5.0.0 - remove computed keys from JSON in monitoring dashboard

.changelog/9065.txt

@@ -0,0 +1,3 @@
+```release-note:breaking-change
+monitoring: fixed perma-diffs in `google_monitoring_dashboard.dashboard_json` by suppressing values returned by the API that are not in configuration
+```

google-beta/services/monitoring/resource_monitoring_dashboard.go

@@ -16,24 +16,45 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
 )
 
-func monitoringDashboardDiffSuppress(k, old, new string, d *schema.ResourceData) bool {
-	computedFields := []string{"etag", "name"}
+// This recursive function takes an old map and a new map and is intended to remove the computed keys
+// from the old json string (stored in state) so that it doesn't show a diff if it's not defined in the
+// new map's json string (defined in config)
+func removeComputedKeys(old map[string]interface{}, new map[string]interface{}) map[string]interface{} {
+	for k, v := range old {
+		if _, ok := old[k]; ok && new[k] == nil {
+			delete(old, k)
+			continue
+		}
+
+		if reflect.ValueOf(v).Kind() == reflect.Map {
+			old[k] = removeComputedKeys(v.(map[string]interface{}), new[k].(map[string]interface{}))
+			continue
+		}
+
+		if reflect.ValueOf(v).Kind() == reflect.Slice {
+			for i, j := range v.([]interface{}) {
+				if reflect.ValueOf(j).Kind() == reflect.Map {
+					old[k].([]interface{})[i] = removeComputedKeys(j.(map[string]interface{}), new[k].([]interface{})[i].(map[string]interface{}))
+				}
+			}
+			continue
+		}
+	}
+
+	return old
+}
 
+func monitoringDashboardDiffSuppress(k, old, new string, d *schema.ResourceData) bool {
 	oldMap, err := structure.ExpandJsonFromString(old)
 	if err != nil {
 		return false
 	}
-
 	newMap, err := structure.ExpandJsonFromString(new)
 	if err != nil {
 		return false
 	}
 
-	for _, f := range computedFields {
-		delete(oldMap, f)
-		delete(newMap, f)
-	}
-
+	oldMap = removeComputedKeys(oldMap, newMap)
 	return reflect.DeepEqual(oldMap, newMap)
 }
 

google-beta/services/monitoring/resource_monitoring_dashboard_test.go

@@ -85,8 +85,6 @@ func TestAccMonitoringDashboard_rowLayout(t *testing.T) {
 }
 
 func TestAccMonitoringDashboard_update(t *testing.T) {
-	// TODO: Fix requires a breaking change https://github.com/hashicorp/terraform-provider-google/issues/9976
-	t.Skip()
 	t.Parallel()
 
 	acctest.VcrTest(t, resource.TestCase{

website/docs/r/monitoring_dashboard.html.markdown

@@ -114,6 +114,12 @@ The following arguments are supported:
   The JSON representation of a dashboard, following the format at https://cloud.google.com/monitoring/api/ref_v3/rest/v1/projects.dashboards.
   The representation of an existing dashboard can be found by using the [API Explorer](https://cloud.google.com/monitoring/api/ref_v3/rest/v1/projects.dashboards/get)
 
+  ~> **Warning:** Because this is represented as a JSON string, Terraform doesn't have underlying information to know
+    which fields in the string have defaults. To prevent permanent diffs from default values, Terraform will attempt to
+    suppress diffs where the value is returned in the JSON string but doesn't exist in the configuration. Consequently,
+    legitmate remove-only diffs will also be suppressed. For Terraform to detect the diff, key removals must also be
+    accompanied by a non-removal change (trivial or not).
+
 - - -