Implement short syntax for env variables in compose.yml "environment:"

This commit allows compose file to directly use environment variable
values in "environment:" section when variables were set in `.env` file.
This functionality was missing, as docker-compose supports both: short
and variable interpolation syntax forms:
environment:
	- FOO
and
environment:
	- FOO=${FOO}
Relevant docker-compose documentation:
https://docs.docker.com/compose/how-tos/environment-variables/set-environment-variables/
podman-compose is more compatible with docker-compose after this change.

Signed-off-by: Monika Kairaityte <monika@kibit.lt>

Author: mokibit

newsfragments/fix-short-syntax-env-variables.bugfix

@@ -0,0 +1 @@
+Implemented short syntax for environment variables set in `.env` for compose.yml "environment:" section.

podman_compose.py

@@ -1159,7 +1159,14 @@ async def container_to_args(
             podman_args.extend(["-e", e])
     env = norm_as_list(cnt.get("environment", {}))
     for e in env:
-        podman_args.extend(["-e", e])
+        # new environment variable is set
+        if "=" in e:
+            podman_args.extend(["-e", e])
+        else:
+            # environment variable already exists in environment so pass its value
+            if e in compose.environ.keys():
+                podman_args.extend(["-e", f"{e}={compose.environ[e]}"])
+
     tmpfs_ls = cnt.get("tmpfs", [])
     if isinstance(tmpfs_ls, str):
         tmpfs_ls = [tmpfs_ls]

tests/integration/env_file_tests/project/.env

@@ -1,2 +1,3 @@
 ZZVAR1='This value is loaded but should be overwritten'
 ZZVAR2='This value is loaded from .env in project/ directory'
+ZZVAR3=TEST

tests/integration/env_file_tests/project/container-compose.short_syntax.yaml

@@ -0,0 +1,10 @@
+services:
+  app:
+    image: nopush/podman-compose-test
+    command: ["/bin/busybox", "sh", "-c", "env | grep ZZVAR3"]
+    # 'env_file:' section is not used, so .env file is searched in the same directory as compose.yml
+    # file
+    environment:
+        # this is short syntax: podman-compose takes only this variable value from '.env' file and
+        # sends it to container environment
+        - ZZVAR3

tests/integration/env_file_tests/test_podman_compose_env_file.py

@@ -233,7 +233,7 @@ def test_taking_env_variables_from_env_files_from_different_directories(self) ->
                 [
                     'ZZVAR1=This value is loaded but should be overwritten\r',
                     'ZZVAR2=This value is loaded from .env in project/ directory\r',
-                    'ZZVAR3=\r',
+                    'ZZVAR3=TEST\r',
                     '',
                 ],
             )
@@ -244,3 +244,36 @@ def test_taking_env_variables_from_env_files_from_different_directories(self) ->
                 path_compose_file,
                 "down",
             ])
+
+    def test_env_var_value_accessed_in_compose_file_short_syntax(self) -> None:
+        # Test that compose file can access the environment variable set in .env file using
+        # short syntax, that is: only the name of environment variable is used in "environment:" in
+        # compose.yml file and its value is picked up directly from .env file
+        # long syntax of environment variables interpolation is tested in
+        # tests/integration/interpolation
+
+        base_path = compose_base_path()
+        compose_file_path = os.path.join(base_path, "project/container-compose.short_syntax.yaml")
+        try:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_file_path,
+                "up",
+                "-d",
+            ])
+            output, _ = self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_file_path,
+                "logs",
+            ])
+            # ZZVAR3 was set in .env file
+            self.assertEqual(output, b"ZZVAR3=TEST\n")
+        finally:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_file_path,
+                "down",
+            ])

tests/unit/test_container_to_args.py

@@ -262,6 +262,42 @@ async def test_no_hosts_extension(self) -> None:
             ],
         )
 
+    @parameterized.expand([
+        # short syntax: only take this specific environment variable value from .env file
+        ("use_env_var_from_default_env_file_short_syntax", ["ZZVAR1"], "ZZVAR1=TEST1"),
+        # long syntax: environment variable value from .env file is taken through variable
+        # interpolation
+        # only the value required in 'environment:' compose file is sent to containers
+        # environment
+        ("use_env_var_from_default_env_file_long_syntax", ["ZZVAR1=TEST1"], "ZZVAR1=TEST1"),
+        # "environment:" section in compose file overrides environment variable value from .env file
+        (
+            "use_env_var_from_default_env_file_override_value",
+            ["ZZVAR1=NEW_TEST1"],
+            "ZZVAR1=NEW_TEST1",
+        ),
+    ])
+    async def test_env_file(self, test_name: str, cnt_env: list, expected_var: str) -> None:
+        c = create_compose_mock()
+        # environment variables were set in .env file
+        c.environ = {"ZZVAR1": "TEST1", "ZZVAR2": "TEST2"}
+
+        cnt = get_minimal_container()
+        cnt["environment"] = cnt_env
+
+        args = await container_to_args(c, cnt)
+        self.assertEqual(
+            args,
+            [
+                "--name=project_name_service_name1",
+                "-d",
+                "-e",
+                f"{expected_var}",
+                "--network=bridge:alias=service_name",
+                "busybox",
+            ],
+        )
+
     async def test_env_file_str(self) -> None:
         c = create_compose_mock()