[clang-tidy] support expect no diagnosis test (llvm#91293)

When someone wants to declare a test case without any diagnosis.
check-clang-tidy will failed with error message

```
CHECK-FIXES, CHECK-MESSAGES or CHECK-NOTES not found in the input
```

This PR want to check there are no diagnosis from clang-tidy when
CHECK-FIXES, CHECK-MESSAGES or CHECK-NOTES are not found.

It also changes the extension of a test case. `hxx` is not a valid test
case extension and won't be tested.

---------

Co-authored-by: Danny Mösch <danny.moesch@icloud.com>

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

@@ -99,6 +99,7 @@ def __init__(self, args, extra_args):
  self.has_check_fixes = False
  self.has_check_messages = False
  self.has_check_notes = False
+ self.expect_no_diagnosis = False
  self.export_fixes = args.export_fixes
  self.fixes = MessagePrefix("CHECK-FIXES")
  self.messages = MessagePrefix("CHECK-MESSAGES")
@@ -172,12 +173,21 @@ def get_prefixes(self):
  )
 
  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"
- % (self.fixes.prefix, self.messages.prefix, self.notes.prefix)
- )
+ self.expect_no_diagnosis = True
 
- assert self.has_check_fixes or self.has_check_messages or self.has_check_notes
+ expect_diagnosis = (
+ self.has_check_fixes or self.has_check_messages or self.has_check_notes
+ )
+ if self.expect_no_diagnosis and expect_diagnosis:
+ sys.exit(
+ "%s, %s or %s not found in the input"
+ % (
+ self.fixes.prefix,
+ self.messages.prefix,
+ self.notes.prefix,
+ )
+ )
+ assert expect_diagnosis or self.expect_no_diagnosis
 
  def prepare_test_inputs(self):
  # Remove the contents of the CHECK lines to avoid CHECKs matching on
@@ -226,6 +236,10 @@ def run_clang_tidy(self):
  print("------------------------------------------------------------------")
  return clang_tidy_output
 
+ def check_no_diagnosis(self, clang_tidy_output):
+ if clang_tidy_output != "":
+ sys.exit("No diagnostics were expected, but found the ones above")
+
  def check_fixes(self):
  if self.has_check_fixes:
  try_run(
@@ -277,7 +291,9 @@ def run(self):
  self.get_prefixes()
  self.prepare_test_inputs()
  clang_tidy_output = self.run_clang_tidy()
- if self.export_fixes is None:
+ if self.expect_no_diagnosis:
+ self.check_no_diagnosis(clang_tidy_output)
+ elif self.export_fixes is None:
  self.check_fixes()
  self.check_messages(clang_tidy_output)
  self.check_notes(clang_tidy_output)

clang-tools-extra/test/clang-tidy/checkers/misc/unused-using-decls.hpp

@@ -0,0 +1,6 @@
+// RUN: %check_clang_tidy %s misc-unused-using-decls %t
+
+// Verify that we don't generate the warnings on header files.
+namespace foo { class Foo {}; }
+
+using foo::Foo;