Raise a Waitress exception into the UI with a modal dialog and reset the share if it occurs

cli/onionshare_cli/web/web.py

@@ -57,6 +57,12 @@ except Exception:
     pass
 
 
+class WaitressException(Exception):
+    """
+    There was a problem starting the waitress web server.
+    """
+
+
 class Web:
     """
     The Web object is the OnionShare web server, powered by flask
@@ -349,14 +355,17 @@ class Web:
         if self.mode == "chat":
             self.socketio.run(self.app, host=host, port=port)
         else:
-            self.waitress = create_server(
-                self.app,
-                host=host,
-                port=port,
-                clear_untrusted_proxy_headers=True,
-                ident="OnionShare",
-            )
-            self.waitress.run()
+            try:
+                self.waitress = create_server(
+                    self.app,
+                    host=host,
+                    port=port,
+                    clear_untrusted_proxy_headers=True,
+                    ident="OnionShare",
+                )
+                self.waitress.run()
+            except Exception as e:
+                raise WaitressException(f"Error starting Waitress: {e}")
 
     def stop(self, port):
         """
@@ -389,7 +398,6 @@ class Web:
     def waitress_custom_shutdown(self):
         """Shutdown the Waitress server immediately"""
         # Code borrowed from https://github.com/Pylons/webtest/blob/4b8a3ebf984185ff4fefb31b4d0cf82682e1fcf7/webtest/http.py#L93-L104
-        self.waitress.was_shutdown = True
         while self.waitress._map:
             triggers = list(self.waitress._map.values())
             for trigger in triggers:

desktop/onionshare/gui_common.py

@@ -41,7 +41,7 @@ from onionshare_cli.onion import (
     PortNotAvailable,
 )
 from onionshare_cli.meek import Meek
-
+from onionshare_cli.web.web import WaitressException
 
 class GuiCommon:
     """
@@ -581,6 +581,13 @@ class GuiCommon:
             return strings._("error_port_not_available")
         return None
 
+    @staticmethod
+    def get_translated_web_error(e):
+        """
+        Takes an exception defined in web.py and returns a translated error message
+        """
+        if type(e) is WaitressException:
+            return strings._("waitress_web_server_error")
 
 class ToggleCheckbox(QtWidgets.QCheckBox):
     def __init__(self, text):

desktop/onionshare/resources/locale/en.json

@@ -252,5 +252,6 @@
     "moat_bridgedb_error": "Could not contact BridgeDB.",
     "moat_captcha_error": "Incorrect solution. Please try again.",
     "moat_solution_empty_error": "Enter the characters from the image",
-    "mode_tor_not_connected_label": "OnionShare is not connected to the Tor network"
+    "mode_tor_not_connected_label": "OnionShare is not connected to the Tor network",
+    "waitress_web_server_error": "There was a problem starting the web server"
 }

desktop/onionshare/tab/mode/__init__.py

@@ -27,7 +27,7 @@ from .mode_settings_widget import ModeSettingsWidget
 
 from ..server_status import ServerStatus
 from ... import strings
-from ...threads import OnionThread, AutoStartTimer
+from ...threads import OnionThread, WebThread, AutoStartTimer
 from ...widgets import Alert, MinimumSizeWidget
 
 
@@ -294,6 +294,8 @@ class Mode(QtWidgets.QWidget):
             self.onion_thread.success.connect(self.starting_server_step2.emit)
             self.onion_thread.success_early.connect(self.starting_server_early.emit)
             self.onion_thread.error.connect(self.starting_server_error.emit)
+            self.web_thread = WebThread(self)
+            self.web_thread.error.connect(self.starting_server_error.emit)
             self.onion_thread.start()
 
     def start_scheduled_service(self, obtain_onion_early=False):

desktop/onionshare/threads.py

@@ -39,6 +39,8 @@ from onionshare_cli.onion import (
     PortNotAvailable,
 )
 
+from onionshare_cli.web.web import WaitressException
+
 from . import strings
 
 
@@ -83,7 +85,6 @@ class OnionThread(QtCore.QThread):
                 # wait for modules in thread to load, preventing a thread-related cx_Freeze crash
                 time.sleep(0.2)
                 # start onionshare http service in new thread
-                self.mode.web_thread = WebThread(self.mode)
                 self.mode.web_thread.start()
                 self.success.emit()
 
@@ -122,9 +123,14 @@ class WebThread(QtCore.QThread):
 
     def run(self):
         self.mode.common.log("WebThread", "run")
-        self.mode.web.start(self.mode.app.port)
-        self.success.emit()
-
+        try:
+            self.mode.web.start(self.mode.app.port)
+            self.success.emit()
+        except WaitressException as e:
+            message = self.mode.common.gui.get_translated_web_error(e)
+            self.mode.common.log("WebThread", "run", message)
+            self.error.emit(message)
+            return
 
 class AutoStartTimer(QtCore.QThread):
     """