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Former-commit-id:06a8b51d6d[formerly 64fa9254b946eae7e61bbc3f513b7c3696c4f54f] Former-commit-id:9f19e3f712
64 lines
2.4 KiB
ReStructuredText
Executable file
64 lines
2.4 KiB
ReStructuredText
Executable file
======================
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Debugging Applications
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======================
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.. module:: werkzeug
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Depending on the WSGI gateway/server, exceptions are handled differently.
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But most of the time, exceptions go to stderr or the error log.
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Since this is not the best debugging environment, Werkzeug provides a
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WSGI middleware that renders nice debugging tracebacks, optionally with an
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AJAX based debugger (which allows to execute code in the context of the
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traceback's frames).
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The interactive debugger however does not work in forking environments
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which makes it nearly impossible to use on production servers. Also the
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debugger allows the execution of arbitrary code which makes it a major
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security risk and **must never be used on production machines** because of
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that.
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Enabling the Debugger
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=====================
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You can enable the debugger by wrapping the application in a
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:class:`DebuggedApplication` middleware. Additionally there are
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parameters to the :func:`run_simple` function to enable it because this
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is a common task during development.
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.. autoclass:: DebuggedApplication
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Using the Debugger
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==================
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Once enabled and an error happens during a request you will see a detailed
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traceback instead of a general "internal server error". If you have the
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`evalex` feature enabled you can also get a traceback for every frame in
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the traceback by clicking on the console icon.
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Once clicked a console opens where you can execute Python code in:
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.. image:: _static/debug-screenshot.png
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:alt: a screenshot of the interactive debugger
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:align: center
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Inside the interactive consoles you can execute any kind of Python code.
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Unlike regular Python consoles the output of the object reprs is colored
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and stripped to a reasonable size by default. If the output is longer
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than what the console decides to display a small plus sign is added to
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the repr and a click will expand the repr.
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To display all variables that are defined in the current frame you can
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use the `dump()` function. You can call it without arguments to get a
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detailed list of all variables and their values, or with an object as
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argument to get a detailed list of all the attributes it has.
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Pasting Errors
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==============
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If you click on the `Traceback` title the traceback switches over to a text
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based one. The text based one can be pasted to `paste.pocoo.org`_ with one
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click.
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.. _paste.pocoo.org: http://paste.pocoo.org/
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