From 4407d765a40f76cdbbc3552192d98ebcbcb1a71a Mon Sep 17 00:00:00 2001
From: Adrian Johnson <adrian.johnson@hashicorp.com>
Date: Thu, 20 Apr 2023 18:14:48 -0500
Subject: [PATCH] allow duplicate tags

---
 internal/service/ec2/vpc_test.go |  9 +++++++--
 internal/tags/key_value_tags.go  | 28 +++++++++++++++++++++++++---
 internal/verify/diff.go          |  4 ----
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/internal/service/ec2/vpc_test.go b/internal/service/ec2/vpc_test.go
index 2a47f5f1d5bc..3e30f5199609 100644
--- a/internal/service/ec2/vpc_test.go
+++ b/internal/service/ec2/vpc_test.go
@@ -403,6 +403,8 @@ func TestAccVPC_DefaultTagsProviderAndResource_overlappingTag(t *testing.T) {
 
 func TestAccVPC_DefaultTagsProviderAndResource_duplicateTag(t *testing.T) {
 	ctx := acctest.Context(t)
+	var vpc ec2.Vpc
+	resourceName := "aws_vpc.test"
 
 	resource.ParallelTest(t, resource.TestCase{
 		PreCheck:                 func() { acctest.PreCheck(ctx, t) },
@@ -415,8 +417,11 @@ func TestAccVPC_DefaultTagsProviderAndResource_duplicateTag(t *testing.T) {
 					acctest.ConfigDefaultTags_Tags1("overlapkey", "overlapvalue"),
 					testAccVPCConfig_tags1("overlapkey", "overlapvalue"),
 				),
-				PlanOnly:    true,
-				ExpectError: regexp.MustCompile(`"tags" are identical to those in the "default_tags" configuration block`),
+				Check: resource.ComposeTestCheckFunc(
+					acctest.CheckVPCExists(ctx, resourceName, &vpc),
+					resource.TestCheckResourceAttr(resourceName, "tags.%", "1"),
+					resource.TestCheckResourceAttr(resourceName, "tags_all.%", "1"),
+				),
 			},
 		},
 	})
diff --git a/internal/tags/key_value_tags.go b/internal/tags/key_value_tags.go
index b39538763163..11a82a0ec881 100644
--- a/internal/tags/key_value_tags.go
+++ b/internal/tags/key_value_tags.go
@@ -754,15 +754,28 @@ func (tags KeyValueTags) RemoveDuplicates(ctx context.Context, defaultConfig *De
 	configTags := make(map[string]string)
 	if config := d.GetRawPlan(); !config.IsNull() && config.IsKnown() {
 		c := config.GetAttr("tags")
-		if !c.IsNull() {
+		if !c.IsNull() && c.IsKnown() {
 			for k, v := range c.AsValueMap() {
 				configTags[k] = v.AsString()
 			}
 		}
 	}
 
+	var configIsNull bool
 	if config := d.GetRawConfig(); !config.IsNull() && config.IsKnown() {
 		c := config.GetAttr("tags")
+		configIsNull = c.IsNull()
+		if !c.IsNull() && c.IsKnown() {
+			for k, v := range c.AsValueMap() {
+				if _, ok := configTags[k]; !ok {
+					configTags[k] = v.AsString()
+				}
+			}
+		}
+	}
+
+	if state := d.GetRawState(); !state.IsNull() && state.IsKnown() {
+		c := state.GetAttr("tags")
 		if !c.IsNull() {
 			for k, v := range c.AsValueMap() {
 				if _, ok := configTags[k]; !ok {
@@ -774,11 +787,20 @@ func (tags KeyValueTags) RemoveDuplicates(ctx context.Context, defaultConfig *De
 
 	for k, v := range configTags {
 		if _, ok := result[k]; !ok {
-			result[k] = v
+			if defaultConfig != nil {
+				if val, ok := defaultConfig.Tags[k]; ok && val.ValueString() == v {
+					result[k] = v
+				}
+			}
 		}
 	}
 
-	return New(ctx, result)
+	out := tags
+	if !configIsNull {
+		out = New(ctx, result)
+	}
+	
+	return out
 }
 
 // ToSnakeCase converts a string to snake case.
diff --git a/internal/verify/diff.go b/internal/verify/diff.go
index 7ea2d7a5f2dd..64f5c80d6fbb 100644
--- a/internal/verify/diff.go
+++ b/internal/verify/diff.go
@@ -26,10 +26,6 @@ func SetTagsDiff(ctx context.Context, diff *schema.ResourceDiff, meta interface{
 
 	resourceTags := tftags.New(ctx, diff.Get("tags").(map[string]interface{}))
 
-	//if defaultTagsConfig.TagsEqual(resourceTags) {
-	//	return fmt.Errorf(`"tags" are identical to those in the "default_tags" configuration block of the provider: please de-duplicate and try again`)
-	//}
-
 	allTags := defaultTagsConfig.MergeTags(resourceTags).IgnoreConfig(ignoreTagsConfig)
 	// To ensure "tags_all" is correctly computed, we explicitly set the attribute diff
 	// when the merger of resource-level tags onto provider-level tags results in n > 0 tags,