fix: display no outputs if outputs are not defined. (aws#1790)

Why is this change necessary?

* bug from previous PR which always looked for outputs in deployed
templates.

How does it address the issue?

* Explicitly check for outputs, before attempting to display them.
* Added extra tests to verify so that it does not cause regressions in
the future.

What side effects does this change have?

* None.

samcli/lib/deploy/deployer.py

@@ -401,7 +401,8 @@ def wait_for_execute(self, stack_name, changeset_type):
             raise deploy_exceptions.DeployFailedError(stack_name=stack_name, msg=str(ex))
 
         outputs = self.get_stack_outputs(stack_name=stack_name, echo=False)
-        self._stack_outputs(outputs)
+        if outputs:
+            self._display_stack_outputs(outputs)
 
     def create_and_wait_for_changeset(
         self, stack_name, cfn_template, parameter_values, capabilities, role_arn, notification_arns, s3_uploader, tags
@@ -419,7 +420,7 @@ def create_and_wait_for_changeset(
     @pprint_column_names(
         format_string=OUTPUTS_FORMAT_STRING, format_kwargs=OUTPUTS_DEFAULTS_ARGS, table_header=OUTPUTS_TABLE_HEADER_NAME
     )
-    def _stack_outputs(self, stack_outputs, **kwargs):
+    def _display_stack_outputs(self, stack_outputs, **kwargs):
         for counter, output in enumerate(stack_outputs):
             for k, v in [
                 ("Key", output.get("OutputKey")),
@@ -448,7 +449,7 @@ def get_stack_outputs(self, stack_name, echo=True):
                 if echo:
                     sys.stdout.write("\nStack {stack_name} outputs:\n".format(stack_name=stack_name))
                     sys.stdout.flush()
-                    self._stack_outputs(stack_outputs=outputs)
+                    self._display_stack_outputs(stack_outputs=outputs)
                 return outputs
             except KeyError:
                 return None

tests/unit/lib/deploy/test_deployer.py

@@ -598,3 +598,31 @@ def test_get_stack_outputs_exception(self):
 
         with self.assertRaises(DeployStackOutPutFailedError):
             self.deployer.get_stack_outputs(stack_name="test")
+
+    @patch("time.sleep")
+    def test_wait_for_execute_no_outputs(self, patched_time):
+        self.deployer.describe_stack_events = MagicMock()
+        self.deployer._client.get_waiter = MagicMock(return_value=MockCreateUpdateWaiter())
+        self.deployer._display_stack_outputs = MagicMock()
+        self.deployer.get_stack_outputs = MagicMock(return_value=None)
+        self.deployer.wait_for_execute("test", "CREATE")
+        self.assertEqual(self.deployer._display_stack_outputs.call_count, 0)
+
+    @patch("time.sleep")
+    def test_wait_for_execute_with_outputs(self, patched_time):
+        self.deployer.describe_stack_events = MagicMock()
+        outputs = {
+            "Stacks": [
+                {
+                    "Outputs": [
+                        {"OutputKey": "Key1", "OutputValue": "Value1", "Description": "output for s3"},
+                        {"OutputKey": "Key2", "OutputValue": "Value2", "Description": "output for kms"},
+                    ]
+                }
+            ]
+        }
+        self.deployer._client.get_waiter = MagicMock(return_value=MockCreateUpdateWaiter())
+        self.deployer._display_stack_outputs = MagicMock()
+        self.deployer.get_stack_outputs = MagicMock(return_value=outputs["Stacks"][0]["Outputs"])
+        self.deployer.wait_for_execute("test", "CREATE")
+        self.assertEqual(self.deployer._display_stack_outputs.call_count, 1)