From 0fe458ecc46d2f2a2e82e324d860dff932d848d4 Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Mon, 18 Sep 2023 06:56:19 -0700
Subject: [PATCH] gh-108843: fix ast.unparse for f-string with many quotes
 (#108981)

---
 Lib/ast.py                                    | 21 ++++++++++++++++++-
 Lib/test/test_unparse.py                      | 14 +++++++++++++
 ...-09-06-06-17-23.gh-issue-108843.WJMhsS.rst |  1 +
 3 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-09-06-06-17-23.gh-issue-108843.WJMhsS.rst

diff --git a/Lib/ast.py b/Lib/ast.py
index 17ec7ff6f8bc12..1f54309c8450d8 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -1236,17 +1236,36 @@ def visit_JoinedStr(self, node):
 
         new_fstring_parts = []
         quote_types = list(_ALL_QUOTES)
+        fallback_to_repr = False
         for value, is_constant in fstring_parts:
             if is_constant:
-                value, quote_types = self._str_literal_helper(
+                value, new_quote_types = self._str_literal_helper(
                     value,
                     quote_types=quote_types,
                     escape_special_whitespace=True,
                 )
+                if set(new_quote_types).isdisjoint(quote_types):
+                    fallback_to_repr = True
+                    break
+                quote_types = new_quote_types
             elif "\n" in value:
                 quote_types = [q for q in quote_types if q in _MULTI_QUOTES]
+                assert quote_types
             new_fstring_parts.append(value)
 
+        if fallback_to_repr:
+            # If we weren't able to find a quote type that works for all parts
+            # of the JoinedStr, fallback to using repr and triple single quotes.
+            quote_types = ["'''"]
+            new_fstring_parts.clear()
+            for value, is_constant in fstring_parts:
+                if is_constant:
+                    value = repr('"' + value)  # force repr to use single quotes
+                    expected_prefix = "'\""
+                    assert value.startswith(expected_prefix), repr(value)
+                    value = value[len(expected_prefix):-1]
+                new_fstring_parts.append(value)
+
         value = "".join(new_fstring_parts)
         quote_type = quote_types[0]
         self.write(f"{quote_type}{value}{quote_type}")
diff --git a/Lib/test/test_unparse.py b/Lib/test/test_unparse.py
index 38c59e6d430b58..bdf7b0588bee67 100644
--- a/Lib/test/test_unparse.py
+++ b/Lib/test/test_unparse.py
@@ -635,6 +635,20 @@ def test_star_expr_assign_target_multiple(self):
         self.check_src_roundtrip("[a, b] = [c, d] = [e, f] = g")
         self.check_src_roundtrip("a, b = [c, d] = e, f = g")
 
+    def test_multiquote_joined_string(self):
+        self.check_ast_roundtrip("f\"'''{1}\\\"\\\"\\\"\" ")
+        self.check_ast_roundtrip("""f"'''{1}""\\"" """)
+        self.check_ast_roundtrip("""f'""\"{1}''' """)
+        self.check_ast_roundtrip("""f'""\"{1}""\\"' """)
+
+        self.check_ast_roundtrip("""f"'''{"\\n"}""\\"" """)
+        self.check_ast_roundtrip("""f'""\"{"\\n"}''' """)
+        self.check_ast_roundtrip("""f'""\"{"\\n"}""\\"' """)
+
+        self.check_ast_roundtrip("""f'''""\"''\\'{"\\n"}''' """)
+        self.check_ast_roundtrip("""f'''""\"''\\'{"\\n\\"'"}''' """)
+        self.check_ast_roundtrip("""f'''""\"''\\'{""\"\\n\\"'''""\" '''\\n'''}''' """)
+
 
 class ManualASTCreationTestCase(unittest.TestCase):
     """Test that AST nodes created without a type_params field unparse correctly."""
diff --git a/Misc/NEWS.d/next/Library/2023-09-06-06-17-23.gh-issue-108843.WJMhsS.rst b/Misc/NEWS.d/next/Library/2023-09-06-06-17-23.gh-issue-108843.WJMhsS.rst
new file mode 100644
index 00000000000000..0f15761c14bb7d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-09-06-06-17-23.gh-issue-108843.WJMhsS.rst
@@ -0,0 +1 @@
+Fix an issue in :func:`ast.unparse` when unparsing f-strings containing many quote types.