Merge pull request #1288 from dannysepler/same-module

Debug in same module

Author: alexcjohnson

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - [#1249](https://github.com/plotly/dash/pull/1249) Fixes [#919](https://github.com/plotly/dash/issues/919) so `dash.testing` is compatible with more `pytest` plugins, particularly `pytest-flake8` and `pytest-black`.
 - [#1248](https://github.com/plotly/dash/pull/1248) Fixes [#1245](https://github.com/plotly/dash/issues/1245), so you can use prop persistence with components that have dict IDs, ie for pattern-matching callbacks.
 - [#1185](https://github.com/plotly/dash/pull/1185) Sort asset directories, same as we sort files inside those directories. This way if you need your assets loaded in a certain order, you can add prefixes to subdirectory names and enforce that order.
+- [#1288](https://github.com/plotly/dash/pull/1288) Closes [#1285](https://github.com/plotly/dash/issues/1285): Debug=True should work in the __main__ module.
 
 ## [1.12.0] - 2020-05-05
 ### Added

dash/dash.py

@@ -1338,14 +1338,19 @@ def enable_dev_tools(
             _reload = self._hot_reload
             _reload.hash = generate_hash()
 
+            # find_loader should return None on __main__ but doesn't
+            # on some python versions https://bugs.python.org/issue14710
+            packages = [
+                pkgutil.find_loader(x)
+                for x in list(ComponentRegistry.registry) + ["dash_renderer"]
+                if x != "__main__"
+            ]
+
             component_packages_dist = [
                 os.path.dirname(package.path)
                 if hasattr(package, "path")
                 else package.filename
-                for package in (
-                    pkgutil.find_loader(x)
-                    for x in list(ComponentRegistry.registry) + ["dash_renderer"]
-                )
+                for package in packages
             ]
 
             _reload.watch_thread = threading.Thread(