Add Support For Custom JSON Encoders/Decoders

eel/__init__.py

@@ -1,7 +1,7 @@
 from builtins import range
 import traceback
 from io import open
-from typing import Union, Any, Dict, List, Set, Tuple, Optional, Callable, TYPE_CHECKING
+from typing import Union, Any, Dict, List, Set, Tuple, Optional, Callable, TYPE_CHECKING, cast, Type
 
 if TYPE_CHECKING:
     from eel.types import OptionsDictT, WebSocketT
@@ -28,6 +28,7 @@
 mimetypes.add_type('application/javascript', '.js')
 _eel_js_file: str = pkg.resource_filename('eel', 'eel.js')
 _eel_js: str = open(_eel_js_file, encoding='utf-8').read()
+_eel_json_dumps_default_function: Callable[[Any], Any] = lambda o: None
 _websockets: List[Tuple[Any, WebSocketT]] = []
 _call_return_values: Dict[Any, Any] = {}
 _call_return_callbacks: Dict[float, Tuple[Callable[..., Any], Optional[Callable[..., Any]]]] = {}
@@ -55,6 +56,8 @@
     'position':         None,                       # (left, top) of main window
     'geometry':         {},                         # Dictionary of size/position for all windows
     'close_callback':   None,                       # Callback for when all windows have closed
+    'json_encoder':     None,                       # Custom JSONEncoder to customize json data dumping
+    'json_decoder':     None,                       # Custom JSONDecoder to customize json data loading
     'app_mode':  True,                              # (Chrome specific option)
     'all_interfaces': False,                        # Allow bottle server to listen for connections on all interfaces
     'disable_cache': True,                          # Sets the no-store response header when serving assets
@@ -223,7 +226,7 @@ def _eel() -> str:
     page = _eel_js.replace('/** _py_functions **/',
                            '_py_functions: %s,' % list(_exposed_functions.keys()))
     page = page.replace('/** _start_geometry **/',
-                        '_start_geometry: %s,' % _safe_json(start_geometry))
+                        '_start_geometry: %s,' % _safe_json_dumps(start_geometry))
     btl.response.content_type = 'application/javascript'
     _set_response_headers(btl.response)
     return page
@@ -259,15 +262,15 @@ def _websocket(ws: WebSocketT) -> None:
     page = btl.request.query.page
     if page not in _mock_queue_done:
         for call in _mock_queue:
-            _repeated_send(ws, _safe_json(call))
+            _repeated_send(ws, _safe_json_dumps(call))
         _mock_queue_done.add(page)
 
     _websockets += [(page, ws)]
 
     while True:
         msg = ws.receive()
         if msg is not None:
-            message = jsn.loads(msg)
+            message = _safe_json_loads(msg)
             spawn(_process_message, message, ws)
         else:
             _websockets.remove((page, ws))
@@ -298,8 +301,12 @@ def register_eel_routes(app: btl.Bottle) -> None:
 
 # Private functions
 
-def _safe_json(obj: Any) -> str:
-    return jsn.dumps(obj, default=lambda o: None)
+def _safe_json_loads(obj: str) -> Any:
+    return jsn.loads(obj, cls=cast(Optional[Type[jsn.JSONDecoder]], _start_args['json_decoder']))
+
+def _safe_json_dumps(obj: Any) -> str:
+    return jsn.dumps(obj, cls=cast(Optional[Type[jsn.JSONEncoder]], _start_args['json_encoder']),
+                     default=_eel_json_dumps_default_function if not _start_args['json_encoder'] else None)
 
 
 def _repeated_send(ws: WebSocketT, msg: str) -> None:
@@ -324,7 +331,7 @@ def _process_message(message: Dict[str, Any], ws: WebSocketT) -> None:
             status = 'error'
             error_info['errorText'] = repr(e)
             error_info['errorTraceback'] = err_traceback
-        _repeated_send(ws, _safe_json({ 'return': message['call'],
+        _repeated_send(ws, _safe_json_dumps({ 'return': message['call'],
                                         'status': status,
                                         'value': return_val,
                                         'error': error_info,}))
@@ -375,7 +382,7 @@ def _mock_call(name: str, args: Any) -> Callable[[Optional[Callable[..., Any]],
 def _js_call(name: str, args: Any) -> Callable[[Optional[Callable[..., Any]], Optional[Callable[..., Any]]], Any]:
     call_object = _call_object(name, args)
     for _, ws in _websockets:
-        _repeated_send(ws, _safe_json(call_object))
+        _repeated_send(ws, _safe_json_dumps(call_object))
     return _call_return(call_object)
 
