chore: import upstream snapshot with attribution

invokeai/app/api/no_cache_staticfiles.py

@@ -0,0 +1,50 @@
+from typing import Any
+
+from starlette.exceptions import HTTPException
+from starlette.responses import Response
+from starlette.staticfiles import StaticFiles
+from starlette.types import Scope
+
+
+class NoCacheStaticFiles(StaticFiles):
+    """
+    This class is used to override the default caching behavior of starlette for static files,
+    ensuring we *never* cache static files. It modifies the file response headers to strictly
+    never cache the files.
+
+    Static files include the javascript bundles, fonts, locales, and some images. Generated
+    images are not included, as they are served by a router.
+
+    This class also implements proper SPA (Single Page Application) routing by serving index.html
+    for any routes that don't match static files, enabling client-side routing to work correctly
+    in production builds.
+    """
+
+    def __init__(self, *args: Any, **kwargs: Any):
+        self.cachecontrol = "max-age=0, no-cache, no-store, , must-revalidate"
+        self.pragma = "no-cache"
+        self.expires = "0"
+        super().__init__(*args, **kwargs)
+
+    def file_response(self, *args: Any, **kwargs: Any) -> Response:
+        resp = super().file_response(*args, **kwargs)
+        resp.headers.setdefault("Cache-Control", self.cachecontrol)
+        resp.headers.setdefault("Pragma", self.pragma)
+        resp.headers.setdefault("Expires", self.expires)
+        return resp
+
+    async def get_response(self, path: str, scope: Scope) -> Response:
+        """
+        Override get_response to implement SPA routing.
+
+        When a file is not found and html mode is enabled, serve index.html instead of raising a 404.
+        This allows client-side routing to work correctly in SPAs.
+        """
+        try:
+            return await super().get_response(path, scope)
+        except HTTPException as exc:
+            # If the file is not found (404) and html mode is enabled, serve index.html
+            # This allows client-side routing to handle the path
+            if exc.status_code == 404 and self.html:
+                return await super().get_response("index.html", scope)
+            raise