docs: Document static file mount gotcha

README.md

@@ -172,3 +172,11 @@ An APIRouter will be created for each version, with the URL prefix defined by th
   - Pass a `callback` param to `Versionizer` and add your own docs/OpenAPI routes manually for each version
   - If you want a "main" docs page, with all versioned routes included, you can manually add a docs/OpenAPI route to the versioned FastAPI app returned by `Versionizer.versionize()`.
 - See the [Docs Customization](https://github.com/alexschimpf/fastapi-versionizer/tree/main/examples/docs_customization.py) example for more details
+
+## Gotchas
+
+### Static file mounts
+
+If you need to [mount static files](https://fastapi.tiangolo.com/tutorial/static-files/), you'll have to add those to
+your FastAPI app **after** instantiating Versionizer. See the [Static file mount](https://github.com/alexschimpf/fastapi-versionizer/tree/main/examples/with_static_file_mount.py)
+example for more details.

examples/with_static_file_mount.py

@@ -0,0 +1,16 @@
+from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
+
+from fastapi_versionizer import Versionizer
+
+app = FastAPI()
+
+# This will not work!
+app.mount('/examples-not-working', StaticFiles(directory='examples'), name='examples')
+
+versions = Versionizer(
+    app=app,
+).versionize()
+
+# Only static file mounts added *after* instantiating Versionizer will work
+app.mount('/examples', StaticFiles(directory='examples'), name='examples')

tests/test_with_static_file_mount.py

@@ -0,0 +1,21 @@
+from fastapi.testclient import TestClient
+
+from unittest import TestCase
+from examples.with_static_file_mount import app
+
+from pathlib import Path
+
+
+class TestWithStaticFileMount(TestCase):
+    def test_with_static_file_mount_example(self) -> None:
+        test_client = TestClient(app)
+
+        # Read example file from file system
+        expected = Path('examples/with_static_file_mount.py').read_text()
+
+        # Compare local file contents with the same retrieved via the static file mount
+        self.assertEqual(expected, test_client.get('/examples/with_static_file_mount.py').text)
+
+        # Check that a static mount before instantiating Versionizer will not work
+        self.assertEquals('{"detail":"Not Found"}',
+                          test_client.get('/examples-not-working/with_static_file_mount.py').text)