Fix SPLIT_ARGUMENTS_WHEN_COMMA_TERMINATED for one-item named argument…

… lists by taking precedence over SPLIT_BEFORE_NAMED_ASSIGNS (#1160)

By taking precedence over SPLIT_BEFORE_NAMED_ASSIGNS, turn

  r = f0(a=1,)

into

  r = f0(
      a=1,
  )

CHANGELOG.md

@@ -6,7 +6,9 @@
 ### Changes
 - Remove dependency on importlib-metadata
 - Remove dependency on tomli when using >= py311
-
+### Fixed
+- Fix SPLIT_ARGUMENTS_WHEN_COMMA_TERMINATED for one-item named argument lists
+  by taking precedence over SPLIT_BEFORE_NAMED_ASSIGNS.
 
 ## [0.40.2] 2023-09-22
 ### Changes

yapf/yapflib/format_decision_state.py

@@ -373,6 +373,16 @@ def SurroundedByParens(token):
 
     ###########################################################################
     # Argument List Splitting
+
+    if style.Get('SPLIT_ARGUMENTS_WHEN_COMMA_TERMINATED'):
+      # Split before arguments in a function call or definition if the
+      # arguments are terminated by a comma.
+      opening = _GetOpeningBracket(current)
+      if opening and opening.previous_token and opening.previous_token.is_name:
+        if previous.value in '(,':
+          if opening.matching_bracket.previous_token.value == ',':
+            return True
+
     if (style.Get('SPLIT_BEFORE_NAMED_ASSIGNS') and not current.is_comment and
         subtypes.DEFAULT_OR_NAMED_ASSIGN_ARG_LIST in current.subtypes):
       if (previous.value not in {'=', ':', '*', '**'} and
@@ -409,15 +419,6 @@ def SurroundedByParens(token):
         self._ArgumentListHasDictionaryEntry(current)):
       return True
 
-    if style.Get('SPLIT_ARGUMENTS_WHEN_COMMA_TERMINATED'):
-      # Split before arguments in a function call or definition if the
-      # arguments are terminated by a comma.
-      opening = _GetOpeningBracket(current)
-      if opening and opening.previous_token and opening.previous_token.is_name:
-        if previous.value in '(,':
-          if opening.matching_bracket.previous_token.value == ',':
-            return True
-
     if ((current.is_name or current.value in {'*', '**'}) and
         previous.value == ','):
       # If we have a function call within an argument list and it won't fit on

yapftests/reformatter_basic_test.py

@@ -2274,6 +2274,8 @@ def testSplittingArgumentsTerminatedByComma(self):
         r =f0 (1,  2,3,)
 
         r =f0 (1,)
+
+        r =f0 (a=1,)
     """)  # noqa
     expected_formatted_code = textwrap.dedent("""\
         function_name(argument_name_1=1, argument_name_2=2, argument_name_3=3)
@@ -2306,6 +2308,10 @@ def testSplittingArgumentsTerminatedByComma(self):
         r = f0(
             1,
         )
+
+        r = f0(
+            a=1,
+        )
     """)
 
     try: