from typing import Any, Mapping
def prepend_root_path(scope: Mapping[str, Any], path: str) -> str:
"""
Prepends the ASGI root path to the given path if one is configured.
Normalizes the input path by ensuring it has a leading slash and removing
trailing slashes. The root path is already normalized by get_root_path().
Args:
scope: The ASGI scope dictionary containing the root_path key
path: The path to prepend the root path to (e.g., "/login", "logout")
Returns:
The normalized path with root path prepended if configured,
otherwise just the normalized path. Never has a trailing slash
except when the result is just "/".
Examples:
With root_path="/apps/phoenix":
- prepend_root_path(request.scope, "/login") -> "/apps/phoenix/login"
- prepend_root_path(request.scope, "login") -> "/apps/phoenix/login"
- prepend_root_path(request.scope, "/") -> "/apps/phoenix"
- prepend_root_path(request.scope, "") -> "/apps/phoenix"
- prepend_root_path(request.scope, "login/") -> "/apps/phoenix/login"
- prepend_root_path(request.scope, "/login/") -> "/apps/phoenix/login"
- prepend_root_path(request.scope, "abc/def/") -> "/apps/phoenix/abc/def"
With no root_path:
- prepend_root_path(request.scope, "/login") -> "/login"
- prepend_root_path(request.scope, "login") -> "/login"
- prepend_root_path(request.scope, "/") -> "/"
- prepend_root_path(request.scope, "") -> "/"
- prepend_root_path(request.scope, "login/") -> "/login"
- prepend_root_path(request.scope, "/login/") -> "/login"
- prepend_root_path(request.scope, "abc/def/") -> "/abc/def"
"""
path = path if path.startswith("/") else f"/{path}"
path = path.rstrip("/") or "/"
root_path = get_root_path(scope)
if path == "/":
return root_path or "/"
return f"{root_path}{path}"
def get_root_path(scope: Mapping[str, Any]) -> str:
"""
Extracts and normalizes the root path from the ASGI scope.
The root path is typically set by reverse proxies or when the application
is mounted at a sub-path (e.g., "/apps/phoenix" when behind a proxy).
If present, ensures the path has a leading slash and removes trailing slashes.
Args:
scope: The ASGI scope dictionary containing the root_path key
Returns:
The normalized root path as a string (with leading slash, no trailing slash)
if configured, otherwise empty string.
Examples:
- Behind proxy at "/apps/phoenix": returns "/apps/phoenix"
- Missing leading slash "apps/phoenix": returns "/apps/phoenix"
- With trailing slash "/apps/phoenix/": returns "/apps/phoenix"
- Direct deployment: returns ""
- None in scope: returns ""
"""
root_path = str(scope.get("root_path") or "")
if not root_path:
return ""
if not root_path.startswith("/"):
root_path = f"/{root_path}"
return root_path.rstrip("/")
