From 49e8eeecdd53557a62445768b702cbc407157b56 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Mon, 19 Feb 2024 17:42:09 +0100
Subject: [PATCH 01/14] added custom exception handler

---
 reflex/app.py              |  3 ++-
 reflex/state.py            | 15 ++++++++++++++-
 reflex/utils/exceptions.py |  8 ++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/reflex/app.py b/reflex/app.py
index 7ab4b5abe0..34e9533285 100644
--- a/reflex/app.py
+++ b/reflex/app.py
@@ -141,7 +141,7 @@ class App(Base):
     # The radix theme for the entire app
     theme: Optional[Component] = themes.theme(accent_color="blue")
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, exception_handler = None, *args, **kwargs):
         """Initialize the app.
 
         Args:
@@ -158,6 +158,7 @@ def __init__(self, *args, **kwargs):
                 "`connect_error_component` is deprecated, use `overlay_component` instead"
             )
         super().__init__(*args, **kwargs)
+        BaseState.set_exception_handler(exception_handler)
         state_subclasses = BaseState.__subclasses__()
         is_testing_env = constants.PYTEST_CURRENT_TEST in os.environ
 
diff --git a/reflex/state.py b/reflex/state.py
index 33ff12c177..d41173501a 100644
--- a/reflex/state.py
+++ b/reflex/state.py
@@ -213,6 +213,18 @@ class BaseState(Base, ABC, extra=pydantic.Extra.allow):
     # The router data for the current page
     router: RouterData = RouterData()
 
+    # Custom exception hanlder
+    _exception_handler = None
+
+    @classmethod
+    def set_exception_handler(cls, exception_handler):
+        cls._exception_handler = exception_handler
+
+    @classmethod
+    def _handle_exception(cls, exception):
+        if cls._exception_handler:
+            cls._exception_handler(exception)
+
     def __init__(self, *args, parent_state: BaseState | None = None, **kwargs):
         """Initialize the state.
 
@@ -1192,7 +1204,8 @@ async def _process_event(
         # If an error occurs, throw a window alert.
         except Exception:
             error = traceback.format_exc()
-            print(error)
+            # print(error)
+            BaseState._handle_exception(error)
             yield state._as_state_update(
                 handler,
                 window_alert("An error occurred. See logs for details."),
diff --git a/reflex/utils/exceptions.py b/reflex/utils/exceptions.py
index e4a9a6e6c9..63ab9cecae 100644
--- a/reflex/utils/exceptions.py
+++ b/reflex/utils/exceptions.py
@@ -19,3 +19,11 @@ class MatchTypeError(TypeError):
     """Raised when the return types of match cases are different."""
 
     pass
+
+class ExceptionHandler:
+    @staticmethod
+    def handle_exception(exception_handler, exception):
+        if exception_handler:
+            exception_handler(exception)
+        else:
+            print(exception)
\ No newline at end of file

From 8082062768e4581bd1a00a68a0650cd4431420e2 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Mon, 19 Feb 2024 17:45:01 +0100
Subject: [PATCH 02/14] added comment in exceptions.py

---
 reflex/utils/exceptions.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/reflex/utils/exceptions.py b/reflex/utils/exceptions.py
index 63ab9cecae..209cde3d6b 100644
--- a/reflex/utils/exceptions.py
+++ b/reflex/utils/exceptions.py
@@ -21,6 +21,8 @@ class MatchTypeError(TypeError):
     pass
 
 class ExceptionHandler:
+    ''' this is another idea i thought of making an exception handler class. state.py and app.py 
+    will use it to handle exception during event handling '''
     @staticmethod
     def handle_exception(exception_handler, exception):
         if exception_handler:

From 81df28596cf24df4ac046e9df249c4c76532c417 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 20 Feb 2024 11:02:33 +0100
Subject: [PATCH 03/14] exception_handler added as rx.App attribute

---
 reflex/app.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/reflex/app.py b/reflex/app.py
index 34e9533285..7dcca21f01 100644
--- a/reflex/app.py
+++ b/reflex/app.py
@@ -141,7 +141,10 @@ class App(Base):
     # The radix theme for the entire app
     theme: Optional[Component] = themes.theme(accent_color="blue")
 
-    def __init__(self, exception_handler = None, *args, **kwargs):
+    # Custom exception handler
+    exception_handler: Optional[Callable] = None
+
+    def __init__(self, *args, **kwargs):
         """Initialize the app.
 
