From bf27f321a876d37a4da3aea685005059bc87444b Mon Sep 17 00:00:00 2001
From: Thomas Kluyver <thomas@kluyver.me.uk>
Date: Fri, 10 Nov 2017 14:02:55 +0000
Subject: [PATCH] Add Sphinx extension and autogen function for documenting
 config options

---
 traitlets/config/sphinxdoc.py | 159 ++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 traitlets/config/sphinxdoc.py

diff --git a/traitlets/config/sphinxdoc.py b/traitlets/config/sphinxdoc.py
new file mode 100644
index 00000000..8b0bfe76
--- /dev/null
+++ b/traitlets/config/sphinxdoc.py
@@ -0,0 +1,159 @@
+"""Machinery for documenting traitlets config options with Sphinx.
+
+This includes:
+
+- A Sphinx extension defining directives and roles for config options.
+- A function to generate an rst file given an Application instance.
+
+To make this documentation, first set this module as an extension in Sphinx's
+conf.py::
+
+    extensions = [
+        # ...
+        'traitlets.config.sphinxdoc',
+    ]
+
+Autogenerate the config documentation by running code like this before
+Sphinx builds::
+
+    from traitlets.config.sphinxdoc import write_doc
+    from myapp import MyApplication
+
+    writedoc('config/options.rst',    # File to write
+             'MyApp config options',  # Title
+             MyApplication()
+            )
+
+The generated rST syntax looks like this::
+
+    .. configtrait:: Application.log_datefmt
+
+        Description goes here.
+
+    Cross reference like this: :configtrait:`Application.log_datefmt`.
+"""
+from traitlets import Undefined
+from collections import defaultdict
+
+from ipython_genutils.text import indent, dedent
+
+def setup(app):
+    """Registers the Sphinx extension.
+
+    You shouldn't need to call this directly; configure Sphinx to use this
+    module instead.
+    """
+    app.add_object_type('configtrait', 'configtrait', objname='Config option')
+    metadata = {'parallel_read_safe': True, 'parallel_write_safe': True}
+    return metadata
+
+def interesting_default_value(dv):
+    if (dv is None) or (dv is Undefined):
+        return False
+    if isinstance(dv, (str, list, tuple, dict, set)):
+        return bool(dv)
+    return True
+
+def format_aliases(aliases):
+    fmted = []
+    for a in aliases:
+        dashes = '-' if len(a) == 1 else '--'
+        fmted.append('``%s%s``' % (dashes, a))
+    return ', '.join(fmted)
+
+def class_config_rst_doc(cls, trait_aliases):
+    """Generate rST documentation for this class' config options.
+
+    Excludes traits defined on parent classes.
+    """
+    lines = []
+    classname = cls.__name__
+    for k, trait in sorted(cls.class_traits(config=True).items()):
+        ttype = trait.__class__.__name__
+
+        fullname = classname + '.' + trait.name
+        lines += ['.. configtrait:: ' + fullname,
+                  ''
+                 ]
+
+        help = trait.help.rstrip() or 'No description'
+        lines.append(indent(dedent(help), 4) + '\n')
+
+        # Choices or type
+        if 'Enum' in ttype:
+            # include Enum choices
+            lines.append(indent(
+                ':options: ' + ', '.join('``%r``' % x for x in trait.values), 4))
+        else:
+            lines.append(indent(':trait type: ' + ttype, 4))
+
+        # Default value
+        # Ignore boring default values like None, [] or ''
+        if interesting_default_value(trait.default_value):
+            try:
+                dvr = trait.default_value_repr()
+            except Exception:
+                dvr = None  # ignore defaults we can't construct
+            if dvr is not None:
+                if len(dvr) > 64:
+                    dvr = dvr[:61] + '...'
+                # Double up backslashes, so they get to the rendered docs
+                dvr = dvr.replace('\\n', '\\\\n')
+                lines.append(indent(':default: ``%s``' % dvr, 4))
+
+        # Command line aliases
+        if trait_aliases[fullname]:
+            fmt_aliases = format_aliases(trait_aliases[fullname])
+            lines.append(indent(':CLI option: ' + fmt_aliases, 4))
+
+        # Blank line
+        lines.append('')
+
+    return '\n'.join(lines)
+
+def reverse_aliases(app):
+    """Produce a mapping of trait names to lists of command line aliases.
+    """
+    res = defaultdict(list)
+    for alias, trait in app.aliases.items():
+        res[trait].append(alias)
+
+    # Flags also often act as aliases for a boolean trait.
+    # Treat flags which set one trait to True as aliases.
+    for flag, (cfg, _) in app.flags.items():
+        if len(cfg) == 1:
+            classname = list(cfg)[0]
+            cls_cfg = cfg[classname]
+            if len(cls_cfg) == 1:
+                traitname = list(cls_cfg)[0]
+                if cls_cfg[traitname] is True:
+                    res[classname+'.'+traitname].append(flag)
+
+    return res
+
+def write_doc(path, title, app, preamble=None):
+    """Write a rst file documenting config options for a traitlets application.
+
+    Parameters
+    ----------
+
+    path : str
+        The file to be written
+    title : str
+        The human-readable title of the document
+    app : traitlets.config.Application
+        An instance of the application class to be documented
+    preamble : str
+        Extra text to add just after the title (optional)
+    """
+    trait_aliases = reverse_aliases(app)
+    with open(path, 'w') as f:
+        f.write(title + '\n')
+        f.write(('=' * len(title)) + '\n')
+        f.write('\n')
+        if preamble is not None:
+            f.write(preamble + '\n\n')
+
+        for c in app._classes_inc_parents():
+            f.write(class_config_rst_doc(c, trait_aliases))
+            f.write('\n')