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

@@ -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)
 

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