         Args:
@@ -158,7 +161,6 @@ def __init__(self, exception_handler = None, *args, **kwargs):
                 "`connect_error_component` is deprecated, use `overlay_component` instead"
             )
         super().__init__(*args, **kwargs)
-        BaseState.set_exception_handler(exception_handler)
         state_subclasses = BaseState.__subclasses__()
         is_testing_env = constants.PYTEST_CURRENT_TEST in os.environ
 

From 56044543f7422f6374f91c4d34bc2abc3e6aa933 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 20 Feb 2024 11:05:19 +0100
Subject: [PATCH 04/14] app instance is used to get exception_handler and
 default behavior of exception is added

---
 reflex/state.py | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/reflex/state.py b/reflex/state.py
index d41173501a..498a31af5f 100644
--- a/reflex/state.py
+++ b/reflex/state.py
@@ -213,18 +213,6 @@ class BaseState(Base, ABC, extra=pydantic.Extra.allow):
     # The router data for the current page
     router: RouterData = RouterData()
 
-    # Custom exception hanlder
-    _exception_handler = None
-
-    @classmethod
-    def set_exception_handler(cls, exception_handler):
-        cls._exception_handler = exception_handler
-
-    @classmethod
-    def _handle_exception(cls, exception):
-        if cls._exception_handler:
-            cls._exception_handler(exception)
-
     def __init__(self, *args, parent_state: BaseState | None = None, **kwargs):
         """Initialize the state.
 
@@ -1204,8 +1192,12 @@ async def _process_event(
         # If an error occurs, throw a window alert.
         except Exception:
             error = traceback.format_exc()
-            # print(error)
-            BaseState._handle_exception(error)
+            app = getattr(prerequisites.get_app(), constants.CompileVars.APP) 
+            exception_handler = app.exception_handler    
+            if callable(exception_handler):
+                exception_handler(error)
+            else:
+                print(error)
             yield state._as_state_update(
                 handler,
                 window_alert("An error occurred. See logs for details."),

From a0382ac71237464c8ec92e6da5b136f9748511ca Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 20 Feb 2024 11:10:38 +0100
Subject: [PATCH 05/14] added exception_handler for rx.call_script() for client
 side exception handling

---
 reflex/event.py | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/reflex/event.py b/reflex/event.py
index 499b4877a6..2ed2952d36 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -641,12 +641,14 @@ def _callback_arg_spec(eval_result):
 def call_script(
     javascript_code: str,
     callback: EventHandler | Callable | None = None,
+    exception_handler: callable | None = None
 ) -> EventSpec:
     """Create an event handler that executes arbitrary javascript code.
 
     Args:
         javascript_code: The code to execute.
         callback: EventHandler that will receive the result of evaluating the javascript code.
+        exception_handler: User-defined exception handler
 
     Returns:
         EventSpec: An event that will execute the client side javascript.
@@ -666,12 +668,19 @@ def call_script(
         callback_kwargs = {
             "callback": f"({arg_name}) => queueEvents([{format.format_event(event_spec)}], {constants.CompileVars.SOCKET})"
         }
-    return server_side(
-        "_call_script",
-        get_fn_signature(call_script),
-        javascript_code=javascript_code,
-        **callback_kwargs,
-    )
+
+    try:
+        return server_side(
+            "_call_script",
+            get_fn_signature(call_script),
+            javascript_code=javascript_code,
+            **callback_kwargs,
+        )
+    except Exception as client_error:
+        if exception_handler and callable(exception_handler):
+            exception_handler(client_error)
+        else:
+            raise client_error
 
 
 def get_event(state, event):

