Merge pull request #8771 from tk0miya/759_preserve_defaults

Fix #759: autodoc: Add sphinx.ext.autodoc.preserve_defaults extension

CHANGES

@@ -192,6 +192,9 @@ Features added
 * #8775: autodoc: Support type union operator (PEP-604) in Python 3.10 or above
 * #8297: autodoc: Allow to extend :confval:`autodoc_default_options` via
   directive options
+* #759: autodoc: Add a new configuration :confval:`autodoc_preserve_defaults` as
+  an experimental feature.  It preserves the default argument values of
+  functions in source code and keep them not evaluated for readability.
 * #8619: html: kbd role generates customizable HTML tags for compound keys
 * #8634: html: Allow to change the order of JS/CSS via ``priority`` parameter
   for :meth:`Sphinx.add_js_file()` and :meth:`Sphinx.add_css_file()`

doc/usage/extensions/autodoc.rst

@@ -586,6 +586,16 @@ There are also config values that you can set:
    .. __: https://mypy.readthedocs.io/en/latest/kinds_of_types.html#type-aliases
    .. versionadded:: 3.3
 
+.. confval:: autodoc_preserve_defaults
+
+   If True, the default argument values of functions will be not evaluated on
+   generating document.  It preserves them as is in the source code.
+
+   .. versionadded:: 4.0
+
+      Added as an experimental feature.  This will be integrated into autodoc core
+      in the future.
+
 .. confval:: autodoc_warningiserror
 
    This value controls the behavior of :option:`sphinx-build -W` during

sphinx/ext/autodoc/__init__.py

@@ -2634,6 +2634,7 @@ def setup(app: Sphinx) -> Dict[str, Any]:
 
     app.connect('config-inited', migrate_autodoc_member_order, priority=800)
 
+    app.setup_extension('sphinx.ext.autodoc.preserve_defaults')
     app.setup_extension('sphinx.ext.autodoc.type_comment')
     app.setup_extension('sphinx.ext.autodoc.typehints')
 

sphinx/ext/autodoc/preserve_defaults.py

@@ -0,0 +1,88 @@
+"""
+    sphinx.ext.autodoc.preserve_defaults
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Preserve the default argument values of function signatures in source code
+    and keep them not evaluated for readability.
+
+    :copyright: Copyright 2007-2021 by the Sphinx team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+import ast
+import inspect
+from typing import Any, Dict
+
+from sphinx.application import Sphinx
+from sphinx.locale import __
+from sphinx.pycode.ast import parse as ast_parse
+from sphinx.pycode.ast import unparse as ast_unparse
+from sphinx.util import logging
+
+logger = logging.getLogger(__name__)
+
+
+class DefaultValue:
+    def __init__(self, name: str) -> None:
+        self.name = name
+
+    def __repr__(self) -> str:
+        return self.name
+
+
+def get_function_def(obj: Any) -> ast.FunctionDef:
+    """Get FunctionDef object from living object.
+    This tries to parse original code for living object and returns
+    AST node for given *obj*.
+    """
+    try:
+        source = inspect.getsource(obj)
+        if source.startswith((' ', r'\t')):
+            # subject is placed inside class or block.  To read its docstring,
+            # this adds if-block before the declaration.
+            module = ast_parse('if True:\n' + source)
+            return module.body[0].body[0]  # type: ignore
+        else:
+            module = ast_parse(source)
+            return module.body[0]  # type: ignore
+    except (OSError, TypeError):  # failed to load source code
+        return None
+
+
+def update_defvalue(app: Sphinx, obj: Any, bound_method: bool) -> None:
+    """Update defvalue info of *obj* using type_comments."""
+    if not app.config.autodoc_preserve_defaults:
+        return
+
+    try:
+        function = get_function_def(obj)
+        if function.args.defaults or function.args.kw_defaults:
+            sig = inspect.signature(obj)
+            defaults = list(function.args.defaults)
+            kw_defaults = list(function.args.kw_defaults)
+            parameters = list(sig.parameters.values())
+            for i, param in enumerate(parameters):
+                if param.default is not param.empty:
+                    if param.kind in (param.POSITIONAL_ONLY, param.POSITIONAL_OR_KEYWORD):
+                        value = DefaultValue(ast_unparse(defaults.pop(0)))  # type: ignore
+                        parameters[i] = param.replace(default=value)
+                    else:
+                        value = DefaultValue(ast_unparse(kw_defaults.pop(0)))  # type: ignore
+                        parameters[i] = param.replace(default=value)
+            sig = sig.replace(parameters=parameters)
+            obj.__signature__ = sig
+    except (AttributeError, TypeError):
+        # failed to update signature (ex. built-in or extension types)
+        pass
+    except NotImplementedError as exc:  # failed to ast.unparse()
+        logger.warning(__("Failed to parse a default argument value for %r: %s"), obj, exc)
+
+
+def setup(app: Sphinx) -> Dict[str, Any]:
+    app.add_config_value('autodoc_preserve_defaults', False, True)
+    app.connect('autodoc-before-process-signature', update_defvalue)
+
+    return {
+        'version': '1.0',
+        'parallel_read_safe': True
+    }

tests/roots/test-ext-autodoc/target/preserve_defaults.py

@@ -0,0 +1,19 @@
+from datetime import datetime
+from typing import Any
+
+CONSTANT = 'foo'
+SENTINEL = object()
+
+
+def foo(name: str = CONSTANT,
+        sentinal: Any = SENTINEL,
+        now: datetime = datetime.now()) -> None:
+    """docstring"""
+
+
+class Class:
+    """docstring"""
+
+    def meth(self, name: str = CONSTANT, sentinal: Any = SENTINEL,
+             now: datetime = datetime.now()) -> None:
+        """docstring"""

tests/test_ext_autodoc_preserve_defaults.py

@@ -0,0 +1,45 @@
+"""
+    test_ext_autodoc_preserve_defaults
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    Test the autodoc extension.
+
+    :copyright: Copyright 2007-2021 by the Sphinx team, see AUTHORS.
+    :license: BSD, see LICENSE for details.
+"""
+
+import pytest
+
+from .test_ext_autodoc import do_autodoc
+
+
+@pytest.mark.sphinx('html', testroot='ext-autodoc',
+                    confoverrides={'autodoc_preserve_defaults': True})
+def test_preserve_defaults(app):
+    options = {"members": None}
+    actual = do_autodoc(app, 'module', 'target.preserve_defaults', options)
+    assert list(actual) == [
+        '',
+        '.. py:module:: target.preserve_defaults',
+        '',
+        '',
+        '.. py:class:: Class()',
+        '   :module: target.preserve_defaults',
+        '',
+        '   docstring',
+        '',
+        '',
+        '   .. py:method:: Class.meth(name: str = CONSTANT, sentinal: Any = SENTINEL, '
+        'now: datetime.datetime = datetime.now()) -> None',
+        '      :module: target.preserve_defaults',
+        '',
+        '      docstring',
+        '',
+        '',
+        '.. py:function:: foo(name: str = CONSTANT, sentinal: Any = SENTINEL, now: '
+        'datetime.datetime = datetime.now()) -> None',
+        '   :module: target.preserve_defaults',
+        '',
+        '   docstring',
+        '',
+    ]