Support environment files and comments in setenv (#1668)

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

4 files changed, 66 insertions, 5 deletions

diff --git a/docs/changelog/1667.feature.rst b/docs/changelog/1667.feature.rst
new file mode 100644
index 00000000..1a315050
--- /dev/null
+++ b/docs/changelog/1667.feature.rst
@@ -0,0 +1 @@
+Support for comments within ``setenv`` and environment files via the ``files|`` prefix. - by :user:`gaborbernat`
diff --git a/docs/config.rst b/docs/config.rst
index d5fdc2b0..d2d89b71 100644
--- a/docs/config.rst
+++ b/docs/config.rst
@@ -404,6 +404,14 @@ Complete list of settings that you can put into ``testenv*`` sections:
         setenv   =
             PYTHONPATH = {env:PYTHONPATH}{:}{toxinidir}
 
+    .. versionadded:: 3.20
+
+    Support for comments. Lines starting with ``#`` are ignored.
+
+    Support for environment files. Lines starting with the ``file|`` contain path to a environment
+    file to load. Rules within the environment file are the same as within the ``setenv``
+    (same replacement and comment support).
+
 .. conf:: passenv ^ SPACE-SEPARATED-GLOBNAMES
 
     .. versionadded:: 2.0
diff --git a/src/tox/config/__init__.py b/src/tox/config/__init__.py
index b1032f8b..197d14c3 100644
--- a/src/tox/config/__init__.py
+++ b/src/tox/config/__init__.py
@@ -1606,13 +1606,21 @@ class SectionReader:
         if value is None or not replace:
             return default or {}
 
-        d = {}
+        env_values = {}
         for line in value.split(sep):
             if line.strip():
-                name, rest = line.split("=", 1)
-                d[name.strip()] = rest.strip()
-
-        return d
+                if line.startswith("#"):  # comment lines are ignored
+                    pass
+                elif line.startswith("file|"):  # file markers contain paths to env files
+                    file_path = line[5:].strip()
+                    if os.path.exists(file_path):
+                        with open(file_path, "rt") as file_handler:
+                            content = file_handler.read()
+                        env_values.update(self._getdict(content, "", sep, replace))
+                else:
+                    name, value = line.split("=", 1)
+                    env_values[name.strip()] = value.strip()
+        return env_values
 
     def getfloat(self, name, default=None, replace=True):
         s = self.getstring(name, default, replace=replace)
diff --git a/tests/unit/config/test_config.py b/tests/unit/config/test_config.py
index e89c27a4..7eb2ffbc 100644
--- a/tests/unit/config/test_config.py
+++ b/tests/unit/config/test_config.py
@@ -6,6 +6,7 @@ from textwrap import dedent
 import py
 import pytest
 from pluggy import PluginManager
+from six import PY2
 
 import tox
 from tox.config import (
@@ -2668,6 +2669,49 @@ class TestSetenv:
         assert envconfig.setenv["NOT_TEST"] == "defaultvalue"
         assert envconfig.setenv["y"] == "7"
 
+    def test_setenv_comment(self, newconfig):
+        """Check that setenv ignores comments."""
+        envconfig = newconfig(
+            """
+            [testenv]
+            setenv =
+                # MAGIC = yes
+        """,
+        ).envconfigs["python"]
+        assert "MAGIC" not in envconfig.setenv
+
+    @pytest.mark.parametrize(
+        "content, has_magic",
+        [
+            (None, False),
+            ("\n", False),
+            ("#MAGIC = yes", False),
+            ("MAGIC=yes", True),
+            ("\nMAGIC = yes", True),
+        ],
+    )
+    def test_setenv_env_file(self, newconfig, content, has_magic, tmp_path):
+        """Check that setenv handles env files."""
+        env_path = tmp_path / ".env" if content else None
+        if content:
+            env_path.write_text(content.decode() if PY2 else content)
+        env_config = newconfig(
+            """
+            [testenv]
+            setenv =
+                ALPHA = 1
+                file| {}
+        """.format(
+                env_path,
+            ),
+        ).envconfigs["python"]
+        envs = env_config.setenv.definitions
+        assert envs["ALPHA"] == "1"
+        if has_magic:
+            assert envs["MAGIC"] == "yes"
+        else:
+            assert "MAGIC" not in envs
+
 
 class TestIndexServer:
     def test_indexserver(self, newconfig):