| ============================== |
| MEP10: Docstring consistency |
| ============================== |
| .. contents:: |
| :local: |
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| Status |
| ====== |
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|
| **Progress** |
|
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| This is still an on-going effort |
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|
| Branches and Pull requests |
| ========================== |
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| Abstract |
| ======== |
|
|
| matplotlib has a great deal of inconsistency between docstrings. This |
| not only makes the docs harder to read, but it is harder on |
| contributors, because they don't know which specifications to follow. |
| There should be a clear docstring convention that is followed |
| consistently. |
|
|
| The organization of the API documentation is difficult to follow. |
| Some pages, such as pyplot and axes, are enormous and hard to browse. |
| There should instead be short summary tables that link to detailed |
| documentation. In addition, some of the docstrings themselves are |
| quite long and contain redundant information. |
|
|
| Building the documentation takes a long time and uses a :file:`make.py` |
| script rather than a Makefile. |
|
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| Detailed description |
| ==================== |
|
|
| There are number of new tools and conventions available since |
| matplotlib started using Sphinx that make life easier. The following |
| is a list of proposed changes to docstrings, most of which involve |
| these new features. |
|
|
| Numpy docstring format |
| ---------------------- |
|
|
| `Numpy docstring format |
| <https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt>`_: |
| This format divides the docstring into clear sections, each having |
| different parsing rules that make the docstring easy to read both as |
| raw text and as HTML. We could consider alternatives, or invent our |
| own, but this is a strong choice, as it's well used and understood in |
| the Numpy/Scipy community. |
|
|
| Cross references |
| ---------------- |
|
|
| Most of the docstrings in matplotlib use explicit "roles" when linking |
| to other items, for example: ``:func:`myfunction```. As of Sphinx |
| 0.4, there is a "default_role" that can be set to "obj", which will |
| polymorphically link to a Python object of any type. This allows one |
| to write ```myfunction``` instead. This makes docstrings much easier |
| to read and edit as raw text. Additionally, Sphinx allows for setting |
| a current module, so links like ```~matplotlib.axes.Axes.set_xlim``` |
| could be written as ```~axes.Axes.set_xlim```. |
| |
| Overriding signatures |
| --------------------- |
|
|
| Many methods in matplotlib use the ``*args`` and ``**kwargs`` syntax |
| to dynamically handle the keyword arguments that are accepted by the |
| function, or to delegate on to another function. This, however, is |
| often not useful as a signature in the documentation. For this |
| reason, many matplotlib methods include something like:: |
| |
| def annotate(self, *args, **kwargs): |
| """ |
| Create an annotation: a piece of text referring to a data |
| point. |
|
|
| Call signature:: |
| |
| annotate(s, xy, xytext=None, xycoords='data', |
| textcoords='data', arrowprops=None, **kwargs) |
| """ |
|
|
| This can't be parsed by Sphinx, and is rather verbose in raw text. As |
| of Sphinx 1.1, if the ``autodoc_docstring_signature`` config value is |
| set to True, Sphinx will extract a replacement signature from the |
| first line of the docstring, allowing this:: |
| |
| def annotate(self, *args, **kwargs): |
| """ |
| annotate(s, xy, xytext=None, xycoords='data', |
| textcoords='data', arrowprops=None, **kwargs) |
|
|
| Create an annotation: a piece of text referring to a data |
| point. |
| """ |
|
|
| The explicit signature will replace the actual Python one in the |
| generated documentation. |
|
|
| Linking rather than duplicating |
| ------------------------------- |
|
|
| Many of the docstrings include long lists of accepted keywords by |
| interpolating things into the docstring at load time. This makes the |
| docstrings very long. Also, since these tables are the same across |
| many docstrings, it inserts a lot of redundant information in the docs |
| -- particularly a problem in the printed version. |
|
|
| These tables should be moved to docstrings on functions whose only |
| purpose is for help. The docstrings that refer to these tables should |
| link to them, rather than including them verbatim. |
|
|
| autosummary extension |
| --------------------- |
|
|
| The Sphinx autosummary extension should be used to generate summary |
| tables, that link to separate pages of documentation. Some classes |
| that have many methods (e.g. `~.axes.Axes`) should be documented with |
| one method per page, whereas smaller classes should have all of their |
| methods together. |
|
|
| Examples linking to relevant documentation |
| ------------------------------------------ |
|
|
| The examples, while helpful at illustrating how to use a feature, do |
| not link back to the relevant docstrings. This could be addressed by |
| adding module-level docstrings to the examples, and then including |
| that docstring in the parsed content on the example page. These |
| docstrings could easily include references to any other part of the |
| documentation. |
|
|
| Documentation using help() vs. a browser |
| ---------------------------------------- |
|
|
| Using Sphinx markup in the source allows for good-looking docs in your |
| browser, but the markup also makes the raw text returned using help() |
| look terrible. One of the aims of improving the docstrings should be |
| to make both methods of accessing the docs look good. |
|
|
| Implementation |
| ============== |
|
|
| 1. The numpydoc extensions should be turned on for matplotlib. There |
| is an important question as to whether these should be included in |
| the matplotlib source tree, or used as a dependency. Installing |
| Numpy is not sufficient to get the numpydoc extensions -- it's a |
| separate install procedure. In any case, to the extent that they |
| require customization for our needs, we should endeavor to submit |
| those changes upstream and not fork them. |
|
|
| 2. Manually go through all of the docstrings and update them to the |
| new format and conventions. Updating the cross references (from |
| ```:func:`myfunc``` to ```func```) may be able to be |
| semi-automated. This is a lot of busy work, and perhaps this labor |
| should be divided on a per-module basis so no single developer is |
| over-burdened by it. |
|
|
| 3. Reorganize the API docs using autosummary and ``sphinx-autogen``. |
| This should hopefully have minimal impact on the narrative |
| documentation. |
|
|
| 4. Modify the example page generator (:file:`gen_rst.py`) so that it |
| extracts the module docstring from the example and includes it in a |
| non-literal part of the example page. |
|
|
| 5. Use ``sphinx-quickstart`` to generate a new-style Sphinx Makefile. |
| The following features in the current :file:`make.py` will have to be |
| addressed in some other way: |
|
|
| - Copying of some static content |
|
|
| - Specifying a "small" build (only low-resolution PNG files for examples) |
|
|
| Steps 1, 2, and 3 are interdependent. 4 and 5 may be done |
| independently, though 5 has some dependency on 3. |
|
|
| Backward compatibility |
| ====================== |
|
|
| As this mainly involves docstrings, there should be minimal impact on |
| backward compatibility. |
|
|
| Alternatives |
| ============ |
|
|
| None yet discussed. |
|
|
