[Python-checkins] bpo-38870: Do not separate factor prefixes in ast.unparse (GH-20133)

[Batuhan Taskaya]

https://github.com/python/cpython/commit/ce4a753dcb3eef3d68e892a6515490b1aa219651
commit: ce4a753dcb3eef3d68e892a6515490b1aa219651
branch: master
author: Batuhan Taskaya <batuhanosmantaskaya at gmail.com>
committer: GitHub <noreply at github.com>
date: 2020-05-16T22:46:11+01:00
summary:

bpo-38870: Do not separate factor prefixes in ast.unparse (GH-20133)

files:
M Lib/ast.py
M Lib/test/test_unparse.py

diff --git a/Lib/ast.py b/Lib/ast.py
index 7a43581c0e6ce..1de37b9567ece 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -1190,10 +1190,10 @@ def visit_Tuple(self, node):
 
     unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
     unop_precedence = {
-        "~": _Precedence.FACTOR,
         "not": _Precedence.NOT,
+        "~": _Precedence.FACTOR,
         "+": _Precedence.FACTOR,
-        "-": _Precedence.FACTOR
+        "-": _Precedence.FACTOR,
     }
 
     def visit_UnaryOp(self, node):
@@ -1201,7 +1201,10 @@ def visit_UnaryOp(self, node):
         operator_precedence = self.unop_precedence[operator]
         with self.require_parens(operator_precedence, node):
             self.write(operator)
-            self.write(" ")
+            # factor prefixes (+, -, ~) shouldn't be seperated
+            # from the value they belong, (e.g: +1 instead of + 1)
+            if operator_precedence is not _Precedence.FACTOR:
+                self.write(" ")
             self.set_precedence(operator_precedence, node.operand)
             self.traverse(node.operand)
 
diff --git a/Lib/test/test_unparse.py b/Lib/test/test_unparse.py
index 2be44b246aa69..1393bcce741c9 100644
--- a/Lib/test/test_unparse.py
+++ b/Lib/test/test_unparse.py
@@ -347,7 +347,7 @@ def test_simple_expressions_parens(self):
         self.check_src_roundtrip("(1 + 2) / 3")
         self.check_src_roundtrip("(1 + 2) * 3 + 4 * (5 + 2)")
         self.check_src_roundtrip("(1 + 2) * 3 + 4 * (5 + 2) ** 2")
-        self.check_src_roundtrip("~ x")
+        self.check_src_roundtrip("~x")
         self.check_src_roundtrip("x and y")
         self.check_src_roundtrip("x and y and z")
         self.check_src_roundtrip("x and (y and x)")
@@ -401,6 +401,12 @@ def test_docstrings_negative_cases(self):
                 self.check_ast_roundtrip(src)
                 self.check_src_dont_roundtrip(src)
 
+    def test_unary_op_factor(self):
+        for prefix in ("+", "-", "~"):
+            self.check_src_roundtrip(f"{prefix}1")
+        for prefix in ("not",):
+            self.check_src_roundtrip(f"{prefix} 1")
+
 class DirectoryTestCase(ASTTestCase):
     """Test roundtrip behaviour on all files in Lib and Lib/test."""