[clang-tidy][test] Allow specifying potentially unused suffixes

[njames93]

Summary

If a check-suffix is only required for a CHECK-FIXES or CHECK-MESSAGES. check_clang_tidy will pass the prefixes CHECK-FIXES<...> and CHECK-MESSAGES<...> to FileCheck.
This will result in a FileCheck failing because of an unused prefix.

This addresses the problem by not passing unused prefixes. Its also possible to fix this be passing --allow-unused-prefixes flag to FileCheck, but seeing as we have already done the legwork in the script to see its unused, this fix seems the better way to go.

[aaron.ballman]

LGTM, thanks!

clang-tools-extra/test/clang-tidy/check_clang_tidy.py

for check in args.check_suffix:
     if not has_check_fix and not has_check_message and not has_check_note:
       sys.exit('%s, %s or %s not found in the input' %
         (check_fixes_prefix, check_messages_prefix, check_notes_prefix))
 
     has_check_fixes = has_check_fixes or has_check_fix
     has_check_messages = has_check_messages or has_check_message
     has_check_notes = has_check_notes or has_check_note
 
+    if has_check_fix:
       check_fixes_prefixes.append(check_fixes_prefix)
+    if has_check_message:
       check_messages_prefixes.append(check_messages_prefix)
+    if has_check_note:
       check_notes_prefixes.append(check_notes_prefix)
 
   assert has_check_fixes or has_check_messages or has_check_notes
   # Remove the contents of the CHECK lines to avoid CHECKs matching on
   # themselves.  We need to keep the comments to preserve line numbers while
   # avoiding empty lines which could potentially trigger formatting-related
   # checks.
   cleaned_test = re.sub('// *CHECK-[A-Z0-9\-]*:[^\r\n]*', '//', input_text)
 

clang-tools-extra/test/clang-tidy/checkers/modernize-loop-convert-reverse.cpp

 // Ensure we get a warning if we supply the header argument without the
 // function argument.
 // RUN: clang-tidy %s -checks=-*,modernize-loop-convert -config="{CheckOptions: [ \
 // RUN:   {key: modernize-loop-convert.MakeReverseRangeHeader, value: 'llvm/ADT/STLExtras.h'}]}" \
 // RUN: -- -std=c++17 2>&1 \
 // RUN:   | FileCheck %s -check-prefix=CHECK-HEADER-NO-FUNC \
 // RUN:       -implicit-check-not="{{warning|error}}:"
 
-/// Suppress FileCheck --allow-unused-prefixes=false diagnostics.
-// CHECK-MESSAGES-RANGES: {{^}}
-// CHECK-MESSAGES-CUSTOM: {{^}}
-// CHECK-MESSAGES-CUSTOM-SYS: {{^}}
-// CHECK-MESSAGES-CUSTOM-NO-SYS: {{^}}
-// CHECK-MESSAGES-CUSTOM-NO-HEADER: {{^}}
-
 // CHECK-HEADER-NO-FUNC: warning: modernize-loop-convert: 'MakeReverseRangeHeader' is set but 'MakeReverseRangeFunction' is not, disabling reverse loop transformation
 
 // Make sure appropiate headers are included
 // CHECK-FIXES-RANGES: #include <ranges>
 // CHECK-FIXES-CUSTOM-NO-SYS: #include "llvm/ADT/STLExtras.h"
 // CHECK-FIXES-CUSTOM-SYS: #include <llvm/ADT/STLExtras.h>
 
 // Make sure no header is included in this example