argparse2tool

|PyPI| |Build Status|

This project aims to provide a drop-in replacement for argparse which allows generating Galaxy XML and CWL Tools.

It is quite literally a drop-in replacement. You (or the upstream tool author) can use argparse completely as normal

.. code:: python

import argparse

When this package is installed and PYTHONPATH=$(argparse2tool) is set the dropin replacement of argparse is used ahead of the system argparse, argparse2tool will capture all argparse function calls, and process them specially.

This information captured in this process is used to produce Galaxy Tool XML <https://github.com/hexylena/galaxyxml>__ when it's requested with the --generate_galaxy_xml flag, or CWL Tools <http://www.commonwl.org/v1.0/CommandLineTool.html>__ when requested with the --generate_cwl_tool flag.

For our example python script <./examples/example.py>__ you can see the generated Galaxy XML <./examples/example.xml>__ and CWL Tools <./examples/example.cwl>__.

Running

To generate XML or CWL, run your tool with the appropriate command line flag

.. code:: console

$ PYTHONPATH=$(argparse2tool) <tool command> --generate_galaxy_xml <other options> > tool.xml
$ PYTHONPATH=$(argparse2tool) <tool command> --generate_cwl_tool <other options> > tool.cwl

The project includes a sample example.py file which uses as many argparse features as possible. CWL and Galaxy XML support different portions feature sets which will be visible in the generated outputs.

.. code:: console

$ PYTHONPATH=$(argparse2tool) python example.py --generate_galaxy_xml
$ PYTHONPATH=$(argparse2tool) python example.py --generate_cwl_tool

CWL Specific Functionality

Example for `CNVkit <https://github.com/etal/cnvkit>`__ toolkit

.. code:: console

    $ cnvkit.py batch --generate_cwl_tool -d ~/cnvkit-tools/ --generate_outputs

If there are subcommands in the provided command, all possible tools
will be generated, for instance, for CNVkit

.. code:: console

    $ cnvkit.py --generate_cwl_tool

will produce CWL tool descriptions for ``cnvkit.py batch``,
``cnvkit.py access``, ``cnvkit.py export bed``, ``cnvkit.py export cdt``
and all other subcommands.

Other options (which work only with ``--generate_cwl_tool`` provided,
except for help message) are:

-  ``-o FILENAME``, ``--output_section FILENAME``: File with manually
   filled output section which is put to a formed CWL tool.
   ``argparse2tool`` is not very good at generating outputs, it
   recognizes output files only if they have type
   ``argparse.FileType('w')``, so output section is often blank and
   should be filled manually.

-  ``-go``, ``--generate_outputs``: flag for generating outputs not only
   from arguments that are instances of ``argparse.FileType('w')``, but
   also from every argument which contains ``output`` keyword in its
   name. For instance, argument ``--output-file`` with no type will also
   be placed to output section. However, '--output-directory' argument
   will also be treated like File, so generated tools must be checked
   carefully if when this option is selected.

-  ``-b``, ``basecommand``: command which appears in ``basecommand``
   field in a resulting tool. It is handy to use this option when you
   run tool with shebang, but want ``python`` to be in ``basecommand``
   field and the file amidst arguments. Example:

   ``$ .search.py --generate_cwl_tool -b python``.

Basecommand of the formed tool will be ``['python']``, and ``search``
will be a positional argument on position 0.

-  ``-d``, ``--directory``: directory for storing tool descriptions.

-  ``--help_arg2cwl``: prints this help message.

How it works
------------

Internally, ``argparse2tool``, masquerading as ``argparse`` attempts to
find and import the **real** argparse. It then stores a reference to the
code module for the system argparse, and presents the user with all of
the functions that stdlib's argparse provides. Every function call is
passed through the system argparse. However, argparse2tool captures the
details of those calls and when Tool XML or CWL is requested, it builds
up the tool definition and prints it out to standard output.

Examples
--------

You can see the ``example.py`` file for an example with numerous types
of arguments and options that you might see in real tools. Accordingly
there is an ``example.xml`` file with the output.

It doesn't work!!
-----------------

If you are not able to use the
``--generate_galaxy_xml``/``--generate_cwl_tool`` flags after
installing, it is probably because of module load order.
``argparse2tool`` must precede ``argparse`` in the path.

To easily correct this, run the tool ``argparse2tool`` which
is installed as part of this package. Correctly functioning paths will
produce the following:

.. code:: console

    $ argparse2tool
    PATH_TO_THE_DROPINS

while incorrectly ordered paths will produce a helpful error message:

.. code:: console

    $ argparse2tool
    no dropins dir...

This is intended to be used inline:

.. code:: console

    user@host:$ PYTHONPATH=$(argparse2tool) python my_script.py --generate_galaxy_xml

Limitations
-----------

This code doesn't cover the entirety of the ``argparse`` API yet, and
there are some bugs to work out on the XML generation side:

-  argparse

   -  groups not supported (in galaxy, everything should still work in
      argparse)
   -  some features like templating of the version string (please submit
      bugs)

-  galaxyxml

   -  bugs in conditionals/whens (probably)

-  argparse2tool Galaxy XML Output

   -  support declaring output files in an ``argparse``-esque manner

-  argparse2tool CWL Output

   -  Some of argparse features can not be ported to CWL.

      1. ``nargs=N``. Number of arguments can not be specified in CWL
         (yet).
      2. ``const`` argument of ``add_argument()``. All constants must be
         specified in job files.
      3. Custom types and custom actions are not supported.
      4. Argument groups don't work in CWL as arguments are sorted with
         a `special
         algorithm <http://www.commonwl.org/draft-3/CommandLineTool.html#Input_binding>`__
      5. Mutual exclusion is not supported.

License
-------

Apache License, v2

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