Use line breaks FTW in output directive error message

Author: erlend-aasland

Lib/test/test_clinic.py

@@ -634,13 +634,24 @@ def test_directive_preserve_output(self):
         self.assertEqual(generated, block)
 
     def test_directive_output_invalid_command(self):
-        err = (
-            "Invalid command / destination name 'cmd', must be one of:\n"
-            "preset push pop print everything cpp_if docstring_prototype "
-            "docstring_definition methoddef_define impl_prototype "
-            "parser_prototype parser_definition cpp_endif methoddef_ifndef "
-            "impl_definition"
-        )
+        err = dedent("""
+            Invalid command or destination name 'cmd'. Must be one of:
+             - preset
+             - push
+             - pop
+             - print
+             - everything
+             - cpp_if
+             - docstring_prototype
+             - docstring_definition
+             - methoddef_define
+             - impl_prototype
+             - parser_prototype
+             - parser_definition
+             - cpp_endif
+             - methoddef_ifndef
+             - impl_definition
+        """).strip()
         block = """
             /*[clinic input]
             output cmd buffer

Tools/clinic/clinic.py

@@ -4567,8 +4567,10 @@ def directive_output(
             return
 
         if command_or_name not in fd:
-            fail(f"Invalid command / destination name {command_or_name!r}, must be one of:\n"
-                 "preset push pop print everything", " ".join(fd))
+            allowed = ["preset", "push", "pop", "print", "everything"]
+            allowed.extend(fd)
+            fail(f"Invalid command or destination name {command_or_name!r}. "
+                 "Must be one of:\n -", "\n - ".join(allowed))
         fd[command_or_name] = d
 
     def directive_dump(self, name: str) -> None: