Preserve visible quote types for f-string debug expressions

CHANGES.md

@@ -19,6 +19,8 @@
   indented less (#3964)
 - Multiline list and dict unpacking as the sole argument to a function is now also
   indented less (#3992)
+- In f-string debug expressions preserve quote types that are visible in the final
+  string (#4005)
 - Keep requiring two empty lines between module-level docstring and first function or
   class definition. (#4028)
 

src/black/trans.py

@@ -590,11 +590,22 @@ 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] + 1 : span[1] - 1]  # +-1 to get rid of curly braces
+                    for span in iter_fexpr_spans(string)
+                )
+                debug_expressions_contain_visible_quotes = any(
+                    re.search(r".*[\'\"].*(?<![!:=])={1}(?!=)(?![^\s:])", expression)
+                    for expression in f_expressions
+                )
+                if not debug_expressions_contain_visible_quotes:
+                    # We don't want to toggle visible 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 +305,27 @@ 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"]} {foo("bar",x=123)} {"foo" != "bar"} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}')
+
+log.info(f'Skipping: {desc["db_id"]} {foo("bar",x=123)=} {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: {"a" == "b" == "c" == "d"} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}')
+
+log.info(f'Skipping: {"a" == "b" == "c" == "d"=} {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 }')
+
+log.info(f'''Skipping: {"a" == 'b'} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}''')
+
+log.info(f'''Skipping: {'a' == "b"=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}''')
+
+log.info(f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}""")
 
 # output
 
@@ -846,3 +867,55 @@ 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']} {foo('bar',x=123)} {'foo' != 'bar'} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"
+)
+
+log.info(
+    "Skipping:"
+    f' {desc["db_id"]} {foo("bar",x=123)=} {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" {'a' == 'b' == 'c' == 'd'} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"
+)
+
+log.info(
+    "Skipping:"
+    f' {"a" == "b" == "c" == "d"=} {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 }'
+)
+
+log.info(
+    f"""Skipping: {"a" == 'b'} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
+)
+
+log.info(
+    f"""Skipping: {'a' == "b"=} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
+)
+
+log.info(
+    f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"""
+)