Make sure run_command properly combines envs (#3104)

Because dictionary's update method updates data in place and does not
return anything back, the run_command method executed baked commands
with env overrides with an empty env. This commit makes sure
environments are properly combined.

.github/workflows/tox.yml

@@ -25,17 +25,17 @@ jobs:
           - tox_env: lint
           - tox_env: docs
           - tox_env: py36
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: py37
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: py38
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: py39
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: py36-devel
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: py39-devel
-            PREFIX: PYTEST_REQPASS=430
+            PREFIX: PYTEST_REQPASS=433
           - tox_env: packaging
           - tox_env: eco
           - tox_env: dockerfile

src/molecule/test/unit/test_util.py

@@ -120,6 +120,39 @@ def test_run_command_with_debug(mocker, patched_print_debug):
     assert x == patched_print_debug.mock_calls
 
 
+def test_run_command_baked_env(mocker):
+    run_mock = mocker.patch.object(util, "run")
+    run_mock.return_value = mocker.Mock(returncode=0)
+    cmd = util.BakedCommand(cmd=["ls"], env=None)
+
+    util.run_command(cmd, env=dict(myvar="myrealvalue"))
+
+    # call_args[1] contains kwargs
+    assert run_mock.call_args[1]["env"] == dict(myvar="myrealvalue")
+
+
+def test_run_command_baked_cmd_env(mocker):
+    run_mock = mocker.patch.object(util, "run")
+    run_mock.return_value = mocker.Mock(returncode=0)
+    cmd = util.BakedCommand(cmd=["ls"], env=dict(myvar="myvalue"))
+
+    util.run_command(cmd)
+
+    # call_args[1] contains kwargs
+    assert run_mock.call_args[1]["env"] == dict(myvar="myvalue")
+
+
+def test_run_command_baked_both_envs(mocker):
+    run_mock = mocker.patch.object(util, "run")
+    run_mock.return_value = mocker.Mock(returncode=0)
+    cmd = util.BakedCommand(cmd=["ls"], env=dict(myvar="myvalue"))
+
+    util.run_command(cmd, env=dict(myvar="myrealvalue"))
+
+    # call_args[1] contains kwargs
+    assert run_mock.call_args[1]["env"] == dict(myvar="myrealvalue")
+
+
 def test_run_command_with_debug_handles_no_env(mocker, patched_print_debug):
     cmd = "ls"
     util.run_command(cmd, debug=True)

src/molecule/util.py

@@ -131,7 +131,10 @@ def run_command(
             "See https://github.com/ansible-community/molecule/issues/2678"
         )
     elif cmd.__class__.__name__ == "BakedCommand":
-        env = cmd.env if not env else cmd.env.copy().update(env)
+        if cmd.env and env:
+            env = dict(cmd.env, **env)
+        else:
+            env = cmd.env or env
         args = cmd.cmd
         stdout = cmd.stdout
         stderr = cmd.stderr