feat: Deliver the deployed API version to an HTTP response header

Author: emyller

src/common/core/middleware.py

@@ -0,0 +1,29 @@
+from typing import Callable
+
+from django.http import HttpRequest, HttpResponse
+
+from common.core.utils import get_versions_from_manifest
+
+
+class APIResponseVersionHeaderMiddleware:
+    """
+    Middleware to add the API version to the response headers
+    """
+
+    def __init__(
+        self,
+        get_response: Callable[[HttpRequest], HttpResponse],
+    ) -> None:
+        self.get_response = get_response
+
+    def __call__(self, request: HttpRequest) -> HttpResponse:
+        response = self.get_response(request)
+        response.headers["X-Flagsmith-Version"] = self.get_version() or "unknown"
+        return response
+    
+    def get_version(self) -> str | None:
+        """Obtains the version number from the manifest file"""
+        manifest_versions = get_versions_from_manifest()
+        if not manifest_versions:
+            return None
+        return manifest_versions.get(".")

src/common/core/utils.py

@@ -55,7 +55,7 @@ def has_email_provider() -> bool:
 
 
 def get_version_info() -> VersionInfo:
-    """Reads the version info baked into src folder of the docker container"""
+    """Returns the version information for the current deployment"""
     _is_saas = is_saas()
     version_json: VersionInfo = {
         "ci_commit_sha": get_file_contents("./CI_COMMIT_SHA") or UNKNOWN,
@@ -66,10 +66,8 @@ def get_version_info() -> VersionInfo:
         "self_hosted_data": None,
     }
 
-    manifest_versions_content = get_file_contents(VERSIONS_INFO_FILE_LOCATION)
-
-    if manifest_versions_content:
-        manifest_versions = json.loads(manifest_versions_content)
+    manifest_versions = get_versions_from_manifest()
+    if manifest_versions:
         version_json["package_versions"] = manifest_versions
         version_json["image_tag"] = manifest_versions["."]
 
@@ -84,6 +82,17 @@ def get_version_info() -> VersionInfo:
     return version_json
 
 
+@lru_cache()
+def get_versions_from_manifest() -> str | None:
+    """Reads the version info baked into the Docker container"""
+    raw_content = get_file_contents(VERSIONS_INFO_FILE_LOCATION)
+    if not raw_content:
+        return None
+    
+    manifest = json.loads(raw_content)
+    return manifest
+
+
 @lru_cache()
 def get_file_contents(file_path: str) -> str | None:
     """Attempts to read a file from the filesystem and return the contents"""

tests/unit/common/core/test_middleware.py

@@ -0,0 +1,53 @@
+import pytest
+from pytest_mock import MockerFixture
+
+from common.core import middleware as middleware_module
+
+
+def test_APIResponseVersionHeaderMiddleware__valid_version_info___adds_version_header(
+    mocker: MockerFixture,
+) -> None:
+    # Given
+    request = mocker.Mock()
+    response = mocker.Mock(headers={})
+    get_response = lambda r: response
+    middleware = middleware_module.APIResponseVersionHeaderMiddleware(get_response)
+    get_versions_from_manifest = mocker.patch.object(
+        middleware_module, "get_versions_from_manifest",
+        return_value={".": "v1.2.3"},
+    )
+
+    # When
+    result = middleware(request)
+
+    # Then
+    assert result == response
+    assert response.headers["X-Flagsmith-Version"] == "v1.2.3"
+    assert get_versions_from_manifest.call_args_list == [mocker.call()]
+
+
+@pytest.mark.parametrize("version_info", [
+    {},
+    None,
+])
+def test_APIResponseVersionHeaderMiddleware__invalid_version_info___adds_unknown_header(
+    mocker: MockerFixture,
+    version_info: dict[str, str] | None,
+) -> None:
+    # Given
+    request = mocker.Mock()
+    response = mocker.Mock(headers={})
+    get_response = lambda r: response
+    middleware = middleware_module.APIResponseVersionHeaderMiddleware(get_response)
+    get_versions_from_manifest = mocker.patch.object(
+        middleware_module, "get_versions_from_manifest",
+        return_value=version_info,
+    )
+
+    # When
+    result = middleware(request)
+
+    # Then
+    assert result == response
+    assert response.headers["X-Flagsmith-Version"] == "unknown"
+    assert get_versions_from_manifest.call_args_list == [mocker.call()]