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rewrite external debuggers section

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David Lord 2020-07-28 07:59:19 -07:00
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docs/errorhandling.rst
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@ -1,8 +1,6 @@
Handling Application Errors
===========================
.. versionadded:: 0.3
Applications fail, servers fail. Sooner or later you will see an exception
in production. Even if your code is 100% correct, you will still see
exceptions from time to time. Why? Because everything else involved will
@ -574,36 +572,34 @@ production with `debug=True`.
Working with Debuggers
----------------------
To dig deeper, possibly to trace code execution, Flask provides a debugger out
of the box (see :ref:`debug-mode`). If you would like to use another Python
debugger, note that debuggers interfere with each other. You have to set some
options in order to use your favorite debugger:
The built-in development server provides a :ref:`debug-mode` that shows
an interactive traceback in the browser when an unhandled error occurs
during a request.
* ``debug`` - whether to enable debug mode and catch exceptions
* ``use_debugger`` - whether to use the internal Flask debugger
* ``use_reloader`` - whether to reload and fork the process if modules
were changed
External debuggers, such as those provided by IDEs, can offer a much
more powerful and visual debugging experience. They can also be used to
step through code during a request before an error is raised, or if no
error is raised.
``debug`` must be True (i.e., exceptions must be caught) in order for the other
two options to have any value.
When using an external debugger, the app should still be in debug mode,
but it can be useful to disable the built-in debugger and reloader,
which can interfere.
If you're using Aptana/Eclipse for debugging you'll need to set both
``use_debugger`` and ``use_reloader`` to False.
When running from the command line:
A possible useful pattern for configuration is to set the following in your
config.yaml (change the block as appropriate for your application, of course)::
.. code-block:: text
FLASK:
DEBUG: True
DEBUG_WITH_APTANA: True
$ export FLASK_ENV=development
$ flask run --no-debugger --no-reload
Then in your application's entry-point (main.py),
you could have something like::
When running from Python:
if __name__ == "__main__":
# To allow aptana to receive errors, set use_debugger=False
app = create_app(config="config.yaml")
.. code-block:: python
use_debugger = app.debug and not(app.config.get('DEBUG_WITH_APTANA'))
app.run(use_debugger=use_debugger, debug=app.debug,
use_reloader=use_debugger, host='0.0.0.0')
app.run(debug=True, use_debugger=False, use_reloader=False)
Disabling these isn't required, an external debugger will continue to
work with the following caveats. If the built-in debugger is not
disabled, it will catch unhandled exceptions before the external
debugger can. If the reloader is not disabled, it could cause an
unexpected reload if code changes during debugging.