scripts: runners: add type checking for west_commands

Use mypy to type check the runners package.

The test procedure is now annoying enough to replicate locally that
I'm going to wrap it in a script. Do this for both UNIX and Windows
environments by writing that script in Python.

Keep the GitHub workflow up to date so we now get mypy results in CI.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

.github/workflows/west_cmds.yml

@@ -54,12 +54,13 @@ jobs:
           ${{ runner.os }}-pip-${{ matrix.python-version }}
     - name: install pytest
       run: |
-        pip3 install pytest west pyelftools canopen progress
+        pip3 install wheel
+        pip3 install pytest west pyelftools canopen progress mypy
     - name: run pytest-win
       if: runner.os == 'Windows'
       run: |
-        cmd /C "set PYTHONPATH=.\scripts\west_commands && pytest ./scripts/west_commands/tests/"
+        python ./scripts/west_commands/run_tests.py
     - name: run pytest-mac-linux
       if: runner.os != 'Windows'
       run: |
-        PYTHONPATH=./scripts/west_commands pytest ./scripts/west_commands/tests/
+        ./scripts/west_commands/run_tests.py

scripts/requirements-build-test.txt

@@ -18,6 +18,7 @@ coverage
 
 # used for west-command testing
 pytest
+mypy
 
 # used for mocking functions in pytest
 mock>=4.0.1

scripts/west_commands/README.txt

@@ -1,22 +1,22 @@
 This directory contains implementations for west commands which are
-tightly coupled to the zephyr tree. Currently, those are the build,
-flash, and debug commands.
+tightly coupled to the zephyr tree. This includes the build, flash,
+and debug commands.
 
 Before adding more here, consider whether you might want to put new
 extensions in upstream west. For example, any commands which operate
 on the multi-repo need to be in upstream west, not here. Try to limit
-what goes in here to just those files that change along with Zephyr
-itself.
+what goes in here to Zephyr-specific features.
 
 When extending this code, please keep the unit tests (in tests/) up to
-date. You can run the tests with this command from this directory:
+date. The mypy static type checker is also run on the runners package.
 
-$ PYTHONPATH=$PWD py.test
+To run these tests locally on Windows, run:
 
-Windows users will need to find the path to .west/west/src in their
-Zephyr installation, then run something like this:
+   py -3 run_tests.py
 
-> cmd /C "set PYTHONPATH=path\to\zephyr\scripts\west_commands && py.test"
+On macOS and Linux:
+
+   ./run_tests.py
 
 Note that these tests are run as part of Zephyr's CI when submitting
 an upstream pull request, and pull requests which break the tests

scripts/west_commands/mypy.ini

@@ -0,0 +1,2 @@
+[mypy]
+ignore_missing_imports=True

scripts/west_commands/run_tests.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2020 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# A convenience script provided for running tests on the runners
+# package. Runs mypy and pytest. Any extra arguments in sys.argv are
+# passed along to pytest.
+#
+# Using tox was considered, but rejected as overkill for now.
+#
+# We would have to configure tox to create the test virtualenv with
+# all of zephyr's scripts/requirements.txt, which seems like too much
+# effort for now. We just run in the same Python environment as the
+# user for developer testing and trust CI to set that environment up
+# properly for integration testing.
+#
+# If this file starts to reimplement too many features that are
+# already available in tox, we can revisit this decision.
+
+import os
+import shlex
+import subprocess
+import sys
+
+here = os.path.abspath(os.path.dirname(__file__))
+
+mypy = [sys.executable, '-m', 'mypy', f'--config-file={here}/mypy.ini',
+        '--package', 'runners']
+pytest = [sys.executable, '-m', 'pytest'] + sys.argv[1:]
+
+print(f'Running mypy from {here}:\n\t' +
+      ' '.join(shlex.quote(s) for s in mypy),
+      flush=True)
+subprocess.run(mypy, check=True, cwd=here)
+print(f'Running pytest from {here}:\n\t' +
+      ' '.join(shlex.quote(s) for s in pytest),
+      flush=True)
+subprocess.run(pytest, check=True, cwd=here)