Preserve visible quote types for f-string debug expressions

CHANGES.md

@@ -17,6 +17,7 @@
   indented less (#3964)
 - Multiline list and dict unpacking as the sole argument to a function is now also
   indented less (#3992)
+- Preserve printable quote types for debug f-strings (#4005)
 
 ### Configuration
 

src/black/trans.py

@@ -590,11 +590,21 @@ def make_naked(string: str, string_prefix: str) -> str:
             """
             assert_is_leaf_string(string)
             if "f" in string_prefix:
-                string = _toggle_fexpr_quotes(string, QUOTE)
-                # After quotes toggling, quotes in expressions won't be escaped
-                # because quotes can't be reused in f-strings. So we can simply
-                # let the escaping logic below run without knowing f-string
-                # expressions.
+                f_expressions = (
+                    string[span[0] : span[1]] for span in iter_fexpr_spans(string)
+                )
+                expressions_contain_printable_quotes = any(
+                    re.search(r".*[\'\"].*=", expression)
+                    for expression in f_expressions
+                )
+                if not expressions_contain_printable_quotes:
+                    # We don't want to toggle printable quotes in debug f-strings, as
+                    # that would modify the AST
+                    string = _toggle_fexpr_quotes(string, QUOTE)
+                    # After quotes toggling, quotes in expressions won't be escaped
+                    # because quotes can't be reused in f-strings. So we can simply
+                    # let the escaping logic below run without knowing f-string
+                    # expressions.
 
             RE_EVEN_BACKSLASHES = r"(?:(?<!\\)(?:\\\\)*)"
             naked_string = string[len(string_prefix) + 1 : -1]

tests/data/cases/preview_long_strings.py

@@ -305,6 +305,15 @@ def foo():
 # Test case of an outer string' parens enclose an inner string's parens.
 call(body=("%s %s" % ((",".join(items)), suffix)))
 
+log.info(f'Skipping: {desc["db_id"]=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]=} {desc["exposure_max"]=}')
+
+log.info(f"Skipping: {desc['db_id']=} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']=} {desc['exposure_max']=}")
+
+log.info(f'Skipping: {desc["db_id"]} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}')
+
+log.info(f'Skipping: {foo("asdf")=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}')
+
+log.info(f'Skipping: {  longer_longer_longer_longer_longer_longer_name   [ "db_id" ]      [ "another_key" ]   =  :  .3f }')
 
 # output
 
@@ -846,3 +855,28 @@ def foo():
 
 # Test case of an outer string' parens enclose an inner string's parens.
 call(body="%s %s" % (",".join(items), suffix))
+
+log.info(
+    "Skipping:"
+    f' {desc["db_id"]=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]=} {desc["exposure_max"]=}'
+)
+
+log.info(
+    "Skipping:"
+    f" {desc['db_id']=} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']=} {desc['exposure_max']=}"
+)
+
+log.info(
+    "Skipping:"
+    f" {desc['db_id']} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"
+)
+
+log.info(
+    "Skipping:"
+    f' {foo("asdf")=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}'
+)
+
+log.info(
+    "Skipping:"
+    f' {  longer_longer_longer_longer_longer_longer_name   [ "db_id" ]      [ "another_key" ]   =  :  .3f }'
+)