Better error messages (#2543)

* events fix

* changelog, format, better error msg

* changelog

* changelog

* mix errors

* formatting

* switched from error to warnings

* typo

CHANGELOG.md

@@ -77,6 +77,9 @@ No changes to highlight.
 * Gradio now supports batched functions by [@abidlabs](https://github.com/abidlabs) in [PR 2218](https://github.com/gradio-app/gradio/pull/2218)
 * Add `upload` event for `Video`, `Audio`, `Image`, and `File` components [@dawoodkhan82](https://github.com/dawoodkhan82) in [PR 2448](https://github.com/gradio-app/gradio/pull/2456)
 * Changes websocket path for Spaces as it is no longer necessary to have a different URL for websocket connections on Spaces by [@abidlabs](https://github.com/abidlabs) in [PR 2528](https://github.com/gradio-app/gradio/pull/2528)
+* Clearer error message when events are defined outside of a Blocks scope, and a warning if you
+try to use `Series` or `Parallel` with `Blocks` by [@abidlabs](https://github.com/abidlabs) in [PR 2543](https://github.com/gradio-app/gradio/pull/2543)
+
 
 ## Contributors Shoutout:
 No changes to highlight.

gradio/blocks.py

@@ -10,6 +10,7 @@ import sys
 import time
 import warnings
 import webbrowser
+from tkinter import N
 from types import ModuleType
 from typing import (
     TYPE_CHECKING,
@@ -162,6 +163,10 @@ class Block:
             inputs = [inputs]
         if not isinstance(outputs, list):
             outputs = [outputs]
+        if Context.root_block is None:
+            raise AttributeError(
+                f"{event_name}() and other events can only be called within a Blocks context."
+            )
         Context.root_block.fns.append(BlockFunction(fn, preprocess, postprocess))
         if api_name is not None:
             api_name_ = utils.append_unique_suffix(

gradio/mix.py

@@ -2,6 +2,7 @@
 Ways to transform interfaces to produce new interfaces
 """
 import asyncio
+import warnings
 from typing import TYPE_CHECKING, List
 
 import gradio
@@ -34,6 +35,11 @@ class Parallel(gradio.Interface):
         outputs: List[IOComponent] = []
 
         for interface in interfaces:
+            if not (isinstance(interface, gradio.Interface)):
+                warnings.warn(
+                    "Parallel requires all inputs to be of type Interface. "
+                    "May not work as expected."
+                )
             outputs.extend(interface.output_components)
 
         async def parallel_fn(*args):
@@ -108,6 +114,12 @@ class Series(gradio.Interface):
                 return data[0]
             return data
 
+        for interface in interfaces:
+            if not (isinstance(interface, gradio.Interface)):
+                warnings.warn(
+                    "Series requires all inputs to be of type Interface. May "
+                    "not work as expected."
+                )
         connected_fn.__name__ = " => ".join([io.__name__ for io in interfaces])
 
         kwargs = {

test/test_events.py

@@ -0,0 +1,16 @@
+import pytest
+
+import gradio as gr
+
+
+class TestEventErrors:
+    def test_event_defined_invalid_scope(self):
+        with gr.Blocks() as demo:
+            textbox = gr.Textbox()
+            textbox.blur(lambda x: x + x, textbox, textbox)
+
+        with pytest.raises(AttributeError):
+            demo.load(lambda: "hello", None, textbox)
+
+        with pytest.raises(AttributeError):
+            textbox.change(lambda x: x + x, textbox, textbox)