[confcom] Run testing against built extension (#9429)

* [confcom] Run testing against built extension

* Fix style

* Remove flag only supported on later python versions

* .

* Work around azdev test not respecting the session scope

* Add robust session scope mechanism for azdev test

Author: DomAyre

src/confcom/azext_confcom/tests/conftest.py

@@ -0,0 +1,77 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+
+import fcntl
+import importlib
+import os
+import subprocess
+import tempfile
+import psutil
+import pytest
+import sys
+import shutil
+
+from pathlib import Path
+
+
+# This fixture ensures tests are run against final built wheels of the extension
+# instead of the unbuilt local code, which may have breaking differences with
+# the thing we actually ship to users. All but the test modules themselves are
+# replaced with the wheel in case the tests themselves rely on unshipped code.
+@pytest.fixture(autouse=True, scope="session")
+def run_on_wheel(request):
+
+    modules_to_test = {i.module for i in request.session.items}
+    extensions_to_build = {module.__name__.split(".")[0] for module in modules_to_test}
+    extension_dirs = {Path(a.split("/azext_")[0]) for a in request.config.args}
+
+    # Azdev doesn't respect the session scope of the fixture, therefore we need
+    # to implement equivalent behaviour by getting a unique ID for the current
+    # run and using that to determine if wheels have already been built. Search
+    # process parentage until we find the first shell process and use it's
+    # child's PID as the run ID.
+    parent = psutil.Process(os.getpid())
+    while not any(parent.cmdline()[0].endswith(i) for i in ["bash", "sh"]):
+        parent = parent.parent()
+    RUN_ID = parent.children()[0].pid
+
+    build_dir = Path(tempfile.gettempdir()) / f"wheels_{RUN_ID}"
+    build_dir.mkdir(exist_ok=True)
+
+    # Build all extensions being tested into wheels
+    for extension in extensions_to_build:
+
+        extension_name = extension.replace("azext_", "")
+
+        # Ensure we acquire a lock while operating on the build dir to avoid races
+        lock_file = build_dir / ".dir.lock"
+        with lock_file.open("w") as f:
+            fcntl.flock(f, fcntl.LOCK_EX)
+            try:
+
+                # Delete the extensions build dir, as azdev extension build doesn't
+                # reliably handle changes
+                for extension_dir in extension_dirs:
+                    if (extension_dir / "build").exists():
+                        shutil.rmtree((extension_dir / "build").as_posix(), ignore_errors=True)
+
+                if not any(build_dir.glob(f"{extension_name}*.whl")):
+                    subprocess.run(
+                        ["azdev", "extension", "build", extension.replace("azext_", ""), "--dist-dir", build_dir.as_posix()],
+                        check=True,
+                    )
+
+            finally:
+                fcntl.flock(f, fcntl.LOCK_UN)
+
+    # Add the wheel to the path and reload extension modules so the
+    # tests pick up the wheel code over the unbuilt code
+    sys.path.insert(0, build_dir.glob("*.whl").__next__().as_posix())
+    for module in list(sys.modules.values()):
+        if extension in module.__name__ and module not in modules_to_test:
+            del sys.modules[module.__name__]
+            importlib.import_module(module.__name__)
+
+    yield