Add missing Fn::GetAtt attributes to S3 bucket mock (#3396)

* Add missing `Fn::GetAtt` attributes to S3 bucket mock

Addresses an issue reported here https://github.com/localstack/aws-cdk-local/issues/1

* Reformat touched files with `black`

* Reformat touched files with `black` on Python 3.7

moto/s3/models.py

@@ -1061,12 +1061,16 @@ class FakeBucket(CloudFormationModel):
     def get_cfn_attribute(self, attribute_name):
         from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
 
-        if attribute_name == "DomainName":
-            raise NotImplementedError('"Fn::GetAtt" : [ "{0}" , "DomainName" ]"')
-        elif attribute_name == "WebsiteURL":
-            raise NotImplementedError('"Fn::GetAtt" : [ "{0}" , "WebsiteURL" ]"')
-        elif attribute_name == "Arn":
+        if attribute_name == "Arn":
             return self.arn
+        elif attribute_name == "DomainName":
+            return self.domain_name
+        elif attribute_name == "DualStackDomainName":
+            return self.dual_stack_domain_name
+        elif attribute_name == "RegionalDomainName":
+            return self.regional_domain_name
+        elif attribute_name == "WebsiteURL":
+            return self.website_url
         raise UnformattedGetAttTemplateException()
 
     def set_acl(self, acl):
@@ -1076,6 +1080,24 @@ class FakeBucket(CloudFormationModel):
     def arn(self):
         return "arn:aws:s3:::{}".format(self.name)
 
+    @property
+    def domain_name(self):
+        return "{}.s3.amazonaws.com".format(self.name)
+
+    @property
+    def dual_stack_domain_name(self):
+        return "{}.s3.dualstack.{}.amazonaws.com".format(self.name, self.region_name)
+
+    @property
+    def regional_domain_name(self):
+        return "{}.s3.{}.amazonaws.com".format(self.name, self.region_name)
+
+    @property
+    def website_url(self):
+        return "http://{}.s3-website.{}.amazonaws.com".format(
+            self.name, self.region_name
+        )
+
     @property
     def physical_resource_id(self):
         return self.name

tests/test_s3/test_s3_cloudformation.py

@@ -148,8 +148,9 @@ def test_s3_bucket_cloudformation_update_replacement():
 @mock_s3
 @mock_cloudformation
 def test_s3_bucket_cloudformation_outputs():
-    s3 = boto3.client("s3", region_name="us-east-1")
-    cf = boto3.resource("cloudformation", region_name="us-east-1")
+    region_name = "us-east-1"
+    s3 = boto3.client("s3", region_name=region_name)
+    cf = boto3.resource("cloudformation", region_name=region_name)
     stack_name = "test-stack"
     bucket_name = "test-bucket"
     template = {
@@ -165,6 +166,26 @@ def test_s3_bucket_cloudformation_outputs():
                 "Value": {"Fn::GetAtt": ["TestBucket", "Arn"]},
                 "Export": {"Name": {"Fn::Sub": "${AWS::StackName}:BucketARN"}},
             },
+            "BucketDomainName": {
+                "Value": {"Fn::GetAtt": ["TestBucket", "DomainName"]},
+                "Export": {"Name": {"Fn::Sub": "${AWS::StackName}:BucketDomainName"}},
+            },
+            "BucketDualStackDomainName": {
+                "Value": {"Fn::GetAtt": ["TestBucket", "DualStackDomainName"]},
+                "Export": {
+                    "Name": {"Fn::Sub": "${AWS::StackName}:BucketDualStackDomainName"}
+                },
+            },
+            "BucketRegionalDomainName": {
+                "Value": {"Fn::GetAtt": ["TestBucket", "RegionalDomainName"]},
+                "Export": {
+                    "Name": {"Fn::Sub": "${AWS::StackName}:BucketRegionalDomainName"}
+                },
+            },
+            "BucketWebsiteURL": {
+                "Value": {"Fn::GetAtt": ["TestBucket", "WebsiteURL"]},
+                "Export": {"Name": {"Fn::Sub": "${AWS::StackName}:BucketWebsiteURL"}},
+            },
             "BucketName": {
                 "Value": {"Ref": "TestBucket"},
                 "Export": {"Name": {"Fn::Sub": "${AWS::StackName}:BucketName"}},
@@ -176,4 +197,22 @@ def test_s3_bucket_cloudformation_outputs():
     output = {item["OutputKey"]: item["OutputValue"] for item in outputs_list}
     s3.head_bucket(Bucket=output["BucketName"])
     output["BucketARN"].should.match("arn:aws:s3.+{bucket}".format(bucket=bucket_name))
+    output["BucketDomainName"].should.equal(
+        "{bucket}.s3.amazonaws.com".format(bucket=bucket_name)
+    )
+    output["BucketDualStackDomainName"].should.equal(
+        "{bucket}.s3.dualstack.{region}.amazonaws.com".format(
+            bucket=bucket_name, region=region_name
+        )
+    )
+    output["BucketRegionalDomainName"].should.equal(
+        "{bucket}.s3.{region}.amazonaws.com".format(
+            bucket=bucket_name, region=region_name
+        )
+    )
+    output["BucketWebsiteURL"].should.equal(
+        "http://{bucket}.s3-website.{region}.amazonaws.com".format(
+            bucket=bucket_name, region=region_name
+        )
+    )
     output["BucketName"].should.equal(bucket_name)