matplotlib · QuLogic · Mar 15, 2022 · Jan 8, 2022 · Jan 8, 2022
diff --git a/doc/api/next_api_changes/deprecations/22148-OG.rst b/doc/api/next_api_changes/deprecations/22148-OG.rst
@@ -0,0 +1,5 @@
+Module ``docstring`` deprecated
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The module ``matplotlib.docstring`` is considered internal and public access
+is deprecated.
diff --git a/doc/api/prev_api_changes/api_changes_3.5.0/removals.rst b/doc/api/prev_api_changes/api_changes_3.5.0/removals.rst
@@ -214,7 +214,7 @@ The following class methods have been removed:
 - ``Colorbar.on_mappable_changed`` and ``Colorbar.update_bruteforce``; use
   ``Colorbar.update_normal()`` instead
 - ``docstring.Substitution.from_params`` has been removed; directly assign to
-  ``params`` of `.Substitution` instead
+  ``params`` of ``docstring.Substitution`` instead
 - ``DraggableBase.artist_picker``; set the artist's picker instead
 - ``DraggableBase.on_motion_blit``; use `.DraggableBase.on_motion` instead
 - ``FigureCanvasGTK3._renderer_init``

diff --git a/doc/devel/documenting_mpl.rst b/doc/devel/documenting_mpl.rst
@@ -684,14 +684,14 @@ are:
 2. as automated as possible so that as properties change, the docs
    are updated automatically.
 
-The ``@docstring.interpd`` decorator implements this.  Any function accepting
+The ``@_docstring.interpd`` decorator implements this.  Any function accepting
 `.Line2D` pass-through ``kwargs``, e.g., `matplotlib.axes.Axes.plot`, can list
 a summary of the `.Line2D` properties, as follows:
 
 .. code-block:: python
 
   # in axes.py
-  @docstring.interpd
+  @_docstring.interpd
   def plot(self, *args, **kwargs):
       """
       Some stuff omitted
@@ -726,7 +726,7 @@ gets interpolated into the docstring.
 
 Note that this scheme does not work for decorating an Artist's ``__init__``, as
 the subclass and its properties are not defined yet at that point.  Instead,
-``@docstring.interpd`` can be used to decorate the class itself -- at that
+``@_docstring.interpd`` can be used to decorate the class itself -- at that
 point, `.kwdoc` can list the properties and interpolate them into
 ``__init__.__doc__``.
 

diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -106,7 +106,7 @@
 
 # cbook must import matplotlib only within function
 # definitions, so it is safe to import from it here.
-from . import _api, _version, cbook, docstring, rcsetup
+from . import _api, _version, cbook, _docstring, rcsetup
 from matplotlib.cbook import sanitize_sequence
 from matplotlib._api import MatplotlibDeprecationWarning
 from matplotlib.rcsetup import validate_backend, cycler
@@ -593,7 +593,7 @@ def gen_candidates():
 _deprecated_remain_as_none = {}
 
 
-@docstring.Substitution(
+@_docstring.Substitution(
     "\n".join(map("- {}".format, sorted(rcsetup._validators, key=str.lower)))
 )
 class RcParams(MutableMapping, dict):

diff --git a/lib/matplotlib/_docstring.py b/lib/matplotlib/_docstring.py
@@ -0,0 +1,97 @@
+import inspect
+
+from . import _api
+
+
+class Substitution:
+    """
+    A decorator that performs %-substitution on an object's docstring.
+
+    This decorator should be robust even if ``obj.__doc__`` is None (for
+    example, if -OO was passed to the interpreter).
+
+    Usage: construct a docstring.Substitution with a sequence or dictionary
+    suitable for performing substitution; then decorate a suitable function
+    with the constructed object, e.g.::
+
+        sub_author_name = Substitution(author='Jason')
+
+        @sub_author_name
+        def some_function(x):
+            "%(author)s wrote this function"
+
+        # note that some_function.__doc__ is now "Jason wrote this function"
+
+    One can also use positional arguments::
+
+        sub_first_last_names = Substitution('Edgar Allen', 'Poe')
+
+        @sub_first_last_names
+        def some_function(x):
+            "%s %s wrote the Raven"
+    """
+    def __init__(self, *args, **kwargs):
+        if args and kwargs:
+            raise TypeError("Only positional or keyword args are allowed")
+        self.params = params = args or kwargs
+
+    def __call__(self, func):
+        if func.__doc__:
+            func.__doc__ = inspect.cleandoc(func.__doc__) % self.params
+        return func
+
+    def update(self, *args, **kwargs):
+        """
+        Update ``self.params`` (which must be a dict) with the supplied args.
+        """
+        self.params.update(*args, **kwargs)
+
+
+class _ArtistKwdocLoader(dict):
+    def __missing__(self, key):
+        if not key.endswith(":kwdoc"):
+            raise KeyError(key)
+        name = key[:-len(":kwdoc")]
+        from matplotlib.artist import Artist, kwdoc
+        try:
+            cls, = [cls for cls in _api.recursive_subclasses(Artist)
+                    if cls.__name__ == name]
+        except ValueError as e:
+            raise KeyError(key) from e
+        return self.setdefault(key, kwdoc(cls))
+
+
+class _ArtistPropertiesSubstitution(Substitution):
+    """
+    A `.Substitution` with two additional features:
+
+    - Substitutions of the form ``%(classname:kwdoc)s`` (ending with the
+      literal ":kwdoc" suffix) trigger lookup of an Artist subclass with the
+      given *classname*, and are substituted with the `.kwdoc` of that class.
+    - Decorating a class triggers substitution both on the class docstring and
+      on the class' ``__init__`` docstring (which is a commonly required
+      pattern for Artist subclasses).
+    """
+
+    def __init__(self):
+        self.params = _ArtistKwdocLoader()
+
+    def __call__(self, obj):
+        super().__call__(obj)
+        if isinstance(obj, type) and obj.__init__ != object.__init__:
+            self(obj.__init__)
+        return obj
+
+
+def copy(source):
+    """Copy a docstring from another source function (if present)."""
+    def do_copy(target):
+        if source.__doc__:
+            target.__doc__ = source.__doc__
+        return target
+    return do_copy
+
+
+# Create a decorator that will house the various docstring snippets reused
+# throughout Matplotlib.
+dedent_interpd = interpd = _ArtistPropertiesSubstitution()
diff --git a/lib/matplotlib/_enums.py b/lib/matplotlib/_enums.py
@@ -11,7 +11,7 @@
 """
 
 from enum import Enum, auto
-from matplotlib import docstring
+from matplotlib import _docstring
 
 
 class _AutoStringNameEnum(Enum):
@@ -181,5 +181,5 @@ def demo():
         + ", ".join([f"'{cs.name}'" for cs in CapStyle]) \
         + "}"
 
-docstring.interpd.update({'JoinStyle': JoinStyle.input_description,
+_docstring.interpd.update({'JoinStyle': JoinStyle.input_description,
                           'CapStyle': CapStyle.input_description})