GSoC 2016 Post-midterm ideas

Roman Valls Guimerà bio photo By Roman Valls Guimerà Comment

GSoC 2016 Post-midterm ideas

After having a successful midterm evaluation for argparse2cwl where Anton Khodak successfully:

  1. Surveyed the python argument parsing landscape.
  2. Covered the argparse API with equivalent CWL terms.
  3. Generated CWL files out of an example bioinformatics package, CNVkit.
  4. Wrote tests and documentation for the above points.
  5. Engaging with the community through gitter, mailing list and his project blog, while getting ideas on how to improve and conduct the project in a way that is helpful to the community.

He will be tackling the next stage of this GSoC 2016 on CWL. This is a summary of the brainstorming and ideas that Anton is going to pick and undertake during the next 6 weeks.


The idea would be to have a commandline tool that:

  1. Queries/downloads an arbitrary pypi package specified by the user (i.e: ./pypi2cwl cnvkit).
  2. Checks for argparse presence in its scripts/code.
  3. Runs argparse2cwl against it and generates the associated CWL output files.
  4. Generates a pull request for review to add the templates to the CWL community repository

Building on top of the CNVkit experience that Anton has, this would be very valuable to automate the wrapping process further and potentially explore the conversion of python packages in bulk.

A desired outcome for this sub-project would be to have an output similar to that of, where the overall coverage and bugs can be spotted quickly.


As any conversion tool that has a “2” in the middle, isn’t it worth to flip it over? That’s what cwl2argparse would do ;)

In a future where everyone wraps their tools with CWL (ha!), one would like to be able to:

  1. Write a cwltool definition.
  2. Run cwl2argparse against you_newly_wrapped_tool.cwl.
  3. Generate argparse code to import into your Python program.

Since we have already generated CNVkit’s CWL, what would be the expected output of, for instance cwl2argpase tools/cnvkit-batch.cwl would generate an argparse definition that could be imported in a Python program and used, i.e:

P_batch = AP_subparsers.add_parser('batch', help=_cmd_batch.__doc__)
P_batch.add_argument('bam_files', nargs='*',
        help="Mapped sequence reads (.bam)")
P_batch.add_argument('-y', '--male-reference', action='store_true',
        help="""Use or assume a male reference (i.e. female samples will have +1
                log-CNR of chrX; otherwise male samples would have -1 chrX).""")
P_batch.add_argument('-c', '--count-reads', action='store_true',
        help="""Get read depths by counting read midpoints within each bin.
                (An alternative algorithm).""")
P_batch.add_argument("--drop-low-coverage", action='store_true',
        help="""Drop very-low-coverage bins before segmentation to avoid
                false-positive deletions in poor-quality tumor samples.""")

Pretty much what John Chilton does for Bash via cwl2script, Anton can try to do it for python’s argparse so that a developer only has to update their tool definition to generate argparse code for newly introduced flags. Adding in new python argparsers such as click, arg[N] or optparse

According to Anton’s first blogpost, there are a few other argument parsers that could use some CWL automation. The next on the list to implement, when accounting for packages that use it, would be python’s core argument array (arg[0], arg[1], …). On the other hand, given its free-form nature, it can be challenging to assign and transform semantics from it to CWL like the others parsers. For instance, flags, arguments and types are all well specified on click or argparse.

Or perhaps click would be more interesting to wrap given its ramping up in usage by the community? Worth exploring in any case.

Discarded idea (for now): Fuzzing support for argparse2cwl: argparse2cwl-fuzz

Last and least, after some deliberation, argparse2cwl-fuzz could be a bit too far away from this project scope and resources: writing a stub for bioinformatics fuzzing.

As pointed out in the original proposal:

(…) explore and optimize the parameter/flag space of i.e, bioinformatic aligners with Teaser.”

Instead of going all the way and create a benchmarking/validation suite and file format fuzzing, just providing some support for argparse2cwl and generating different commandline flag combinations, somewhat like biopsy and Teaser do.

Could be tackled in a future GSoC project maybe?

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