Notification Policy: Fix perma-drift

Closes #1146

By switching from list to set, the order doesn't matter anymore

examples/resources/grafana_notification_policy/resource.tf

@@ -30,6 +30,16 @@ resource "grafana_notification_policy" "my_notification_policy" {
       match = "="
       value = "myvalue"
     }
+    matcher {
+      label = "alertname"
+      match = "="
+      value = "CPU Usage"
+    }
+    matcher {
+      label = "Name"
+      match = "=~"
+      value = "host.*|host-b.*"
+    }
     contact_point = grafana_contact_point.a_contact_point.name
     continue      = true
     mute_timings  = [grafana_mute_timing.a_mute_timing.name]

internal/resources/grafana/resource_alerting_notification_policy.go

@@ -105,7 +105,7 @@ func policySchema(depth uint) *schema.Resource {
 				},
 			},
 			"matcher": {
-				Type:        schema.TypeList,
+				Type:        schema.TypeSet,
 				Optional:    true,
 				Description: "Describes which labels this rule should match. When multiple matchers are supplied, an alert must match ALL matchers to be accepted by this policy. When no matchers are supplied, the rule will match all alert instances.",
 				Elem: &schema.Resource{
@@ -341,7 +341,7 @@ func unpackSpecificPolicy(p interface{}) (gapi.SpecificPolicy, error) {
 	}
 
 	if v, ok := json["matcher"]; ok && v != nil {
-		ms := v.([]interface{})
+		ms := v.(*schema.Set).List()
 		matchers := make([]gapi.Matcher, 0, len(ms))
 		for _, m := range ms {
 			matcher, err := unpackPolicyMatcher(m)

internal/resources/grafana/resource_alerting_notification_policy_test.go

@@ -35,9 +35,16 @@ func TestAccNotificationPolicy_basic(t *testing.T) {
 					// nested
 					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.#", "2"),
 					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.contact_point", "A Contact Point"),
-					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.label", "mylabel"),
-					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.match", "="),
-					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.value", "myvalue"),
+					// Matchers are reordered by the API
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.label", "Name"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.match", "=~"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.0.value", "host.*|host-b.*"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.1.label", "alertname"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.1.match", "="),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.1.value", "CPU Usage"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.2.label", "mylabel"),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.2.match", "="),
+					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.matcher.2.value", "myvalue"),
 					resource.TestCheckNoResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.group_by"),
 					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.continue", "true"),
 					resource.TestCheckResourceAttr("grafana_notification_policy.my_notification_policy", "policy.0.mute_timings.0", "Some Mute Timing"),