

sdk/go/common/resource/plugin/provider.go

@@ -217,6 +217,27 @@ type DiffResult struct {
 	DeleteBeforeReplace bool                    // if true, this resource must be deleted before recreating it.
 }
 
+// Transforms a `ObjectDiff` into an equivalent `DiffResult`. Because ObjectDiff has no way of
+// determining what should be changed vs replaced, all operations are added to the ChangedKeys set.
+func NewDiffResultFromObjectDiff(obj *resource.ObjectDiff) DiffResult {
+	result := DiffResult{}
+	if !obj.AnyChanges() {
+		result.Changes = DiffNone
+		return result
+	}
+
+	result.Changes = DiffSome
+	for _, k := range obj.Keys() {
+		if obj.Changed(k) {
+			result.ChangedKeys = append(result.ChangedKeys, k)
+		} else {
+			result.StableKeys = append(result.StableKeys, k)
+		}
+	}
+
+	return result
+}
+
 // Replace returns true if this diff represents a replacement.
 func (r DiffResult) Replace() bool {
 	for _, v := range r.DetailedDiff {

sdk/go/common/resource/properties_diff.go

@@ -55,6 +55,12 @@ func (diff *ObjectDiff) Same(k PropertyKey) bool {
 	return !diff.Changed(k)
 }
 
+// Returns true if there are no changes (adds, deletes, updates) in the diff. Also returns true if
+// diff is nil. Otherwise returns false.
+func (diff *ObjectDiff) AnyChanges() bool {
+	return diff != nil && len(diff.Adds)+len(diff.Deletes)+len(diff.Updates) > 0
+}
+
 // Keys returns a stable snapshot of all keys known to this object, across adds, deletes, sames, and updates.
 func (diff *ObjectDiff) Keys() []PropertyKey {
 	var ks []PropertyKey