Python exceptions can now be handled via QML

callCoro/callBackendCoro can now take onSuccess(result) and
onError(type, args, errorObject) callbacks.

src/python/app.py

@@ -61,9 +61,17 @@ class App:
 
 
     def _call_coro(self, coro: Coroutine, uuid: str) -> None:
-        self.run_in_loop(coro).add_done_callback(
+        def on_done(future: Future) -> None:
-            lambda future: CoroutineDone(uuid=uuid, result=future.result()),
+            try:
-        )
+                result    = future.result()
+                exception = None
+            except Exception as err:
+                result    = None
+                exception = err
+
+            CoroutineDone(uuid, result, exception)
+
+        self.run_in_loop(coro).add_done_callback(on_done)
 
 
     def call_backend_coro(self, name: str, uuid: str, args: Sequence[str] = (),

src/python/pyotherside_events.py

@@ -1,6 +1,6 @@
 from dataclasses import dataclass, field
 from enum import Enum
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, List, Optional, Union
 
 import pyotherside
 
@@ -47,8 +47,9 @@ class AlertRequested(PyOtherSideEvent):
 class CoroutineDone(PyOtherSideEvent):
     """Indicate that an asyncio coroutine finished."""
 
-    uuid:   str = field()
+    uuid:   str                    = field()
-    result: Any = None
+    result: Any                    = None
+    exception: Optional[Exception] = None
 
 
 @dataclass

src/qml/Python.qml

@@ -14,18 +14,20 @@ Python {
         return call_sync("APP.backend." + name, args)
     }
 
-    function callCoro(name, args=[], callback=null) {
+    function callCoro(name, args=[], onSuccess=null, onError=null) {
         let uuid = Math.random() + "." + name
 
-        pendingCoroutines[uuid] = callback || function() {}
+        pendingCoroutines[uuid] = {onSuccess, onError}
         call("APP.call_backend_coro", [name, uuid, args])
     }
 
-    function callClientCoro(accountId, name, args=[], callback=null) {
+    function callClientCoro(
+        accountId, name, args=[], onSuccess=null, onError=null
+    ) {
         callCoro("wait_until_client_exists", [accountId], () => {
             let uuid = Math.random() + "." + name
 
-            pendingCoroutines[uuid] = callback || function() {}
+            pendingCoroutines[uuid] = {onSuccess, onError}
             call("APP.call_client_coro", [accountId, name, uuid, args])
         })
     }

src/qml/event_handlers.js

@@ -13,8 +13,20 @@ function onAlertRequested() {
 }
 
 
-function onCoroutineDone(uuid, result) {
+function onCoroutineDone(uuid, result, error) {
-    py.pendingCoroutines[uuid](result)
+    let onSuccess = py.pendingCoroutines[uuid].onSuccess
+    let onError   = py.pendingCoroutines[uuid].onError
+
+    if (error) {
+        let type = py.getattr(py.getattr(error, "__class__"), "__name__")
+        let args = py.getattr(error, "args")
+
+        onError ?
+        onError(type, args, error) :
+        console.error(uuid + ": " + type + ": " + args)
+
+    } else if (onSuccess) { onSuccess(result) }
+
     delete pendingCoroutines[uuid]
 }