feat: Add flag for import existing resources

Pass through option for importing existing resources which allows using
Retain for DeletionPolicy on resources to avoid removal on data
resources if stack needs to be deleted and recreated.

Fixes: #1699

Author: electrofelix

samcli/commands/deploy/command.py

@@ -108,6 +108,13 @@
     is_flag=True,
     help="Prompt to confirm if the computed changeset is to be deployed by SAM CLI.",
 )
+@click.option(
+    "--import-existing-resources/--no-import-existing-resources",
+    default=False,
+    required=False,
+    is_flag=True,
+    help="Requests CloudFormation to import any existing referenced by the template when creating the changeset.",
+)
 @click.option(
     "--disable-rollback/--no-disable-rollback",
     default=False,
@@ -198,6 +205,7 @@ def cli(
     config_file,
     config_env,
     disable_rollback,
+    import_existing_resources,
     on_failure,
     max_wait_duration,
 ):
@@ -234,6 +242,7 @@ def cli(
         config_env,
         resolve_image_repos,
         disable_rollback,
+        import_existing_resources,
         on_failure,
         max_wait_duration,
     )  # pragma: no cover
@@ -268,6 +277,7 @@ def do_cli(
     config_env,
     resolve_image_repos,
     disable_rollback,
+    import_existing_resources,
     on_failure,
     max_wait_duration,
 ):
@@ -373,6 +383,7 @@ def do_cli(
             signing_profiles=guided_context.signing_profiles if guided else signing_profiles,
             use_changeset=True,
             disable_rollback=guided_context.disable_rollback if guided else disable_rollback,
+            import_existing_resources=import_existing_resources,
             poll_delay=poll_delay,
             on_failure=on_failure,
             max_wait_duration=max_wait_duration,

samcli/commands/deploy/core/options.py

@@ -35,6 +35,7 @@
     "fail_on_empty_changeset",
     "confirm_changeset",
     "disable_rollback",
+    "import_existing_resources",
     "on_failure",
     "force_upload",
     "max_wait_duration",

samcli/commands/deploy/deploy_context.py

@@ -72,6 +72,7 @@ def __init__(
         signing_profiles,
         use_changeset,
         disable_rollback,
+        import_existing_resources,
         poll_delay,
         on_failure,
         max_wait_duration,
@@ -104,6 +105,7 @@ def __init__(
         self.signing_profiles = signing_profiles
         self.use_changeset = use_changeset
         self.disable_rollback = disable_rollback
+        self.import_existing_resources = import_existing_resources
         self.poll_delay = poll_delay
         self.on_failure = FailureMode(on_failure) if on_failure else FailureMode.ROLLBACK
         self._max_template_size = 51200
@@ -164,6 +166,7 @@ def run(self):
             self.signing_profiles,
             self.use_changeset,
             self.disable_rollback,
+            self.import_existing_resources,
         )
         return self.deploy(
             self.stack_name,
@@ -180,6 +183,7 @@ def run(self):
             self.confirm_changeset,
             self.use_changeset,
             self.disable_rollback,
+            self.import_existing_resources,
         )
 
     def deploy(
@@ -198,6 +202,7 @@ def deploy(
         confirm_changeset: bool = False,
         use_changeset: bool = True,
         disable_rollback: bool = False,
+        import_existing_resources: bool = False,
     ):
         """
         Deploy the stack to cloudformation.
@@ -234,6 +239,8 @@ def deploy(
             Involve creation of changesets, false when using sam sync
         disable_rollback : bool
             Preserves the state of previously provisioned resources when an operation fails
+        import_existing_resources : bool
+            Changeset should attempt to import existing resources as supported by cloudformation
         """
         stacks, _ = SamLocalStackProvider.get_stacks(
             self.template_file,
@@ -257,6 +264,7 @@ def deploy(
                     notification_arns=notification_arns,
                     s3_uploader=s3_uploader,
                     tags=tags,
+                    import_existing_resources=import_existing_resources,
                 )
                 click.echo(self.MSG_SHOWCASE_CHANGESET.format(changeset_id=result["Id"]))
 

samcli/commands/deploy/utils.py

@@ -20,6 +20,7 @@ def print_deploy_args(
     signing_profiles,
     use_changeset,
     disable_rollback,
+    import_existing_resources,
 ):
     """
     Print a table of the values that are used during a sam deploy.
@@ -33,6 +34,7 @@ def print_deploy_args(
         Region                     : us-east-1
         Confirm changeset          : False
         Disable rollback           : False
+        Import Existing Resources  : False
         Deployment s3 bucket       : aws-sam-cli-managed-default-samclisourcebucket-abcdef
         Capabilities               : ["CAPABILITY_IAM"]
         Parameter overrides        : {'MyParamater': '***', 'Parameter2': 'dd'}
@@ -70,6 +72,7 @@ def print_deploy_args(
     if use_changeset:
         click.echo(f"\tConfirm changeset            : {confirm_changeset}")
     click.echo(f"\tDisable rollback             : {disable_rollback}")
+    click.echo(f"\tImport Existing Resources    : {import_existing_resources}")
     if image_repository:
         msg = "Deployment image repository  : "
         # NOTE(sriram-mv): tab length is 8 spaces.

