docker_swarm_service: Extend env and add env_files support (#51762)

* Extend env and add env_files support

* Python 2.6 compat

* Handle lists passed as string

* Add changelog fragment

* Use correct link formatting

Co-Authored-By: hannseman <hannes@5monkeys.se>

* Fix typo

Co-Authored-By: hannseman <hannes@5monkeys.se>

* Handle empty env and env_files values

test/units/modules/cloud/docker/test_docker_swarm_service.py

@@ -2,7 +2,6 @@ import pytest
 
 
 class APIErrorMock(Exception):
-
     def __init__(self, message, response=None, explanation=None):
         self.message = message
         self.response = response
@@ -26,6 +25,7 @@ def docker_module_mock(mocker):
 @pytest.fixture(autouse=True)
 def docker_swarm_service():
     from ansible.modules.cloud.docker import docker_swarm_service
+
     return docker_swarm_service
 
 
@@ -46,14 +46,55 @@ def test_retry_on_out_of_sequence_error(mocker, docker_swarm_service):
 
 def test_no_retry_on_general_api_error(mocker, docker_swarm_service):
     run_mock = mocker.MagicMock(
-        side_effect=APIErrorMock(
-            message='',
-            response=None,
-            explanation='some error',
-        )
+        side_effect=APIErrorMock(message='', response=None, explanation='some error')
     )
     manager = docker_swarm_service.DockerServiceManager(client=None)
     manager.run = run_mock
     with pytest.raises(APIErrorMock):
         manager.run_safe()
     assert run_mock.call_count == 1
+
+
+def test_get_docker_environment(mocker, docker_swarm_service):
+    env_file_result = {'TEST1': 'A', 'TEST2': 'B', 'TEST3': 'C'}
+    env_dict = {'TEST3': 'CC', 'TEST4': 'D'}
+    env_string = "TEST3=CC,TEST4=D"
+
+    env_list = ['TEST3=CC', 'TEST4=D']
+    expected_result = sorted(['TEST1=A', 'TEST2=B', 'TEST3=CC', 'TEST4=D'])
+    mocker.patch.object(
+        docker_swarm_service, 'parse_env_file', return_value=env_file_result
+    )
+    mocker.patch.object(
+        docker_swarm_service,
+        'format_environment',
+        side_effect=lambda d: ['{0}={1}'.format(key, value) for key, value in d.items()],
+    )
+    # Test with env dict and file
+    result = docker_swarm_service.get_docker_environment(
+        env_dict, env_files=['dummypath']
+    )
+    assert result == expected_result
+    # Test with env list and file
+    result = docker_swarm_service.get_docker_environment(
+        env_list,
+        env_files=['dummypath']
+    )
+    assert result == expected_result
+    # Test with env string and file
+    result = docker_swarm_service.get_docker_environment(
+        env_string, env_files=['dummypath']
+    )
+    assert result == expected_result
+
+    assert result == expected_result
+    # Test with empty env
+    result = docker_swarm_service.get_docker_environment(
+        [], env_files=None
+    )
+    assert result == []
+    # Test with empty env_files
+    result = docker_swarm_service.get_docker_environment(
+        None, env_files=[]
+    )
+    assert result == []