Support variable interpolation in service env_file files

newsfragments/interpolate_service_env_file.feature

@@ -0,0 +1 @@
+Support variable interpolation in service-level env_file files, allowing references to project environment variables using both ``${VAR}`` and ``$VAR`` syntaxes.

podman_compose.py

@@ -16,6 +16,7 @@
 import glob
 import hashlib
 import inspect
+import io
 import json
 import logging
 import os
@@ -1398,7 +1399,11 @@ async def container_to_args(
                 continue
             raise ValueError(f"Env file at {i} does not exist")
         dotenv_dict = {}
-        dotenv_dict = dotenv_to_dict(i)
+        project_environ = getattr(compose, 'environ', None)
+        if isinstance(project_environ, dict):
+            dotenv_dict = dotenv_to_dict(i, project_environ)
+        else:
+            dotenv_dict = dotenv_to_dict(i)
         env = norm_as_list(dotenv_dict)
         for e in env:
             podman_args.extend(["-e", e])
@@ -2343,10 +2348,31 @@ def resolve_extends(
         services[name] = new_service
 
 
-def dotenv_to_dict(dotenv_path: str) -> dict[str, str | None]:
+def _preprocess_env_file(content: str) -> str:
+    """Replace $VAR with ${VAR} so python-dotenv can interpolate both syntaxes."""
+    # Replace $VAR with ${VAR} but leave $$ and ${VAR} unchanged.
+    # Match $ followed by a valid variable name (alphanumeric + underscore),
+    # but not when preceded by another $ or followed by {.
+    return re.sub(r"(?<!\$)\$(?!\$)(?!\{)([A-Za-z_][A-Za-z0-9_]*)", r"${\1}", content)
+
+
+def dotenv_to_dict(
+    dotenv_path: str, environ: dict[str, str | None] | None = None
+) -> dict[str, str | None]:
     if not os.path.isfile(dotenv_path):
         return {}
-    return dotenv_values(dotenv_path)
+    with open(dotenv_path, encoding="utf-8") as fh:
+        content = fh.read()
+    content = _preprocess_env_file(content)
+    if environ:
+        original_environ = dict(os.environ)
+        os.environ.update({k: v for k, v in environ.items() if v is not None})
+        try:
+            return dotenv_values(stream=io.StringIO(content))
+        finally:
+            os.environ.clear()
+            os.environ.update(original_environ)
+    return dotenv_values(stream=io.StringIO(content))
 
 
 COMPOSE_DEFAULT_LS = [

tests/integration/env_file_interpolation/.env

@@ -0,0 +1 @@
+BAR=bar

tests/integration/env_file_interpolation/.env.extra

@@ -0,0 +1 @@
+FOO=${BAR}

tests/integration/env_file_interpolation/docker-compose.yml

@@ -0,0 +1,5 @@
+services:
+  app:
+    image: nopush/podman-compose-test
+    env_file: .env.extra
+    command: ["/bin/sh", "-c", "env | grep '^FOO='"]

tests/integration/env_file_interpolation/test_env_file_interpolation.py

@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import unittest
+
+from tests.integration.test_utils import RunSubprocessMixin
+from tests.integration.test_utils import podman_compose_path
+from tests.integration.test_utils import test_path
+
+
+def compose_base_path() -> str:
+    return os.path.join(test_path(), "env_file_interpolation")
+
+
+class TestEnvFileInterpolation(unittest.TestCase, RunSubprocessMixin):
+    def test_env_file_interpolates_from_project_dotenv(self) -> None:
+        base_path = compose_base_path()
+        path_compose_file = os.path.join(base_path, "docker-compose.yml")
+        try:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                path_compose_file,
+                "up",
+            ])
+            output, _ = self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                path_compose_file,
+                "logs",
+                "--no-log-prefix",
+                "--no-color",
+            ])
+            self.assertEqual(output, b"FOO=bar\n")
+        finally:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                path_compose_file,
+                "down",
+            ])

tests/unit/test_container_to_args.py

@@ -1355,3 +1355,29 @@ async def test_entrypoint_string_is_shlex_split(self) -> None:
                 "busybox",
             ],
         )
+
+    async def test_env_file_interpolates_from_project_dotenv_braces(self) -> None:
+        """Env file values with ${VAR} should interpolate using project .env variables."""
+        c = create_compose_mock()
+        c.environ = {"BAR": "bar"}
+
+        cnt = get_minimal_container()
+        env_file = get_test_file_path('tests/integration/env_file_interpolation/.env.extra')
+        cnt['env_file'] = env_file
+
+        args = await container_to_args(c, cnt)
+        self.assertIn("-e", args)
+        self.assertIn("FOO=bar", args)
+
+    async def test_env_file_interpolates_from_project_dotenv_no_braces(self) -> None:
+        """Env file values with $VAR should interpolate using project .env variables."""
+        c = create_compose_mock()
+        c.environ = {"BAR": "bar"}
+
+        cnt = get_minimal_container()
+        env_file = get_test_file_path('tests/integration/env_file_interpolation/.env.extra')
+        cnt['env_file'] = env_file
+
+        args = await container_to_args(c, cnt)
+        self.assertIn("-e", args)
+        self.assertIn("FOO=bar", args)