From 047b283246f5400d8b23c624c6319d9de7a297a2 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 20 Feb 2024 11:16:02 +0100
Subject: [PATCH 06/14] ExceptionHandler class removed from exceptions.py

---
 reflex/utils/exceptions.py | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/reflex/utils/exceptions.py b/reflex/utils/exceptions.py
index 209cde3d6b..e4a9a6e6c9 100644
--- a/reflex/utils/exceptions.py
+++ b/reflex/utils/exceptions.py
@@ -19,13 +19,3 @@ class MatchTypeError(TypeError):
     """Raised when the return types of match cases are different."""
 
     pass
-
-class ExceptionHandler:
-    ''' this is another idea i thought of making an exception handler class. state.py and app.py 
-    will use it to handle exception during event handling '''
-    @staticmethod
-    def handle_exception(exception_handler, exception):
-        if exception_handler:
-            exception_handler(exception)
-        else:
-            print(exception)
\ No newline at end of file

From 4613033bbc5ca929e7c0bcebe00bd4dfacd1067b Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 20 Feb 2024 16:47:32 +0100
Subject: [PATCH 07/14] removed exception handler from call_script and
 try/catch added to catch frontend exception

---
 reflex/event.py | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/reflex/event.py b/reflex/event.py
index 2ed2952d36..243a311af1 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -641,7 +641,6 @@ def _callback_arg_spec(eval_result):
 def call_script(
     javascript_code: str,
     callback: EventHandler | Callable | None = None,
-    exception_handler: callable | None = None
 ) -> EventSpec:
     """Create an event handler that executes arbitrary javascript code.
 
@@ -668,19 +667,23 @@ def call_script(
         callback_kwargs = {
             "callback": f"({arg_name}) => queueEvents([{format.format_event(event_spec)}], {constants.CompileVars.SOCKET})"
         }
+    wrapped_code = f"""
+        try {{
+            {javascript_code}
+        }} catch (error) {{
+            queueEvents([{window_alert("'An error occurred. See logs for details.'")}], {constants.CompileVars.SOCKET});
+        }}
+    """
+
 
-    try:
-        return server_side(
+  
+    return server_side(
             "_call_script",
             get_fn_signature(call_script),
-            javascript_code=javascript_code,
+            javascript_code=wrapped_code,
             **callback_kwargs,
         )
-    except Exception as client_error:
-        if exception_handler and callable(exception_handler):
-            exception_handler(client_error)
-        else:
-            raise client_error
+
 
 
 def get_event(state, event):

From bc72f196815709b0662e6c17ea0f058eb17a0c9f Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Thu, 22 Feb 2024 13:47:32 +0100
Subject: [PATCH 08/14] wrapped_code removed

---
 reflex/event.py | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/reflex/event.py b/reflex/event.py
index 243a311af1..3d98f5ee03 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -647,7 +647,6 @@ def call_script(
     Args:
         javascript_code: The code to execute.
         callback: EventHandler that will receive the result of evaluating the javascript code.
-        exception_handler: User-defined exception handler
 
     Returns:
         EventSpec: An event that will execute the client side javascript.
@@ -667,25 +666,15 @@ def call_script(
         callback_kwargs = {
             "callback": f"({arg_name}) => queueEvents([{format.format_event(event_spec)}], {constants.CompileVars.SOCKET})"
         }
-    wrapped_code = f"""
-        try {{
-            {javascript_code}
-        }} catch (error) {{
-            queueEvents([{window_alert("'An error occurred. See logs for details.'")}], {constants.CompileVars.SOCKET});
-        }}
-    """
-
-
-  
+ 
     return server_side(
             "_call_script",
             get_fn_signature(call_script),
-            javascript_code=wrapped_code,
+            javascript_code=javascript_code,
             **callback_kwargs,
         )
 
 
-
 def get_event(state, event):
     """Get the event from the given state.
 