 
@@ -409,7 +416,7 @@ def _detect_shutdown() -> None:
 def _websocket_close(page: str) -> None:
     global _shutdown
 
-    close_callback = _start_args.get('close_callback')
+    close_callback = cast(Callable[..., Any], _start_args.get('close_callback'))
 
     if close_callback is not None:
         if not callable(close_callback):

eel/types.py

@@ -1,4 +1,4 @@
-from typing import Union, Dict, List, Tuple, Callable, Optional, Any, TYPE_CHECKING
+from typing import Union, Dict, List, Tuple, Callable, Optional, Any, TYPE_CHECKING, Type
 
 # This business is slightly awkward, but needed for backward compatibility,
 # because Python < 3.7 doesn't have __future__/annotations, and <3.10 doesn't
@@ -12,17 +12,20 @@
         JinjaEnvironmentT = Environment # type: ignore
     from geventwebsocket.websocket import WebSocket
     WebSocketT = WebSocket
+    from json import JSONDecoder, JSONEncoder
 else:
     JinjaEnvironmentT = None
     WebSocketT = Any
+    JSONEncoder = Any
+    JSONDecoder = Any
 
 OptionsDictT = Dict[
         str,
         Optional[
             Union[
                 str, bool, int, float,
                 List[str], Tuple[int, int], Dict[str, Tuple[int, int]],
-                Callable[..., Any], JinjaEnvironmentT
+                Callable[..., Any], JinjaEnvironmentT, Type[JSONEncoder], Type[JSONDecoder]
             ]
         ]
     ]

examples/10 - custom_json_encoder_decoder/.gitignore

@@ -0,0 +1 @@
+node_modules

examples/10 - custom_json_encoder_decoder/custom_json_encoder_decoder.py

@@ -0,0 +1,48 @@
+import eel
+import json
+import datetime
+
+eel.init('web')
+
+@eel.expose
+def py_json_data_sender():
+    return {
+        'datetime': datetime.datetime.now()
+    }
+
+@eel.expose
+def py_json_data_loader():
+    return eel.js_json_data_sender()(print_value)
+
+def print_value(v):
+    print('Got this value from javascript:')
+    print(v)
+
+# Custom Json Encoder.
+class EelJsonEncoder(json.JSONEncoder):
+    def default(self, o):
+        if isinstance(o, datetime.date):
+            return o.__str__()
+
+
+# Custom Json Decoder.
+class CustomDatetimeObj(object):
+    def __init__(self, datetime):
+        self.datetime = datetime
+
+    def __str__(self):
+        return 'CustomDatetimeObj: %s' % self.datetime.__str__()
+
+def decoder_object_hook(o):
+    if 'datetime' in o:
+        return CustomDatetimeObj(datetime=o['datetime'])
+    else:
+        return o
+
+class EelJsonDecoder(json.JSONDecoder):
+    def __init__(self, object_hook=decoder_object_hook, *args, **kwargs):
+        super().__init__(object_hook=object_hook, *args, **kwargs)
+
+
+eel.start('custom_json_encoder_decoder.html', json_encoder=EelJsonEncoder,
+          json_decoder=EelJsonDecoder, size=(400, 300))

examples/10 - custom_json_encoder_decoder/web/custom_json_encoder_decoder.html

@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <title>Custom JSON Encoder/Decoder Eel Example</title>
+
+        <!-- Include eel.js - note this file doesn't exist in the 'web' directory -->
+        <script type="text/javascript" src="/eel.js"></script>
+        <script type="text/javascript" src="custom_json_encoder_decoder.js"></script>
+    </head>
+
+    <body>
+        Hello World!
+    </body>
+</html>

examples/10 - custom_json_encoder_decoder/web/custom_json_encoder_decoder.js

@@ -0,0 +1,17 @@
+eel.expose(js_json_data_sender);
+function js_json_data_sender() {
+    return {
+        datetime: new Date()
+    }
+}
+
+function print_value(v) {
+    console.log('Got this value from python:');
+    console.log(v);
+}
+
+// Call Python function.
+eel.py_json_data_sender()(print_value);
+
+// Call JS function from python.
+eel.py_json_data_loader();