[clang-tidy] Improve "-quiet" option by suppressing "xxx warnings generated" (#154012)

Before this change, `-quiet` mode in clang-tidy generated meaningless
messages `xxx warnings generated` in output:
```cpp
// main.cpp
#include <iostream>

int main() {
  std::cout << 42;
}
```
```console
> clang-tidy -checks='-*,readability-magic-numbers' -quiet main.cpp

82 warnings generated.
main.cpp:4:16: warning: 42 is a magic number; consider replacing it with a named constant [readability-magic-numbers]
    4 |   std::cout << 42;
      |                ^
```

As you can see, `82 warnings generated.` does not say much `quiet` mode,
this patch removes this message completely:

```console
> ./build/bin/clang-tidy -p build -checks='-*,readability-magic-numbers' -quiet main.cpp

main.cpp:4:16: warning: 42 is a magic number; consider replacing it with a named constant [readability-magic-numbers]
    4 |   std::cout << 42;
      |                ^
```

In contrast, when running without `quiet`, It gives some meaningful
information because we know how many messages were suppressed thus
calculating total messages count:
```console
> clang-tidy -checks='-*,readability-magic-numbers' main.cpp

82 warnings generated.
main.cpp:4:16: warning: 42 is a magic number; consider replacing it with a named constant [readability-magic-numbers]
    4 |   std::cout << 42;
      |                ^
Suppressed 81 warnings (81 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
```

Fixes #47042

Author: vbvictor

clang-tools-extra/clang-tidy/ClangTidy.cpp

@@ -544,7 +544,7 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
              ArrayRef<std::string> InputFiles,
              llvm::IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> BaseFS,
              bool ApplyAnyFix, bool EnableCheckProfile,
-             llvm::StringRef StoreCheckProfile) {
+             llvm::StringRef StoreCheckProfile, bool Quiet) {
   ClangTool Tool(Compilations, InputFiles,
                  std::make_shared<PCHContainerOperations>(), BaseFS);
 
@@ -581,8 +581,9 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
   class ActionFactory : public FrontendActionFactory {
   public:
     ActionFactory(ClangTidyContext &Context,
-                  IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> BaseFS)
-        : ConsumerFactory(Context, std::move(BaseFS)) {}
+                  IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> BaseFS,
+                  bool Quiet)
+        : ConsumerFactory(Context, std::move(BaseFS)), Quiet(Quiet) {}
     std::unique_ptr<FrontendAction> create() override {
       return std::make_unique<Action>(&ConsumerFactory);
     }
@@ -593,6 +594,8 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
                        DiagnosticConsumer *DiagConsumer) override {
       // Explicitly ask to define __clang_analyzer__ macro.
       Invocation->getPreprocessorOpts().SetUpStaticAnalyzer = true;
+      if (Quiet)
+        Invocation->getDiagnosticOpts().ShowCarets = false;
       return FrontendActionFactory::runInvocation(
           Invocation, Files, PCHContainerOps, DiagConsumer);
     }
@@ -611,9 +614,10 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
     };
 
     ClangTidyASTConsumerFactory ConsumerFactory;
+    bool Quiet;
   };
 
-  ActionFactory Factory(Context, std::move(BaseFS));
+  ActionFactory Factory(Context, std::move(BaseFS), Quiet);
   Tool.run(&Factory);
   return DiagConsumer.take();
 }

clang-tools-extra/clang-tidy/ClangTidy.h

@@ -94,7 +94,8 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
              ArrayRef<std::string> InputFiles,
              llvm::IntrusiveRefCntPtr<llvm::vfs::OverlayFileSystem> BaseFS,
              bool ApplyAnyFix, bool EnableCheckProfile = false,
-             llvm::StringRef StoreCheckProfile = StringRef());
+             llvm::StringRef StoreCheckProfile = StringRef(),
+             bool Quiet = false);
 
