add --skip-env-file option

Fixes #6741
Updates #6511

compose/cli/command.py

@@ -39,8 +39,12 @@
 
 def project_from_options(project_dir, options, additional_options={}):
     override_dir = options.get('--project-directory')
-    environment_file = options.get('--env-file')
-    environment = Environment.from_env_file(override_dir or project_dir, environment_file)
+    skip_environment_file = options.get('--skip-env-file')
+    if skip_environment_file:
+        environment = Environment.from_nothing()
+    else:
+        environment_file = options.get('--env-file')
+        environment = Environment.from_env_file(override_dir or project_dir, environment_file)
     environment.silent = options.get('COMMAND', None) in SILENT_COMMANDS
     set_parallel_limit(environment)
 
@@ -79,8 +83,12 @@ def set_parallel_limit(environment):
 
 def get_config_from_options(base_dir, options, additional_options={}):
     override_dir = options.get('--project-directory')
-    environment_file = options.get('--env-file')
-    environment = Environment.from_env_file(override_dir or base_dir, environment_file)
+    skip_environment_file = options.get('--skip-env-file')
+    if skip_environment_file:
+        environment = Environment.from_nothing()
+    else:
+        environment_file = options.get('--env-file')
+        environment = Environment.from_env_file(override_dir or base_dir, environment_file)
     config_path = get_config_path_from_options(
         base_dir, options, environment
     )

compose/cli/main.py

@@ -209,6 +209,7 @@ class TopLevelCommand(object):
       --compatibility             If set, Compose will attempt to convert keys
                                   in v3 files to their non-Swarm equivalent
       --env-file PATH             Specify an alternate environment file
+      --skip-env-file             Skip loading an environment file
 
     Commands:
       build              Build or rebuild services
@@ -249,8 +250,13 @@ def project_dir(self):
 
     @property
     def toplevel_environment(self):
-        environment_file = self.toplevel_options.get('--env-file')
-        return Environment.from_env_file(self.project_dir, environment_file)
+        skip_environment_file = self.toplevel_options.get('--skip-env-file')
+        if skip_environment_file:
+            environment = Environment.from_nothing()
+        else:
+            environment_file = self.toplevel_options.get('--env-file')
+            environment = Environment.from_env_file(self.project_dir, environment_file)
+        return environment
 
     def build(self, options):
         """

compose/config/environment.py

@@ -58,6 +58,12 @@ def __init__(self, *args, **kwargs):
         self.missing_keys = []
         self.silent = False
 
+    @classmethod
+    def from_nothing(cls):
+        instance = cls()
+        instance.update(os.environ)
+        return instance
+
     @classmethod
     def from_env_file(cls, base_dir, env_file=None):
         def _initialize():

tests/fixtures/env-file-skip/.env

@@ -0,0 +1 @@
+VAR2=VAL2

tests/fixtures/env-file-skip/docker-compose.yml

@@ -0,0 +1,9 @@
+version: '3'
+services:
+  show_env:
+    image: alpine:latest
+    environment:
+      VAR1: VAL1
+      VAR2: $VAR2
+    command:
+      env

tests/integration/environment_test.py

@@ -68,3 +68,16 @@ def test_env_file_override(self):
         assert "WHEREAMI=override" in containers[0].get('Config.Env')
         assert "DEFAULT_CONF_LOADED=true" in containers[0].get('Config.Env')
         dispatch(base_dir, ['--env-file', '.env.override', 'down'], None)
+
+
+class EnvironmentSkipFileTest(DockerClientTestCase):
+    def test_env_file_skip(self):
+        base_dir = 'tests/fixtures/env-file-skip'
+
+        result = dispatch(base_dir, ['up'])
+        assert "VAR1=VAL1" in result.stdout
+        assert "VAR2=VAL2" in result.stdout
+
+        result = dispatch(base_dir, ['--skip-env-file', 'up'])
+        assert "VAR1=VAL1" in result.stdout
+        assert "VAR2=VAL2" not in result.stdout