Exit with error when no checks enabled.

Summary:
This seems like a more appropriate reaction to the user specifying a
single check with a wrong name, for example.

Reviewers: klimek

Reviewed By: klimek

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3981

llvm-svn: 210043

1 files changed, 9 insertions, 1 deletions

diff --git a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
index 41b66d66a64..f338805fcfd 100644
--- a/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
+++ b/clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp
@@ -119,15 +119,23 @@ int main(int argc, const char **argv) {
     return 1;
   }
 
+  std::vector<std::string> EnabledChecks = clang::tidy::getCheckNames(Options);
+
   // FIXME: Allow using --list-checks without positional arguments.
   if (ListChecks) {
     llvm::outs() << "Enabled checks:";
-    for (auto CheckName : clang::tidy::getCheckNames(Options))
+    for (auto CheckName : EnabledChecks)
       llvm::outs() << "\n    " << CheckName;
     llvm::outs() << "\n\n";
     return 0;
   }
 
+  if (EnabledChecks.empty()) {
+    llvm::errs() << "Error: no checks enabled.\n";
+    llvm::cl::PrintHelpMessage(/*Hidden=*/false, /*Categorized=*/true);
+    return 1;
+  }
+
   std::vector<clang::tidy::ClangTidyError> Errors;
   clang::tidy::ClangTidyStats Stats =
       clang::tidy::runClangTidy(Options, OptionsParser.getCompilations(),