gh-108469: Update ast.unparse for unescaped quote support from PEP701 [3.12] (#108553)

Co-authored-by: sunmy2019 <59365878+sunmy2019@users.noreply.github.com>

1 files changed, 10 insertions, 21 deletions

diff --git a/Lib/ast.py b/Lib/ast.py
index 45b95963f81..17ec7ff6f8b 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -1225,17 +1225,7 @@ class _Unparser(NodeVisitor):
 
     def visit_JoinedStr(self, node):
         self.write("f")
-        if self._avoid_backslashes:
-            with self.buffered() as buffer:
-                self._write_fstring_inner(node)
-            return self._write_str_avoiding_backslashes("".join(buffer))
-
-        # If we don't need to avoid backslashes globally (i.e., we only need
-        # to avoid them inside FormattedValues), it's cosmetically preferred
-        # to use escaped whitespace. That is, it's preferred to use backslashes
-        # for cases like: f"{x}\n". To accomplish this, we keep track of what
-        # in our buffer corresponds to FormattedValues and what corresponds to
-        # Constant parts of the f-string, and allow escapes accordingly.
+
         fstring_parts = []
         for value in node.values:
             with self.buffered() as buffer:
@@ -1247,11 +1237,14 @@ class _Unparser(NodeVisitor):
         new_fstring_parts = []
         quote_types = list(_ALL_QUOTES)
         for value, is_constant in fstring_parts:
-            value, quote_types = self._str_literal_helper(
-                value,
-                quote_types=quote_types,
-                escape_special_whitespace=is_constant,
-            )
+            if is_constant:
+                value, quote_types = self._str_literal_helper(
+                    value,
+                    quote_types=quote_types,
+                    escape_special_whitespace=True,
+                )
+            elif "\n" in value:
+                quote_types = [q for q in quote_types if q in _MULTI_QUOTES]
             new_fstring_parts.append(value)
 
         value = "".join(new_fstring_parts)
@@ -1273,16 +1266,12 @@ class _Unparser(NodeVisitor):
 
     def visit_FormattedValue(self, node):
         def unparse_inner(inner):
-            unparser = type(self)(_avoid_backslashes=True)
+            unparser = type(self)()
             unparser.set_precedence(_Precedence.TEST.next(), inner)
             return unparser.visit(inner)
 
         with self.delimit("{", "}"):
             expr = unparse_inner(node.value)
-            if "\\" in expr:
-                raise ValueError(
-                    "Unable to avoid backslash in f-string expression part"
-                )
             if expr.startswith("{"):
                 # Separate pair of opening brackets as "{ {"
                 self.write(" ")