Add proper type overload to determine handle_exception return type

lib/galaxy/web/framework/middleware/error.py

@@ -16,6 +16,7 @@
 from typing import (
     cast,
     Optional,
+    overload,
 )
 
 import markupsafe
@@ -28,6 +29,7 @@
     formatter,
     reporter,
 )
+from typing_extensions import Literal
 
 log = logging.getLogger(__name__)
 
@@ -191,7 +193,7 @@ def make_catching_iter(self, app_iter, environ, sr_checker):
             return app_iter
         return CatchingIter(app_iter, environ, sr_checker, self)
 
-    def exception_handler(self, exc_info, environ) -> Optional[str]:
+    def exception_handler(self, exc_info, environ) -> str:
         simple_html_error = False
         if self.xmlhttp_key:
             get_vars = wsgilib.parse_querystring(environ)
@@ -348,10 +350,54 @@ def extraData(self):
     }
 
 
+@overload
 def handle_exception(
     exc_info,
     error_stream,
-    html=True,
+    html: Literal[False] = ...,
+    debug_mode=...,
+    error_email=...,
+    error_log=...,
+    show_exceptions_in_wsgi_errors=...,
+    error_email_from=...,
+    smtp_server=...,
+    smtp_username=...,
+    smtp_password=...,
+    smtp_use_tls=...,
+    error_subject_prefix=...,
+    error_message=...,
+    simple_html_error=...,
+    environ=...,
+) -> None:
+    ...
+
+
+@overload
+def handle_exception(
+    exc_info,
+    error_stream,
+    html: Literal[True] = ...,
+    debug_mode=...,
+    error_email=...,
+    error_log=...,
+    show_exceptions_in_wsgi_errors=...,
+    error_email_from=...,
+    smtp_server=...,
+    smtp_username=...,
+    smtp_password=...,
+    smtp_use_tls=...,
+    error_subject_prefix=...,
+    error_message=...,
+    simple_html_error=...,
+    environ=...,
+) -> str:
+    ...
+
+
+def handle_exception(
+    exc_info,
+    error_stream,
+    html: bool = True,
     debug_mode=False,
     error_email=None,
     error_log=None,