samcli/commands/sync/command.py

@@ -398,6 +398,7 @@ def do_cli(
                     force_upload=True,
                     signing_profiles=None,
                     disable_rollback=False,
+                    import_existing_resources=False,
                     poll_delay=poll_delay,
                     on_failure=None,
                     max_wait_duration=60,

samcli/lib/deploy/deployer.py

@@ -141,7 +141,16 @@ def has_stack(self, stack_name):
             raise e
 
     def create_changeset(
-        self, stack_name, cfn_template, parameter_values, capabilities, role_arn, notification_arns, s3_uploader, tags
+        self,
+        stack_name,
+        cfn_template,
+        parameter_values,
+        capabilities,
+        role_arn,
+        notification_arns,
+        s3_uploader,
+        tags,
+        import_existing_resources,
     ):
         """
         Call Cloudformation to create a changeset and wait for it to complete
@@ -154,6 +163,7 @@ def create_changeset(
         :param notification_arns: Arns for sending notifications
         :param s3_uploader: S3Uploader object to upload files to S3 buckets
         :param tags: Array of tags passed to CloudFormation
+        :param import_existing_resources: Argument passed to CloudFormation
         :return:
         """
         if not self.has_stack(stack_name):
@@ -183,6 +193,7 @@ def create_changeset(
             "Parameters": parameter_values,
             "Description": "Created by SAM CLI at {0} UTC".format(datetime.utcnow().isoformat()),
             "Tags": tags,
+            "ImportExistingResources": import_existing_resources,
         }
 
         kwargs = self._process_kwargs(kwargs, s3_uploader, capabilities, role_arn, notification_arns)
@@ -245,8 +256,8 @@ def describe_changeset(self, change_set_id, stack_name, **kwargs):
         """
         paginator = self._client.get_paginator("describe_change_set")
         response_iterator = paginator.paginate(ChangeSetName=change_set_id, StackName=stack_name)
-        changes = {"Add": [], "Modify": [], "Remove": []}
-        changes_showcase = {"Add": "+ Add", "Modify": "* Modify", "Remove": "- Delete"}
+        changes = {"Add": [], "Modify": [], "Remove": [], "Import": []}
+        changes_showcase = {"Add": "+ Add", "Modify": "* Modify", "Remove": "- Delete", "Import": "~ Import"}
         changeset = False
         for item in response_iterator:
             cf_changes = item.get("Changes")
@@ -556,11 +567,28 @@ def wait_for_execute(
                 raise ex
 
     def create_and_wait_for_changeset(
-        self, stack_name, cfn_template, parameter_values, capabilities, role_arn, notification_arns, s3_uploader, tags
+        self,
+        stack_name,
+        cfn_template,
+        parameter_values,
+        capabilities,
+        role_arn,
+        notification_arns,
+        s3_uploader,
+        tags,
+        import_existing_resources,
     ):
         try:
             result, changeset_type = self.create_changeset(
-                stack_name, cfn_template, parameter_values, capabilities, role_arn, notification_arns, s3_uploader, tags
+                stack_name,
+                cfn_template,
+                parameter_values,
+                capabilities,
+                role_arn,
+                notification_arns,
+                s3_uploader,
+                tags,
+                import_existing_resources,
             )
             self.wait_for_changeset(result["Id"], stack_name)
             self.describe_changeset(result["Id"], stack_name)

