changes to make app.current_request thread safe when running chalice …

…locally

- fixes race conditions that can occur when chalice is being run locally
  and it handling multiple concurrent requests

chalice/local.py

@@ -16,7 +16,16 @@
 from six.moves.BaseHTTPServer import HTTPServer
 from six.moves.BaseHTTPServer import BaseHTTPRequestHandler
 from six.moves.socketserver import ThreadingMixIn
-from typing import List, Any, Dict, Tuple, Callable, Optional, Union  # noqa
+from typing import (
+    List,
+    Any,
+    Dict,
+    Tuple,
+    Callable,
+    Optional,
+    Union,
+    cast,
+)  # noqa
 
 from chalice.app import Chalice  # noqa
 from chalice.app import CORSConfig  # noqa
@@ -47,7 +56,10 @@ def time(self):
 
 def create_local_server(app_obj, config, host, port):
     # type: (Chalice, Config, str, int) -> LocalDevServer
-    return LocalDevServer(app_obj, config, host, port)
+    local_app_opj = cast(LocalChalice, app_obj)  # type: LocalChalice
+    local_app_opj.__class__ = LocalChalice
+    local_app_opj.initialize_current_request_lookup()
+    return LocalDevServer(local_app_opj, config, host, port)
 
 
 class LocalARNBuilder(object):
@@ -661,3 +673,28 @@ def shutdown(self):
         # type: () -> None
         if self._server is not None:
             self._server.shutdown()
+
+
+class LocalChalice(Chalice):
+    def __init__(self, *args, **kwargs):
+        # type: (Any, Any) -> None
+        self._current_request_lookup = {}  # type: Dict[int, Optional[Request]]
+        super(LocalChalice, self).__init__(*args, **kwargs)
+
+    def initialize_current_request_lookup(self):
+        # type: () -> None
+        self._current_request_lookup = {}
+
+    @property
+    def current_request(self):  # noqa
+        # type: () -> Optional[Request]
+        thread_id = threading.current_thread().ident
+        assert thread_id is not None
+        return self._current_request_lookup.get(thread_id, None)
+
+    @current_request.setter
+    def current_request(self, value):  # noqa
+        # type: (Optional[Request]) -> None
+        thread_id = threading.current_thread().ident
+        assert thread_id is not None
+        self._current_request_lookup[thread_id] = value