Merge pull request #860 from plotly/843-simple-errors

dev_tools_prune_errors

Author: byronz

dash/CHANGELOG.md

@@ -1,3 +1,7 @@
+## [UNRELEASED]
+### Added
+- [#860](https://github.com/plotly/dash/pull/860) Adds a new arg `dev_tools_prune_errors` to `app.run_server` and `app.enable_dev_tools`. Default `True`, tracebacks only include user code and below. Set it to `False` for the previous behavior showing all the Dash and Flask parts of the stack.
+
 ## [1.1.1] - 2019-08-06
 ### Changed
 - Bumped dash-core-components version from 1.1.0 to [1.1.1](https://github.com/plotly/dash-core-components/blob/master/CHANGELOG.md#111---2019-08-06)

dash/dash.py

@@ -19,6 +19,7 @@
 import flask
 from flask import Flask, Response
 from flask_compress import Compress
+from werkzeug.debug.tbtools import get_current_traceback
 
 import plotly
 import dash_renderer
@@ -1168,7 +1169,8 @@ def callback(self, output, inputs=[], state=[]):
         def wrap_func(func):
             @wraps(func)
             def add_context(*args, **kwargs):
-                output_value = func(*args, **kwargs)
+                # don't touch the comment on the next line - used by debugger
+                output_value = func(*args, **kwargs)  # %% callback invoked %%
                 if multi:
                     if not isinstance(output_value, (list, tuple)):
                         raise exceptions.InvalidCallbackReturnValue(
@@ -1390,7 +1392,8 @@ def _setup_dev_tools(self, **kwargs):
                 'props_check',
                 'serve_dev_bundles',
                 'hot_reload',
-                'silence_routes_logging'
+                'silence_routes_logging',
+                'prune_errors'
         ):
             dev_tools[attr] = get_combined_config(
                 attr, kwargs.get(attr, None), default=debug
@@ -1419,7 +1422,8 @@ def enable_dev_tools(
             dev_tools_hot_reload_interval=None,
             dev_tools_hot_reload_watch_interval=None,
             dev_tools_hot_reload_max_retry=None,
-            dev_tools_silence_routes_logging=None):
+            dev_tools_silence_routes_logging=None,
+            dev_tools_prune_errors=None):
         """
         Activate the dev tools, called by `run_server`. If your application is
         served by wsgi and you want to activate the dev tools, you can call
@@ -1483,6 +1487,11 @@ def enable_dev_tools(
             env: ``DASH_SILENCE_ROUTES_LOGGING``
         :type dev_tools_silence_routes_logging: bool
 
+        :param dev_tools_prune_errors: Reduce tracebacks to just user code,
+            stripping out Flask and Dash pieces. `True` by default, set to
+            `False` to see the complete traceback.
+        :type dev_tools_prune_errors: bool
+
         :return: debug
         """
         if debug is None:
@@ -1497,7 +1506,8 @@ def enable_dev_tools(
             hot_reload_interval=dev_tools_hot_reload_interval,
             hot_reload_watch_interval=dev_tools_hot_reload_watch_interval,
             hot_reload_max_retry=dev_tools_hot_reload_max_retry,
-            silence_routes_logging=dev_tools_silence_routes_logging
+            silence_routes_logging=dev_tools_silence_routes_logging,
+            prune_errors=dev_tools_prune_errors
         )
 
         if dev_tools.silence_routes_logging:
@@ -1527,6 +1537,21 @@ def enable_dev_tools(
             _reload.watch_thread.daemon = True
             _reload.watch_thread.start()
 
+        if debug and dev_tools.prune_errors:
+            @self.server.errorhandler(Exception)
+            def _wrap_errors(_):
+                # find the callback invocation, if the error is from a callback
+                # and skip the traceback up to that point
+                # if the error didn't come from inside a callback, we won't
+                # skip anything.
+                tb = get_current_traceback()
+                skip = 0
+                for i, line in enumerate(tb.plaintext.splitlines()):
+                    if "%% callback invoked %%" in line:
+                        skip = int((i + 1) / 2)
+                        break
+                return get_current_traceback(skip=skip).render_full(), 500
+
         if (debug and dev_tools.serve_dev_bundles and
                 not self.scripts.config.serve_locally):
             # Dev bundles only works locally.
@@ -1594,6 +1619,7 @@ def run_server(
             dev_tools_hot_reload_watch_interval=None,
             dev_tools_hot_reload_max_retry=None,
             dev_tools_silence_routes_logging=None,
+            dev_tools_prune_errors=None,
             **flask_run_options):
         """
         Start the flask server in local mode, you should not run this on a
@@ -1652,6 +1678,11 @@ def run_server(
             env: ``DASH_SILENCE_ROUTES_LOGGING``
         :type dev_tools_silence_routes_logging: bool
 
+        :param dev_tools_prune_errors: Reduce tracebacks to just user code,
+            stripping out Flask and Dash pieces. Only available with debugging.
+            `True` by default, set to `False` to see the complete traceback.
+        :type dev_tools_prune_errors: bool
+
         :param flask_run_options: Given to `Flask.run`
 