 /// Controls what kind of fixes clang-tidy is allowed to apply.
 enum FixBehaviour {

clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp

@@ -717,7 +717,7 @@ int clangTidyMain(int argc, const char **argv) {
                            EnableModuleHeadersParsing);
   std::vector<ClangTidyError> Errors =
       runClangTidy(Context, OptionsParser->getCompilations(), PathList, BaseFS,
-                   FixNotes, EnableCheckProfile, ProfilePrefix);
+                   FixNotes, EnableCheckProfile, ProfilePrefix, Quiet);
   bool FoundErrors = llvm::any_of(Errors, [](const ClangTidyError &E) {
     return E.DiagLevel == ClangTidyError::Error;
   });

clang-tools-extra/docs/ReleaseNotes.rst

@@ -119,6 +119,9 @@ Improvements to clang-tidy
 - Improved documentation of the `-line-filter` command-line flag of
   :program:`clang-tidy` and :program:`run-clang-tidy.py`.
 
+- Improved :program:`clang-tidy` option `-quiet` by suppressing diagnostic
+  count messages.
+
 New checks
 ^^^^^^^^^^
 

clang-tools-extra/test/clang-tidy/infrastructure/file-filter-symlinks.cpp

@@ -10,7 +10,7 @@
 // RUN: clang-tidy -checks='-*,google-explicit-constructor' -header-filter='header_alias\.h' %s -- -I %t 2>&1 | FileCheck --check-prefix=CHECK_HEADER_ALIAS %s
 // RUN: clang-tidy -checks='-*,google-explicit-constructor' -header-filter='header_alias\.h' -quiet %s -- -I %t 2>&1 | FileCheck --check-prefix=CHECK_HEADER_ALIAS %s
 // RUN: clang-tidy -checks='-*,google-explicit-constructor' -header-filter='header\.h' %s -- -I %t 2>&1 | FileCheck --check-prefix=CHECK_HEADER %s
-// RUN: clang-tidy -checks='-*,google-explicit-constructor' -header-filter='header\.h' -quiet %s -- -I %t 2>&1 | FileCheck --check-prefix=CHECK_HEADER %s
+// RUN: clang-tidy -checks='-*,google-explicit-constructor' -header-filter='header\.h' -quiet %s -- -I %t 2>&1 | FileCheck --check-prefix=CHECK_HEADER --allow-empty %s
 
 // Check that `-header-filter` operates on the same file paths as paths in
 // diagnostics printed by ClangTidy.

clang-tools-extra/test/clang-tidy/infrastructure/quiet-flag.cpp

@@ -0,0 +1,26 @@
+// This test ensures that the --quiet flag only suppresses the "X warnings generated" 
+// message while keeping all diagnostic information including caret indicators (^).
+
+// RUN: clang-tidy -checks=-*,readability-magic-numbers,clang-diagnostic-sign-compare %s -- \
+// RUN:   -Wsign-compare 2>&1 | FileCheck %s --check-prefix=CHECK-NORMAL
+// RUN: clang-tidy -checks=-*,readability-magic-numbers,clang-diagnostic-sign-compare -quiet %s -- \
+// RUN:   -Wsign-compare 2>&1 | FileCheck %s --check-prefix=CHECK-QUIET
+
+// CHECK-NORMAL: 2 warnings generated
+// CHECK-NORMAL-DAG: warning: 42 is a magic number
+// CHECK-NORMAL-DAG: {{[ ]*\^}}
+// CHECK-NORMAL-DAG: warning: comparison of integers of different signs
+// CHECK-NORMAL-DAG: {{[ ]*~ \^ ~}}
+
+// CHECK-QUIET-NOT: {{[0-9]+}} warning{{s?}} generated
+// CHECK-QUIET-DAG: warning: 42 is a magic number
+// CHECK-QUIET-DAG: {{[ ]*\^}}
+// CHECK-QUIET-DAG: warning: comparison of integers of different signs
+// CHECK-QUIET-DAG: {{[ ]*~ \^ ~}}
+
+int main() {
+  const int CONST_VAL = 10;
+  int x = 42; // trigger 'readability-magic-numbers' with caret: ^
+  unsigned int y = CONST_VAL;
+  return x < y; // trigger 'clang-diagnostic-sign-compare' with caret: ^
+}