1 files changed, 49 insertions, 0 deletions
diff --git a/sphinx/util/inspect.py b/sphinx/util/inspect.py
index 80cac97d9..7c977daf1 100644
--- a/sphinx/util/inspect.py
+++ b/sphinx/util/inspect.py
@@ -21,8 +21,11 @@ from inspect import (  # NOQA
 )
 from io import StringIO
 from typing import Any, Callable, Mapping, List, Tuple
+from typing import cast
 
 from sphinx.deprecation import RemovedInSphinx40Warning, RemovedInSphinx50Warning
+from sphinx.pycode.ast import ast  # for py35-37
+from sphinx.pycode.ast import unparse as ast_unparse
 from sphinx.util import logging
 from sphinx.util.typing import stringify as stringify_annotation
 
@@ -429,6 +432,52 @@ def stringify_signature(sig: inspect.Signature, show_annotation: bool = True,
         return '(%s) -> %s' % (', '.join(args), annotation)
 
 
+def signature_from_str(signature: str) -> inspect.Signature:
+    """Create a Signature object from string."""
+    module = ast.parse('def func' + signature + ': pass')
+    definition = cast(ast.FunctionDef, module.body[0])  # type: ignore
+
+    # parameters
+    args = definition.args
+    params = []
+
+    if hasattr(args, "posonlyargs"):
+        for arg in args.posonlyargs:  # type: ignore
+            annotation = ast_unparse(arg.annotation) or Parameter.empty
+            params.append(Parameter(arg.arg, Parameter.POSITIONAL_ONLY,
+                                    annotation=annotation))
+
+    for i, arg in enumerate(args.args):
+        if len(args.args) - i <= len(args.defaults):
+            default = ast_unparse(args.defaults[-len(args.args) + i])
+        else:
+            default = Parameter.empty
+
+        annotation = ast_unparse(arg.annotation) or Parameter.empty
+        params.append(Parameter(arg.arg, Parameter.POSITIONAL_OR_KEYWORD,
+                                default=default, annotation=annotation))
+
+    if args.vararg:
+        annotation = ast_unparse(args.vararg.annotation) or Parameter.empty
+        params.append(Parameter(args.vararg.arg, Parameter.VAR_POSITIONAL,
+                                annotation=annotation))
+
+    for i, arg in enumerate(args.kwonlyargs):
+        default = ast_unparse(args.kw_defaults[i])
+        annotation = ast_unparse(arg.annotation) or Parameter.empty
+        params.append(Parameter(arg.arg, Parameter.KEYWORD_ONLY, default=default,
+                                annotation=annotation))
+
+    if args.kwarg:
+        annotation = ast_unparse(args.kwarg.annotation) or Parameter.empty
+        params.append(Parameter(args.kwarg.arg, Parameter.VAR_KEYWORD,
+                                annotation=annotation))
+
+    return_annotation = ast_unparse(definition.returns) or Parameter.empty
+
+    return inspect.Signature(params, return_annotation=return_annotation)
+
+
 class Signature:
     """The Signature object represents the call signature of a callable object and
     its return annotation.