         :return:
@@ -1666,6 +1697,7 @@ def run_server(
             dev_tools_hot_reload_watch_interval,
             dev_tools_hot_reload_max_retry,
             dev_tools_silence_routes_logging,
+            dev_tools_prune_errors
         )
 
         if self._dev_tools.silence_routes_logging:

tests/integration/devtools/test_devtools_error_handling.py

@@ -6,7 +6,7 @@
 from dash.exceptions import PreventUpdate
 
 
-def test_dveh001_python_errors(dash_duo):
+def app_with_errors():
     app = dash.Dash(__name__)
 
     app.layout = html.Div(
@@ -19,10 +19,26 @@ def test_dveh001_python_errors(dash_duo):
     @app.callback(Output("output", "children"), [Input("python", "n_clicks")])
     def update_output(n_clicks):
         if n_clicks == 1:
-            1 / 0
+            return bad_sub()
         elif n_clicks == 2:
             raise Exception("Special 2 clicks exception")
 
+    def bad_sub():
+        return 1 / 0
+
+    return app
+
+
+def get_error_html(dash_duo, index):
+    # error is in an iframe so is annoying to read out - get it from the store
+    return dash_duo.driver.execute_script(
+        "return store.getState().error.backEnd[{}].error.html;".format(index)
+    )
+
+
+def test_dveh001_python_errors(dash_duo):
+    app = app_with_errors()
+
     dash_duo.start_server(
         app,
         debug=True,
@@ -49,6 +65,58 @@ def update_output(n_clicks):
     dash_duo.find_element(".test-devtools-error-toggle").click()
     dash_duo.percy_snapshot("devtools - python exception - 2 errors open")
 
+    # the top (first) error is the most recent one - ie from the second click
+    error0 = get_error_html(dash_duo, 0)
+    # user part of the traceback shown by default
+    assert 'in update_output' in error0
+    assert 'Special 2 clicks exception' in error0
+    assert 'in bad_sub' not in error0
+    # dash and flask part of the traceback not included
+    assert '%% callback invoked %%' not in error0
+    assert 'self.wsgi_app' not in error0
+
+    error1 = get_error_html(dash_duo, 1)
+    assert 'in update_output' in error1
+    assert 'in bad_sub' in error1
+    assert 'ZeroDivisionError' in error1
+    assert '%% callback invoked %%' not in error1
+    assert 'self.wsgi_app' not in error1
+
+
+def test_dveh006_long_python_errors(dash_duo):
+    app = app_with_errors()
+
+    dash_duo.start_server(
+        app,
+        debug=True,
+        use_reloader=False,
+        use_debugger=True,
+        dev_tools_hot_reload=False,
+        dev_tools_prune_errors=False,
+    )
+
+    dash_duo.find_element("#python").click()
+    dash_duo.find_element("#python").click()
+    dash_duo.wait_for_text_to_equal(dash_duo.devtools_error_count_locator, "2")
+
+    dash_duo.find_element(".test-devtools-error-toggle").click()
+
+    error0 = get_error_html(dash_duo, 0)
+    assert 'in update_output' in error0
+    assert 'Special 2 clicks exception' in error0
+    assert 'in bad_sub' not in error0
+    # dash and flask part of the traceback ARE included
+    # since we set dev_tools_prune_errors=False
+    assert '%% callback invoked %%' in error0
+    assert 'self.wsgi_app' in error0
+
+    error1 = get_error_html(dash_duo, 1)
+    assert 'in update_output' in error1
+    assert 'in bad_sub' in error1
+    assert 'ZeroDivisionError' in error1
+    assert '%% callback invoked %%' in error1
+    assert 'self.wsgi_app' in error1
+
 
 def test_dveh002_prevent_update_not_in_error_msg(dash_duo):
     # raising PreventUpdate shouldn't display the error message

tests/integration/devtools/test_props_check.py

@@ -15,22 +15,22 @@
         "fail": True,
         "name": 'missing required "value" inside options',
         "component": dcc.Checklist,
-        "props": {"options": [{"label": "hello"}], "values": ["test"]},
+        "props": {"options": [{"label": "hello"}], "value": ["test"]},
     },
     "invalid-nested-prop": {
         "fail": True,
         "name": "invalid nested prop",
         "component": dcc.Checklist,
         "props": {
             "options": [{"label": "hello", "value": True}],
-            "values": ["test"],
+            "value": ["test"],
         },
     },
     "invalid-arrayOf": {
         "fail": True,
         "name": "invalid arrayOf",
         "component": dcc.Checklist,
-        "props": {"options": "test", "values": []},
+        "props": {"options": "test", "value": []},
     },
     "invalid-oneOf": {
         "fail": True,
@@ -82,7 +82,7 @@
         "component": dcc.Checklist,
         "props": {
             "options": [{"label": "hello", "value": "test"}],
-            "values": "test",
+            "value": "test",
         },
     },
     "no-properties": {