Make FromConfigMixin public and include in documentation (#884)

Author: mauvilsa

CHANGELOG.rst

@@ -25,6 +25,8 @@ Added
   (`#875 <https://github.com/omni-us/jsonargparse/pull/875>`__).
 - ``add_class_arguments`` skip support for callable return class parameters
   (`#882 <https://github.com/omni-us/jsonargparse/pull/882>`__).
+- ``FromConfigMixin`` is now an official public API feature
+  (`#884 <https://github.com/omni-us/jsonargparse/pull/884>`__).
 
 Fixed
 ^^^^^

DOCUMENTATION.rst

@@ -1465,6 +1465,28 @@ methods are:
     is possible to use classes from third party libraries which is not possible
     for developers to modify.
 
+From config mixin
+-----------------
+
+For classes that should support direct instantiation from configuration values,
+:class:`.FromConfigMixin` adds a ``from_config`` class method. It can be useful
+for small utilities that need to load constructor values from a dictionary or a
+configuration file in one call.
+
+.. doctest::
+
+    >>> from jsonargparse import FromConfigMixin
+    >>> class Client(FromConfigMixin):
+    ...     def __init__(self, host: str = "localhost", port: int = 80):
+    ...         self.host = host
+    ...         self.port = port
+    >>> client = Client.from_config({"host": "api.local", "port": 8080})
+    >>> (client.host, client.port)
+    ('api.local', 8080)
+
+For details on all supported behavior, see :class:`.FromConfigMixin` in the API
+reference.
+
 Docstring parsing
 -----------------
 

jsonargparse/__init__.py

@@ -47,6 +47,7 @@
     _core,
     _deprecated,
     _formatters,
+    _from_config,
     _jsonnet,
     _jsonschema,
     _link_arguments,
@@ -61,6 +62,7 @@
 __all__ += _cli.__all__
 __all__ += _core.__all__
 __all__ += _signatures.__all__
+__all__ += _from_config.__all__
 __all__ += _link_arguments.__all__
 __all__ += _subcommands.__all__
 __all__ += _jsonschema.__all__

jsonargparse/_from_config.py

@@ -32,9 +32,9 @@ class FromConfigMixin:
            based on a config file or dict.
 
     Attributes:
-        ``__from_config_init_defaults__``: Optional path to a config file for
+        __from_config_init_defaults__: Optional path to a config file for
             overriding ``__init__`` defaults.
-        ``__from_config_parser_kwargs__``: Additional kwargs to pass to the
+        __from_config_parser_kwargs__: Additional kwargs to pass to the
             ArgumentParser used for parsing configs.
     """