events/bus_policy: Fix diffs with policy

.changelog/22165.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_cloudwatch_event_bus_policy: Fix erroneous diffs in `policy` when no changes made or policies are equivalent
+```

internal/service/events/bus_policy.go

@@ -9,6 +9,7 @@ import (
 	"github.com/hashicorp/aws-sdk-go-base/tfawserr"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/structure"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
 	tfiam "github.com/hashicorp/terraform-provider-aws/internal/service/iam"
@@ -42,6 +43,10 @@ func ResourceBusPolicy() *schema.Resource {
 				Required:         true,
 				ValidateFunc:     validation.StringIsJSON,
 				DiffSuppressFunc: verify.SuppressEquivalentPolicyDiffs,
+				StateFunc: func(v interface{}) string {
+					json, _ := structure.NormalizeJsonString(v)
+					return json
+				},
 			},
 		},
 	}
@@ -51,15 +56,20 @@ func resourceBusPolicyCreate(d *schema.ResourceData, meta interface{}) error {
 	conn := meta.(*conns.AWSClient).EventsConn
 
 	eventBusName := d.Get("event_bus_name").(string)
-	policy := d.Get("policy").(string)
+
+	policy, err := structure.NormalizeJsonString(d.Get("policy").(string))
+
+	if err != nil {
+		return fmt.Errorf("policy (%s) is invalid JSON: %w", policy, err)
+	}
 
 	input := eventbridge.PutPermissionInput{
 		EventBusName: aws.String(eventBusName),
 		Policy:       aws.String(policy),
 	}
 
 	log.Printf("[DEBUG] Creating EventBridge policy: %s", input)
-	_, err := conn.PutPermission(&input)
+	_, err = conn.PutPermission(&input)
 	if err != nil {
 		return fmt.Errorf("Creating EventBridge policy failed: %w", err)
 	}
@@ -119,7 +129,13 @@ func resourceBusPolicyRead(d *schema.ResourceData, meta interface{}) error {
 	}
 	d.Set("event_bus_name", busName)
 
-	d.Set("policy", policy)
+	policyToSet, err := verify.PolicyToSet(d.Get("policy").(string), aws.StringValue(policy))
+
+	if err != nil {
+		return err
+	}
+
+	d.Set("policy", policyToSet)
 
 	return nil
 }
@@ -140,13 +156,19 @@ func resourceBusPolicyUpdate(d *schema.ResourceData, meta interface{}) error {
 
 	eventBusName := d.Id()
 
+	policy, err := structure.NormalizeJsonString(d.Get("policy").(string))
+
+	if err != nil {
+		return fmt.Errorf("policy (%s) is invalid JSON: %w", policy, err)
+	}
+
 	input := eventbridge.PutPermissionInput{
 		EventBusName: aws.String(eventBusName),
-		Policy:       aws.String(d.Get("policy").(string)),
+		Policy:       aws.String(policy),
 	}
 
 	log.Printf("[DEBUG] Update EventBridge Bus policy: %s", input)
-	_, err := conn.PutPermission(&input)
+	_, err = conn.PutPermission(&input)
 	if tfawserr.ErrMessageContains(err, eventbridge.ErrCodeResourceNotFoundException, "") {
 		log.Printf("[WARN] EventBridge Bus %q not found, removing from state", d.Id())
 		d.SetId("")

internal/service/events/bus_policy_test.go

@@ -1,13 +1,12 @@
 package events_test
 
 import (
-	"encoding/json"
 	"fmt"
-	"reflect"
 	"testing"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/eventbridge"
+	awspolicy "github.com/hashicorp/awspolicyequivalence"
 	sdkacctest "github.com/hashicorp/terraform-plugin-sdk/v2/helper/acctest"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
@@ -49,6 +48,31 @@ func TestAccEventsBusPolicy_basic(t *testing.T) {
 	})
 }
 
