zephyr: zmake: add re-exec logic

Add some logic to re-exec zmake when running inside of a chroot and we
find the source code available (to reduce the number of times we have
to update the chroot).

Note: we also discussed adding a chroot-upgrade-required warning
logic.  This is actually a separate idea so will be handled in a
separate CL.

BUG=b:197636145
BRANCH=none
TEST=unit tests

Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Change-Id: I26ecbb9a575f22c8667a1928e4bd5836f6fd4fe1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3114503
Reviewed-by: Yuval Peress <peress@chromium.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/zephyr/zmake/tests/test_reexec.py b/zephyr/zmake/tests/test_reexec.py
new file mode 100644
index 0000000000..9f25b5a834
--- /dev/null
+++ b/zephyr/zmake/tests/test_reexec.py
@@ -0,0 +1,59 @@
+# Copyright 2021 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Test the zmake re-exec functionality."""
+
+import os
+import sys
+import unittest.mock as mock
+
+import pytest
+
+import zmake.__main__ as main
+
+
+@pytest.fixture
+def fake_env(monkeypatch):
+    environ = {}
+    monkeypatch.setattr(os, "environ", environ)
+    return environ
+
+
+@pytest.fixture
+def mock_execve():
+    with mock.patch("os.execve", autospec=True) as mocked_function:
+        yield mocked_function
+
+
+def test_out_of_chroot(fake_env, mock_execve):
+    # When CROS_WORKON_SRCROOT is not set, we should not re-exec.
+    main.maybe_reexec(["--help"])
+    mock_execve.assert_not_called()
+
+
+def test_pythonpath_set(fake_env, mock_execve):
+    # With PYTHONPATH set, we should not re-exec.
+    fake_env["CROS_WORKON_SRCROOT"] = "/mnt/host/source"
+    fake_env["PYTHONPATH"] = "/foo/bar/baz"
+    main.maybe_reexec(["--help"])
+    mock_execve.assert_not_called()
+
+
+def test_zmake_does_not_exist(fake_env, mock_execve):
+    # When zmake is not at src/platform/ec/zephyr/zmake, don't re-exec.
+    fake_env["CROS_WORKON_SRCROOT"] = "/this/does/not/exist"
+    main.maybe_reexec(["--help"])
+    mock_execve.assert_not_called()
+
+
+def test_zmake_reexec(fake_env, mock_execve):
+    # Nothing else applies?  The re-exec should happen.
+    fake_env["CROS_WORKON_SRCROOT"] = "/mnt/host/source"
+    main.maybe_reexec(["--help"])
+    new_env = dict(fake_env)
+    new_env["PYTHONPATH"] = "/mnt/host/source/src/platform/ec/zephyr/zmake"
+    mock_execve.assert_called_once_with(
+        sys.executable,
+        [sys.executable, "-m", "zmake", "--help"],
+        new_env,
+    )