From 0b32e72635f6e117824b5cba3b8b38254a6a2644 Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Sun, 4 Oct 2020 01:45:47 +0900
Subject: [PATCH] pycode: ast.unparse() construct number literals using source
 code

Developers can write number literals in several ways. For example,
decimal (1234), hexadecimal (0x1234), octal decimal (0o1234) and so on.
But, AST module don't mind how the numbers written in the code. As a
result, ast.unparse() could not reproduce the original form of number
literals.

This allows to construct number literals as possible using original
source code.

Note: This is only available in Python 3.8+.
---
 sphinx/pycode/ast.py     | 11 +++++++++--
 tests/test_pycode_ast.py | 14 +++++++++-----
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/sphinx/pycode/ast.py b/sphinx/pycode/ast.py
index 2583448d5..17d78f4eb 100644
--- a/sphinx/pycode/ast.py
+++ b/sphinx/pycode/ast.py
@@ -58,17 +58,19 @@ def parse(code: str, mode: str = 'exec') -> "ast.AST":
         return ast.parse(code, mode=mode)
 
 
-def unparse(node: Optional[ast.AST]) -> Optional[str]:
+def unparse(node: Optional[ast.AST], code: str = '') -> Optional[str]:
     """Unparse an AST to string."""
     if node is None:
         return None
     elif isinstance(node, str):
         return node
-    return _UnparseVisitor().visit(node)
+    return _UnparseVisitor(code).visit(node)
 
 
 # a greatly cut-down version of `ast._Unparser`
 class _UnparseVisitor(ast.NodeVisitor):
+    def __init__(self, code: str = '') -> None:
+        self.code = code
 
     def _visit_op(self, node: ast.AST) -> str:
         return OPERATORS[node.__class__]
@@ -195,6 +197,11 @@ class _UnparseVisitor(ast.NodeVisitor):
         def visit_Constant(self, node: ast.Constant) -> str:
             if node.value is Ellipsis:
                 return "..."
+            elif isinstance(node.value, (int, float, complex)):
+                if self.code and sys.version_info > (3, 8):
+                    return ast.get_source_segment(self.code, node)
+                else:
+                    return repr(node.value)
             else:
                 return repr(node.value)
 
diff --git a/tests/test_pycode_ast.py b/tests/test_pycode_ast.py
index 32a784b74..bbff64dd0 100644
--- a/tests/test_pycode_ast.py
+++ b/tests/test_pycode_ast.py
@@ -58,7 +58,7 @@ from sphinx.pycode import ast
 ])
 def test_unparse(source, expected):
     module = ast.parse(source)
-    assert ast.unparse(module.body[0].value) == expected
+    assert ast.unparse(module.body[0].value, source) == expected
 
 
 def test_unparse_None():
@@ -66,8 +66,12 @@ def test_unparse_None():
 
 
 @pytest.mark.skipif(sys.version_info < (3, 8), reason='python 3.8+ is required.')
-def test_unparse_py38():
-    source = "lambda x=0, /, y=1, *args, z, **kwargs: x + y + z"
-    expected = "lambda x=0, /, y=1, *args, z, **kwargs: ..."
+@pytest.mark.parametrize('source,expected', [
+    ("lambda x=0, /, y=1, *args, z, **kwargs: x + y + z",
+     "lambda x=0, /, y=1, *args, z, **kwargs: ..."),    # posonlyargs
+    ("0x1234", "0x1234"),                               # Constant
+    ("1_000_000", "1_000_000"),                         # Constant
+])
+def test_unparse_py38(source, expected):
     module = ast.parse(source)
-    assert ast.unparse(module.body[0].value) == expected
+    assert ast.unparse(module.body[0].value, source) == expected