tests/unit/commands/deploy/test_command.py

@@ -50,6 +50,7 @@ def setUp(self):
         self.use_changeset = True
         self.resolve_image_repos = False
         self.disable_rollback = False
+        self.import_existing_resources = False
         self.on_failure = None
         self.max_wait_duration = 480
         MOCK_SAM_CONFIG.reset_mock()
@@ -103,6 +104,7 @@ def test_all_args(self, mock_deploy_context, mock_deploy_click, mock_package_con
             config_file=self.config_file,
             resolve_image_repos=self.resolve_image_repos,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -130,6 +132,7 @@ def test_all_args(self, mock_deploy_context, mock_deploy_click, mock_package_con
             signing_profiles=self.signing_profiles,
             use_changeset=self.use_changeset,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             poll_delay=os.getenv("SAM_CLI_POLL_DELAY"),
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
@@ -221,6 +224,7 @@ def test_all_args_guided_no_to_authorization_confirmation_prompt(
                     config_file=self.config_file,
                     resolve_image_repos=self.resolve_image_repos,
                     disable_rollback=self.disable_rollback,
+                    import_existing_resources=self.import_existing_resources,
                     on_failure=self.on_failure,
                     max_wait_duration=self.max_wait_duration,
                 )
@@ -323,6 +327,7 @@ def test_all_args_guided_use_defaults(
                 config_file=self.config_file,
                 resolve_image_repos=self.resolve_image_repos,
                 disable_rollback=self.disable_rollback,
+                import_existing_resources=self.import_existing_resources,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
             )
@@ -350,6 +355,7 @@ def test_all_args_guided_use_defaults(
                 signing_profiles=self.signing_profiles,
                 use_changeset=self.use_changeset,
                 disable_rollback=True,
+                import_existing_resources=False,
                 poll_delay=5,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
@@ -469,6 +475,7 @@ def test_all_args_guided(
                 config_file=self.config_file,
                 resolve_image_repos=self.resolve_image_repos,
                 disable_rollback=self.disable_rollback,
+                import_existing_resources=self.import_existing_resources,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
             )
@@ -496,6 +503,7 @@ def test_all_args_guided(
                 signing_profiles=self.signing_profiles,
                 use_changeset=self.use_changeset,
                 disable_rollback=True,
+                import_existing_resources=False,
                 poll_delay=5,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
@@ -618,6 +626,7 @@ def test_all_args_guided_no_save_echo_param_to_config(
             config_file=self.config_file,
             resolve_image_repos=self.resolve_image_repos,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -649,6 +658,7 @@ def test_all_args_guided_no_save_echo_param_to_config(
             signing_profiles=self.signing_profiles,
             use_changeset=self.use_changeset,
             disable_rollback=True,
+            import_existing_resources=False,
             poll_delay=5,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
@@ -778,6 +788,7 @@ def test_all_args_guided_no_params_save_config(
             signing_profiles=self.signing_profiles,
             resolve_image_repos=self.resolve_image_repos,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -805,6 +816,7 @@ def test_all_args_guided_no_params_save_config(
             signing_profiles=self.signing_profiles,
             use_changeset=self.use_changeset,
             disable_rollback=True,
+            import_existing_resources=False,
             poll_delay=5,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
@@ -918,6 +930,7 @@ def test_all_args_guided_no_params_no_save_config(
                 signing_profiles=self.signing_profiles,
                 resolve_image_repos=self.resolve_image_repos,
                 disable_rollback=self.disable_rollback,
+                import_existing_resources=self.import_existing_resources,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
             )
@@ -945,6 +958,7 @@ def test_all_args_guided_no_params_no_save_config(
                 signing_profiles=self.signing_profiles,
                 use_changeset=self.use_changeset,
                 disable_rollback=self.disable_rollback,
+                import_existing_resources=self.import_existing_resources,
                 poll_delay=5,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
@@ -996,6 +1010,7 @@ def test_all_args_resolve_s3(
             signing_profiles=self.signing_profiles,
             resolve_image_repos=self.resolve_image_repos,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -1023,6 +1038,7 @@ def test_all_args_resolve_s3(
             signing_profiles=self.signing_profiles,
             use_changeset=self.use_changeset,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             poll_delay=5,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
@@ -1062,6 +1078,7 @@ def test_resolve_s3_and_s3_bucket_both_set(self):
                 signing_profiles=self.signing_profiles,
                 resolve_image_repos=self.resolve_image_repos,
                 disable_rollback=self.disable_rollback,
+                import_existing_resources=self.import_existing_resources,
                 on_failure=self.on_failure,
                 max_wait_duration=self.max_wait_duration,
             )
@@ -1114,6 +1131,7 @@ def test_all_args_resolve_image_repos(
             signing_profiles=self.signing_profiles,
             resolve_image_repos=True,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -1141,6 +1159,7 @@ def test_all_args_resolve_image_repos(
             signing_profiles=self.signing_profiles,
             use_changeset=True,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             poll_delay=5,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
@@ -1189,6 +1208,7 @@ def test_passing_parameter_overrides_to_context(
             config_file=self.config_file,
             resolve_image_repos=self.resolve_image_repos,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,
         )
@@ -1216,6 +1236,7 @@ def test_passing_parameter_overrides_to_context(
             signing_profiles=self.signing_profiles,
             use_changeset=self.use_changeset,
             disable_rollback=self.disable_rollback,
+            import_existing_resources=self.import_existing_resources,
             poll_delay=os.getenv("SAM_CLI_POLL_DELAY"),
             on_failure=self.on_failure,
             max_wait_duration=self.max_wait_duration,