Add hooks to send email when uncaught exception occurs

wuttapos/app.py

@@ -25,7 +25,13 @@ WuttaPOS app
 """
 
 import json
+import logging
 import os
+import socket
+import sys
+import threading
+from collections import OrderedDict
+from traceback import format_exception
 
 from rattail import app as base
 from rattail.config import make_config
@@ -37,6 +43,9 @@ import wuttapos
 from wuttapos.util import get_pos_batch_handler
 
 
+log = logging.getLogger(__name__)
+
+
 class WuttaAppHandler(base.AppHandler):
     """
     Custom app handler for WuttaPOS
@@ -55,6 +64,61 @@ def main(page: ft.Page):
     config = make_config()
     app = config.get_app()
     model = app.model
+    handler = get_pos_batch_handler(config)
+
+    # nb. as of python 3.10 the original hook is accessible, we needn't save the ref
+    # cf. https://docs.python.org/3/library/threading.html#threading.__excepthook__
+    orig_thread_hook = threading.excepthook
+
+    hostname = socket.gethostname()
+    email_context = OrderedDict([
+        ('hostname', hostname),
+        ('ipaddress', socket.gethostbyname(hostname)),
+        ('terminal', handler.get_terminal_id() or '??'),
+    ])
+
+    def send_error_email(traceback):
+        extra_context = OrderedDict(email_context)
+
+        try:
+            uuid = page.session.get('user_uuid')
+            if uuid:
+                session = app.make_session()
+                user = session.get(model.User, uuid)
+                extra_context['username'] = user.username
+                batch = handler.get_current_batch(user, create=False)
+                if batch:
+                    extra_context['batchid'] = batch.id_str
+                session.close()
+            else:
+                extra_context['username'] = 'n/a'
+
+            app.send_email('uncaught_exception', {
+                'extra_context': extra_context,
+                'traceback': traceback,
+            })
+
+        except:
+            log.exception("failed to send error email")
+
+    def sys_exc_hook(exc_type, exc_value, exc_traceback):
+        traceback = ''.join(format_exception(exc_type, exc_value, exc_traceback)).strip()
+        send_error_email(traceback)
+        sys.__excepthook__(exc_type, exc_value, exc_traceback)
+
+    def thread_exc_hook(args):
+        traceback = ''.join(format_exception(args.exc_type, args.exc_value, args.exc_traceback)).strip()
+        send_error_email(traceback)
+        orig_thread_hook(args)
+
+    # custom exception hook for main process
+    sys.excepthook = sys_exc_hook
+
+    # custom exception hook for threads (requires python 3.8)
+    # cf. https://docs.python.org/3/library/threading.html#threading.excepthook
+    v = sys.version_info
+    if v.major >= 3 and v.minor >= 8:
+        threading.excepthook = thread_exc_hook
 
     page.title = f"WuttaPOS v{wuttapos.__version__}"
     page.window_full_screen = True
@@ -137,7 +201,6 @@ def main(page: ft.Page):
             if user:
                 page.session.set('user_uuid', uuid)
                 page.session.set('user_display', str(user))
-                handler = get_pos_batch_handler(config)
                 batch = handler.get_current_batch(user, create=False)
                 if batch:
                     page.session.set('txn_display', batch.id_str)

wuttapos/views/pos.py

@@ -657,7 +657,7 @@ class POSView(WuttaView):
         meta_button_width = meta_button_height * 2
         meta_font_size = tenkey_font_size
 
-        def meta_button(text, on_click=None, bgcolor='blue'):
+        def meta_button(text, on_click=None, bgcolor='blue', data=None):
             return ft.Container(content=ft.Text(text, size=meta_font_size,
                                                 weight=ft.FontWeight.BOLD),
                                 height=meta_button_height,
@@ -666,7 +666,8 @@ class POSView(WuttaView):
                                 alignment=ft.alignment.center,
                                 border=ft.border.all(1, 'black'),
                                 border_radius=ft.border_radius.all(5),
-                                bgcolor=bgcolor)
+                                bgcolor=bgcolor,
+                                data=data)
 
         self.meta_menu = ft.Container(
             content=ft.Column(
@@ -695,7 +696,8 @@ class POSView(WuttaView):
                     ft.Row(
                         [
                             meta_button("TODO", bgcolor='blue', on_click=self.not_supported),
-                            meta_button("TODO", bgcolor='blue', on_click=self.not_supported),
+                            meta_button("TODO", bgcolor='blue', on_click=self.not_supported,
+                                        data={'error': True}),
                         ],
                         spacing=0,
                     ),
@@ -867,6 +869,11 @@ class POSView(WuttaView):
         self.page.update()
 
     def not_supported(self, e=None, feature=None):
+
+        # test error handler
+        if e.control.data and e.control.data.get('error'):
+            raise ValueError("NOT YET SUPPORTED")
+
         text = "NOT YET SUPPORTED"
         if not feature and e:
             feature = e.control.content.value