From f44c0bc0cb118151e2e0706d688f055c63cff77a Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Fri, 23 Feb 2024 08:44:52 +0100
Subject: [PATCH 09/14] js try/catch & queueEvents added

---
 reflex/event.py | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/reflex/event.py b/reflex/event.py
index 3d98f5ee03..5434b3c500 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -666,15 +666,25 @@ def call_script(
         callback_kwargs = {
             "callback": f"({arg_name}) => queueEvents([{format.format_event(event_spec)}], {constants.CompileVars.SOCKET})"
         }
- 
+    error_event_spec= None
+    wrapped_code = f"""
+    try {{
+        {javascript_code}
+    }} catch (error) {{
+        console.log(error)
+        queueEvents([{format.format_event(error_event_spec)}], {constants.CompileVars.SOCKET})
+    }}
+"""
+
     return server_side(
             "_call_script",
             get_fn_signature(call_script),
-            javascript_code=javascript_code,
+            javascript_code=wrapped_code,
             **callback_kwargs,
         )
 
 
+
 def get_event(state, event):
     """Get the event from the given state.
 

From 9ae325c37661eefec6d3c1718ed0eae3d05b038b Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Sun, 25 Feb 2024 16:13:06 +0100
Subject: [PATCH 10/14] error event created

---
 reflex/__init__.py |  1 +
 reflex/event.py    | 25 ++++++++++++++++++-------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/reflex/__init__.py b/reflex/__init__.py
index 276c05b993..2ee87352fb 100644
--- a/reflex/__init__.py
+++ b/reflex/__init__.py
@@ -132,6 +132,7 @@
         "EventChain",
         "background",
         "call_script",
+        "client_error",
         "clear_local_storage",
         "console_log",
         "download",
diff --git a/reflex/event.py b/reflex/event.py
index 5434b3c500..2d03558fb7 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -18,7 +18,7 @@
 
 from reflex import constants
 from reflex.base import Base
-from reflex.utils import console, format
+from reflex.utils import console, format, prerequisites
 from reflex.utils.types import ArgsSpec
 from reflex.vars import BaseVar, Var
 
@@ -654,6 +654,7 @@ def call_script(
     Raises:
         ValueError: If the callback is not a valid event handler.
     """
+    wrapped_code = None
     callback_kwargs = {}
     if callback is not None:
         arg_name = parse_args_spec(_callback_arg_spec)[0]._var_name
@@ -666,16 +667,16 @@ def call_script(
         callback_kwargs = {
             "callback": f"({arg_name}) => queueEvents([{format.format_event(event_spec)}], {constants.CompileVars.SOCKET})"
         }
-    error_event_spec= None
+    
+    error_event_spec = client_error('client error')
+
     wrapped_code = f"""
     try {{
         {javascript_code}
-    }} catch (error) {{
-        console.log(error)
-        queueEvents([{format.format_event(error_event_spec)}], {constants.CompileVars.SOCKET})
+    }} catch (e) {{
+        queueEvents([{format.format_event(error_event_spec)}], {constants.CompileVars.SOCKET})       
     }}
-"""
-
+    """
     return server_side(
             "_call_script",
             get_fn_signature(call_script),
@@ -683,7 +684,17 @@ def call_script(
             **callback_kwargs,
         )
 
+def client_error(error: Any) -> EventSpec:
+    return server_side(
+        "_client_error",
+        get_fn_signature(client_error),
+        error = error
+    )
 
+def client_error_handler(): # just for test
+    app = getattr(prerequisites.get_app(), constants.CompileVars.APP) 
+    exception_handler = app.exception_handler    
+    return exception_handler
 
 def get_event(state, event):
     """Get the event from the given state.

From c7ee5d16e0aebbfdd0540cc2c5b03ee38f1ce78a Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Sun, 25 Feb 2024 16:13:48 +0100
Subject: [PATCH 11/14] on_error added to add_page to pass custom exception
 handler

---
 reflex/app.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/reflex/app.py b/reflex/app.py
index 7dcca21f01..e665f7a295 100644
--- a/reflex/app.py
+++ b/reflex/app.py
@@ -144,6 +144,9 @@ class App(Base):
     # Custom exception handler
     exception_handler: Optional[Callable] = None
 
+    # client-side exception handler on error
+    load_error_handler: Optional[Callable] = None
+
     def __init__(self, *args, **kwargs):
         """Initialize the app.
 