+func TestAccEventsBusPolicy_ignoreEquivalent(t *testing.T) {
+	resourceName := "aws_cloudwatch_event_bus_policy.test"
+	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { acctest.PreCheck(t) },
+		ErrorCheck:   acctest.ErrorCheck(t, eventbridge.EndpointsID),
+		Providers:    acctest.Providers,
+		CheckDestroy: testAccCheckBusDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccBusPolicyOrderConfig(rName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckBusPolicyExists(resourceName),
+					testAccBusPolicyDocument(resourceName),
+				),
+			},
+			{
+				Config:   testAccBusPolicyNewOrderConfig(rName),
+				PlanOnly: true,
+			},
+		},
+	})
+}
+
 func TestAccEventsBusPolicy_disappears(t *testing.T) {
 	resourceName := "aws_cloudwatch_event_bus_policy.test"
 	rstring := sdkacctest.RandString(5)
@@ -113,12 +137,6 @@ func testAccBusPolicyDocument(pr string) resource.TestCheckFunc {
 			return fmt.Errorf("No ID is set")
 		}
 
-		var eventBusPolicyResourcePolicyDocument map[string]interface{}
-		err := json.Unmarshal([]byte(eventBusPolicyResource.Primary.Attributes["policy"]), &eventBusPolicyResourcePolicyDocument)
-		if err != nil {
-			return fmt.Errorf("Parsing EventBridge bus policy for '%s' failed: %w", pr, err)
-		}
-
 		eventBusName := eventBusPolicyResource.Primary.ID
 
 		input := &eventbridge.DescribeEventBusInput{
@@ -131,18 +149,12 @@ func testAccBusPolicyDocument(pr string) resource.TestCheckFunc {
 			return fmt.Errorf("Reading EventBridge bus policy for '%s' failed: %w", pr, err)
 		}
 
-		var describedEventBusPolicy map[string]interface{}
-		err = json.Unmarshal([]byte(*describedEventBus.Policy), &describedEventBusPolicy)
-
-		if err != nil {
-			return fmt.Errorf("Reading EventBridge bus policy for '%s' failed: %w", pr, err)
-		}
 		if describedEventBus.Policy == nil || len(*describedEventBus.Policy) == 0 {
 			return fmt.Errorf("Not found: %s", pr)
 		}
 
-		if !reflect.DeepEqual(describedEventBusPolicy, eventBusPolicyResourcePolicyDocument) {
-			return fmt.Errorf("EventBridge bus policy mismatch for '%s'", pr)
+		if equivalent, err := awspolicy.PoliciesAreEquivalent(eventBusPolicyResource.Primary.Attributes["policy"], aws.StringValue(describedEventBus.Policy)); err != nil || !equivalent {
+			return fmt.Errorf("EventBridge bus policy not equivalent for '%s'", pr)
 		}
 
 		return nil
@@ -223,3 +235,71 @@ resource "aws_cloudwatch_event_bus_policy" "test" {
 }
 `, name)
 }
+
+func testAccBusPolicyOrderConfig(rName string) string {
+	return fmt.Sprintf(`
+resource "aws_cloudwatch_event_bus" "test" {
+  name = %[1]q
+}
+
+resource "aws_cloudwatch_event_bus_policy" "test" {
+  event_bus_name = aws_cloudwatch_event_bus.test.name
+
+  policy = jsonencode({
+    Statement = [{
+      Sid = %[1]q
+      Action = [
+        "events:PutEvents",
+        "events:PutRule",
+        "events:ListRules",
+        "events:DescribeRule",
+      ]
+      Effect = "Allow"
+      Principal = {
+        Service = [
+          "ecs.amazonaws.com",
+        ]
+      }
+      Resource = [
+        aws_cloudwatch_event_bus.test.arn,
+      ]
+    }]
+    Version = "2012-10-17"
+  })
+}
+`, rName)
+}
+
+func testAccBusPolicyNewOrderConfig(rName string) string {
+	return fmt.Sprintf(`
+resource "aws_cloudwatch_event_bus" "test" {
+  name = %[1]q
+}
+
+resource "aws_cloudwatch_event_bus_policy" "test" {
+  event_bus_name = aws_cloudwatch_event_bus.test.name
+
+  policy = jsonencode({
+    Statement = [{
+      Sid = %[1]q
+      Action = [
+        "events:PutRule",
+        "events:DescribeRule",
+        "events:PutEvents",
+        "events:ListRules",
+      ]
+      Effect = "Allow"
+      Principal = {
+        Service = [
+          "ecs.amazonaws.com",
+        ]
+      }
+      Resource = [
+        aws_cloudwatch_event_bus.test.arn,
+      ]
+    }]
+    Version = "2012-10-17"
+  })
+}
+`, rName)
+}