feat: Add product version to API response headers (#5366)

Author: emyller

api/app/settings/common.py

@@ -285,6 +285,7 @@
     ],
 }
 MIDDLEWARE = [
+    "common.core.middleware.APIResponseVersionHeaderMiddleware",
     "common.gunicorn.middleware.RouteLoggerMiddleware",
     "django.middleware.security.SecurityMiddleware",
     "whitenoise.middleware.WhiteNoiseMiddleware",

api/conftest.py

@@ -1,7 +1,6 @@
-import importlib
-import inspect
 import logging
 import os
+import site
 import typing
 from unittest.mock import MagicMock
 
@@ -22,7 +21,6 @@
 from moto import mock_dynamodb  # type: ignore[import-untyped]
 from mypy_boto3_dynamodb.service_resource import DynamoDBServiceResource, Table
 from pyfakefs.fake_filesystem import FakeFilesystem
-from pyfakefs.fake_filesystem_unittest import Patcher
 from pytest_django.fixtures import SettingsWrapper
 from pytest_django.plugin import blocking_manager_key
 from pytest_mock import MockerFixture
@@ -138,21 +136,19 @@ def pytest_configure(config: pytest.Config) -> None:
 
 
 @pytest.fixture
-def fs() -> typing.Generator[FakeFilesystem | None, None, None]:
-    app_path = os.path.dirname(os.path.abspath(__file__))
-    real_paths = [app_path]
-
-    for module_name in (
-        "django",
-        "tzdata",
-    ):
-        module_file = inspect.getfile(importlib.import_module(module_name))
-        real_paths.append(os.path.dirname(os.path.abspath(module_file)))
+def fs(fs: FakeFilesystem) -> FakeFilesystem:
+    """
+    Provide a fake filesystem for tests
 
-    with Patcher() as patcher:
-        if fs := patcher.fs:
-            fs.add_real_paths(real_paths)
-        yield fs
+    NOTE: Sometimes pyfakefs patching goes wonky, causing the fake file system
+    to be cached across tests. This can lead tests failing to access real files
+    even if they do not use this fixture. Because we can't fix this issue now,
+    it's safer to allow site-packages [read-only] access from tests.
+    """
+    app_path = os.path.dirname(os.path.abspath(__file__))
+    site_packages = site.getsitepackages()  # Allow files within dependencies
+    fs.add_real_paths([*site_packages, app_path])
+    return fs
 
 
 @pytest.fixture(scope="session")

api/tests/integration/test_integration_api_version_header.py

@@ -0,0 +1,61 @@
+import pytest
+from common.core.utils import get_file_contents, get_versions_from_manifest
+from pyfakefs.fake_filesystem import FakeFilesystem
+from rest_framework import status
+from rest_framework.test import APIClient
+
+
+@pytest.fixture(autouse=True)
+def clear_lru_caches() -> None:
+    get_file_contents.cache_clear()
+    get_versions_from_manifest.cache_clear()
+
+
+@pytest.mark.parametrize(
+    "url",
+    [
+        "/robots.txt",
+        "/api/v1/auth/users/me/",
+    ],
+)
+@pytest.mark.parametrize(
+    "version_file_contents, expected_version",
+    [
+        ('{".": "v1.2.3"}', "v1.2.3"),
+        ('{"foo": "bar"}', "unknown"),
+        ("", "unknown"),
+    ],
+)
+def test_api_version_is_added_to_success_response_headers(
+    admin_client: APIClient,
+    expected_version: str,
+    fs: FakeFilesystem,
+    url: str,
+    version_file_contents: str,
+) -> None:
+    fs.create_file(".versions.json", contents=version_file_contents)
+
+    response = admin_client.get(url)
+    assert response.status_code == status.HTTP_200_OK
+    assert response.headers["Flagsmith-Version"] == expected_version
+
+
+@pytest.mark.parametrize(
+    "version_file_contents, expected_version",
+    [
+        ('{".": "v1.2.3"}', "v1.2.3"),
+        ('{"foo": "bar"}', "unknown"),
+        ("", "unknown"),
+    ],
+)
+def test_api_version_is_added_to_error_response_headers(
+    client: APIClient,
+    expected_version: str,
+    fs: FakeFilesystem,
+    version_file_contents: str,
+) -> None:
+    fs.create_file(".versions.json", contents=version_file_contents)
+
+    response = client.get("/wat")
+    assert response.status_code == status.HTTP_404_NOT_FOUND
+    assert response.headers["Flagsmith-Version"] == expected_version