@@ -394,6 +397,10 @@ def add_page(
         | None = None,
         meta: list[dict[str, str]] = constants.DefaultPage.META_LIST,
         script_tags: list[Component] | None = None,
+        on_error: EventHandler
+        | EventSpec
+        | list[EventHandler | EventSpec]
+        | None = None,
     ):
         """Add a page to the app.
 
@@ -467,6 +474,11 @@ def add_page(
             if not isinstance(on_load, list):
                 on_load = [on_load]
             self.load_events[route] = on_load
+        
+        if on_error:
+            self.load_error_handler = on_error
+
+        
 
     def get_load_events(self, route: str) -> list[EventHandler | EventSpec]:
         """Get the load events for a route.

From 98762071f6c1a6020599bb4f826c1ecf20ddcc39 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Sun, 25 Feb 2024 16:23:41 +0100
Subject: [PATCH 12/14] removed line

---
 reflex/event.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/reflex/event.py b/reflex/event.py
index 2d03558fb7..2e96843747 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -654,7 +654,6 @@ def call_script(
     Raises:
         ValueError: If the callback is not a valid event handler.
     """
-    wrapped_code = None
     callback_kwargs = {}
     if callback is not None:
         arg_name = parse_args_spec(_callback_arg_spec)[0]._var_name

From 1e0948f2511284734372f36ac7b2a95914e82e86 Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Sun, 25 Feb 2024 16:59:52 +0100
Subject: [PATCH 13/14] fixed error handler

---
 reflex/event.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/reflex/event.py b/reflex/event.py
index 2e96843747..c634915f59 100644
--- a/reflex/event.py
+++ b/reflex/event.py
@@ -692,7 +692,7 @@ def client_error(error: Any) -> EventSpec:
 
 def client_error_handler(): # just for test
     app = getattr(prerequisites.get_app(), constants.CompileVars.APP) 
-    exception_handler = app.exception_handler    
+    exception_handler = app.load_error_handler  
     return exception_handler
 
 def get_event(state, event):

From b418b2105cc9f9daa02dc20452f5588eece7358f Mon Sep 17 00:00:00 2001
From: Tanvir Riyad <113178352+tanvirriyad@users.noreply.github.com>
Date: Tue, 5 Mar 2024 10:21:33 +0100
Subject: [PATCH 14/14] test added for custom exception handler

---
 tests/states/__init__.py |  3 +++
 tests/test_app.py        | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/tests/states/__init__.py b/tests/states/__init__.py
index 11e891ab4e..7058760a27 100644
--- a/tests/states/__init__.py
+++ b/tests/states/__init__.py
@@ -28,6 +28,9 @@ def go(self, c: int):
         Yields:
             After each increment.
         """
+        if c < 0:
+            raise ValueError("Test exception")
+        
         for _ in range(c):
             self.value += 1
             yield
diff --git a/tests/test_app.py b/tests/test_app.py
index 08b24b2ea6..4e6a2d99ae 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -1131,6 +1131,24 @@ async def test_process_events(mocker, token: str):
         await app.state_manager.close()
 
 
+@pytest.mark.asyncio
+async def test_custom_exception_handler():
+
+    def custom_exception_handler(exception):
+        print(f"custom exception handler called: {exception}")
+
+    app = App(state=GenState, exception_handler=custom_exception_handler)
+    event = Event(
+        token="t",
+        name="gen_state.go",
+        payload={"c": -1},
+    )
+
+    with pytest.raises(ValueError, match="Test exception"):
+        async for _update in app.process(event, "mock_sid", {}, "127.0.0.1"):
+            pass
+
+
 @pytest.mark.parametrize(
     ("state", "overlay_component", "exp_page_child"),
     [