Fix #6165: autodoc: `tab_width` setting of docutils has been ignored

CHANGES

@@ -91,6 +91,7 @@ Bugs fixed
 * #6213: ifconfig: contents after headings are not shown
 * commented term in glossary directive is wrongly recognized
 * #6299: rst domain: rst:directive directive generates waste space
+* #6165: autodoc: ``tab_width`` setting of docutils has been ignored
 
 Testing
 --------

sphinx/ext/autodoc/__init__.py

@@ -442,7 +442,8 @@ class Documenter:
         docstring = getdoc(self.object, self.get_attr,
                            self.env.config.autodoc_inherit_docstrings)
         if docstring:
-            return [prepare_docstring(docstring, ignore)]
+            tab_width = self.directive.state.document.settings.tab_width
+            return [prepare_docstring(docstring, ignore, tab_width)]
         return []
 
     def process_doc(self, docstrings):
@@ -936,7 +937,9 @@ class DocstringSignatureMixin:
             if base not in valid_names:
                 continue
             # re-prepare docstring to ignore more leading indentation
-            self._new_docstrings[i] = prepare_docstring('\n'.join(doclines[1:]))
+            tab_width = self.directive.state.document.settings.tab_width  # type: ignore
+            self._new_docstrings[i] = prepare_docstring('\n'.join(doclines[1:]),
+                                                        tabsize=tab_width)
             result = args, retann
             # don't look any further
             break
@@ -1179,7 +1182,9 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
                     docstrings = [initdocstring]
                 else:
                     docstrings.append(initdocstring)
-        return [prepare_docstring(docstring, ignore) for docstring in docstrings]
+
+        tab_width = self.directive.state.document.settings.tab_width
+        return [prepare_docstring(docstring, ignore, tab_width) for docstring in docstrings]
 
     def add_content(self, more_content, no_docstring=False):
         # type: (Any, bool) -> None

sphinx/ext/autodoc/directive.py

@@ -6,10 +6,14 @@
     :license: BSD, see LICENSE for details.
 """
 
+import warnings
+
 from docutils import nodes
+from docutils.parsers.rst.states import Struct
 from docutils.statemachine import StringList
 from docutils.utils import assemble_option_dict
 
+from sphinx.deprecation import RemovedInSphinx40Warning
 from sphinx.ext.autodoc import Options, get_documenters
 from sphinx.util import logging
 from sphinx.util.docutils import SphinxDirective, switch_source_input
@@ -17,7 +21,7 @@ from sphinx.util.nodes import nested_parse_with_titles
 
 if False:
     # For type annotation
-    from typing import Callable, Dict, List, Set, Type  # NOQA
+    from typing import Any, Callable, Dict, List, Set, Type  # NOQA
     from docutils.parsers.rst.state import RSTState  # NOQA
     from docutils.utils import Reporter  # NOQA
     from sphinx.config import Config  # NOQA
@@ -50,8 +54,8 @@ class DummyOptionSpec(dict):
 class DocumenterBridge:
     """A parameters container for Documenters."""
 
-    def __init__(self, env, reporter, options, lineno):
-        # type: (BuildEnvironment, Reporter, Options, int) -> None
+    def __init__(self, env, reporter, options, lineno, state=None):
+        # type: (BuildEnvironment, Reporter, Options, int, Any) -> None
         self.env = env
         self.reporter = reporter
         self.genopt = options
@@ -59,6 +63,16 @@ class DocumenterBridge:
         self.filename_set = set()  # type: Set[str]
         self.result = StringList()
 
+        if state:
+            self.state = state
+        else:
+            # create fake object for self.state.document.settings.tab_width
+            warnings.warn('DocumenterBridge requires a state object on instantiation.',
+                          RemovedInSphinx40Warning)
+            settings = Struct(tab_width=8)
+            document = Struct(settings=settings)
+            self.state = Struct(document=document)
+
     def warn(self, msg):
         # type: (str) -> None
         logger.warning(msg, location=(self.env.docname, self.lineno))
@@ -131,7 +145,7 @@ class AutodocDirective(SphinxDirective):
             return []
 
         # generate the output
-        params = DocumenterBridge(self.env, reporter, documenter_options, lineno)
+        params = DocumenterBridge(self.env, reporter, documenter_options, lineno, self.state)
         documenter = doccls(params, self.arguments[0])
         documenter.generate(more_content=self.content)
         if not params.result:

sphinx/ext/autosummary/__init__.py

@@ -175,7 +175,7 @@ _app = None  # type: Sphinx
 class FakeDirective(DocumenterBridge):
     def __init__(self):
         # type: () -> None
-        super().__init__({}, None, Options(), 0)  # type: ignore
+        super().__init__({}, None, Options(), 0, None)  # type: ignore
 
 
 def get_documenter(app, obj, parent):
@@ -236,7 +236,7 @@ class Autosummary(SphinxDirective):
     def run(self):
         # type: () -> List[nodes.Node]
         self.bridge = DocumenterBridge(self.env, self.state.document.reporter,
-                                       Options(), self.lineno)
+                                       Options(), self.lineno, self.state)
 
         names = [x.strip().split()[0] for x in self.content
                  if x.strip() and re.search(r'^[~a-zA-Z_]', x.strip()[0])]

sphinx/util/docstrings.py

@@ -15,8 +15,8 @@ if False:
     from typing import List  # NOQA
 
 
-def prepare_docstring(s, ignore=1):
-    # type: (str, int) -> List[str]
+def prepare_docstring(s, ignore=1, tabsize=8):
+    # type: (str, int, int) -> List[str]
     """Convert a docstring into lines of parseable reST.  Remove common leading
     indentation, where the indentation of a given number of lines (usually just
     one) is ignored.
@@ -25,7 +25,7 @@ def prepare_docstring(s, ignore=1):
     ViewList (used as argument of nested_parse().)  An empty line is added to
     act as a separator between this docstring and following content.
     """
-    lines = s.expandtabs().splitlines()
+    lines = s.expandtabs(tabsize).splitlines()
     # Find minimum indentation of any non-blank lines after ignored lines.
     margin = sys.maxsize
     for line in lines[ignore:]:

tests/test_autodoc.py

@@ -11,6 +11,7 @@
 
 import platform
 import sys
+from unittest.mock import Mock
 from warnings import catch_warnings
 
 import pytest
@@ -36,7 +37,9 @@ def do_autodoc(app, objtype, name, options=None):
     app.env.temp_data.setdefault('docname', 'index')  # set dummy docname
     doccls = app.registry.documenters[objtype]
     docoptions = process_documenter_options(doccls, app.config, options)
-    bridge = DocumenterBridge(app.env, LoggingReporter(''), docoptions, 1)
+    state = Mock()
+    state.document.settings.tab_width = 8
+    bridge = DocumenterBridge(app.env, LoggingReporter(''), docoptions, 1, state)
     documenter = doccls(bridge, name)
     documenter.generate()
 
@@ -95,7 +98,9 @@ def setup_test():
         genopt = options,
         result = ViewList(),
         filename_set = set(),
+        state = Mock(),
     )
+    directive.state.document.settings.tab_width = 8
 
     processed_docstrings = []
     processed_signatures = []