azurerm_monitor_metric_alert - fix crash when `dynamic_criteria.0.i…

…gnore_data_before` isn't set (#21446)

internal/services/monitor/monitor_metric_alert_resource.go

@@ -647,14 +647,8 @@ func expandMonitorMetricAlertMultiResourceMultiMetricForDynamicMetricCriteria(in
 	for i, item := range input {
 		v := item.(map[string]interface{})
 		dimensions := expandMonitorMetricDimension(v["dimension"].([]interface{}))
-		var ignoreDataBefore *date.Time
-		if v := v["ignore_data_before"].(string); v != "" {
-			// Guaranteed in schema validation func.
-			t, _ := time.Parse(time.RFC3339, v)
-			ignoreDataBefore = &date.Time{Time: t}
-		}
 
-		criteria = append(criteria, metricalerts.DynamicMetricCriteria{
+		dynamicMetricCriteria := metricalerts.DynamicMetricCriteria{
 			Name:             fmt.Sprintf("Metric%d", i+1),
 			MetricNamespace:  utils.String(v["metric_namespace"].(string)),
 			MetricName:       v["metric_name"].(string),
@@ -666,9 +660,17 @@ func expandMonitorMetricAlertMultiResourceMultiMetricForDynamicMetricCriteria(in
 				NumberOfEvaluationPeriods: float64(v["evaluation_total_count"].(int)),
 				MinFailingPeriodsToAlert:  float64(v["evaluation_failure_count"].(int)),
 			},
-			IgnoreDataBefore:     pointer.To(ignoreDataBefore.String()),
 			SkipMetricValidation: utils.Bool(v["skip_metric_validation"].(bool)),
-		})
+		}
+
+		if datetime := v["ignore_data_before"].(string); datetime != "" {
+			// Guaranteed in schema validation func.
+			t, _ := time.Parse(time.RFC3339, datetime)
+			ignoreDataBefore := &date.Time{Time: t}
+			dynamicMetricCriteria.IgnoreDataBefore = pointer.To(ignoreDataBefore.String())
+		}
+
+		criteria = append(criteria, dynamicMetricCriteria)
 	}
 	return &metricalerts.MetricAlertMultipleResourceMultipleMetricCriteria{
 		AllOf: &criteria,

internal/services/monitor/monitor_metric_alert_resource_test.go

@@ -78,6 +78,21 @@ func TestAccMonitorMetricAlert_complete(t *testing.T) {
 	})
 }
 
+func TestAccMonitorMetricAlert_dynamicCriteria(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_monitor_metric_alert", "test")
+	r := MonitorMetricAlertResource{}
+
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.dynamicCriteria(data),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+	})
+}
+
 func TestAccMonitorMetricAlert_basicAndCompleteUpdate(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_monitor_metric_alert", "test")
 	r := MonitorMetricAlertResource{}
@@ -227,6 +242,50 @@ resource "azurerm_monitor_metric_alert" "import" {
 `, r.basic(data))
 }
 
+func (MonitorMetricAlertResource) dynamicCriteria(data acceptance.TestData) string {
+	return fmt.Sprintf(`
+provider "azurerm" {
+  features {}
+}
+
+resource "azurerm_resource_group" "test" {
+  name     = "acctestRG-%[1]d"
+  location = "%[2]s"
+}
+
+resource "azurerm_storage_account" "test" {
+  name                     = "acctestsa1%[3]s"
+  resource_group_name      = azurerm_resource_group.test.name
+  location                 = azurerm_resource_group.test.location
+  account_tier             = "Standard"
+  account_replication_type = "LRS"
+}
+
+resource "azurerm_monitor_metric_alert" "test" {
+  name                = "acctestMetricAlert-%[1]d"
+  resource_group_name = azurerm_resource_group.test.name
+  scopes              = [azurerm_storage_account.test.id]
+
+  dynamic_criteria {
+    metric_namespace  = "Microsoft.Storage/storageAccounts"
+    metric_name       = "Availability"
+    aggregation       = "Minimum"
+    operator          = "GreaterThan"
+    alert_sensitivity = "High"
+
+    dimension {
+      name     = "ApiName"
+      operator = "Include"
+      values   = ["*"]
+    }
+
+    evaluation_total_count   = 4
+    evaluation_failure_count = 1
+  }
+}
+`, data.RandomInteger, data.Locations.Primary, data.RandomString)
+}
+
 func (MonitorMetricAlertResource) multiCriteria(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 provider "azurerm" {