[clang-tooling] Prevent llvm::fatal_error on invalid CLI option

[serge-sans-paille]

Summary

Fail gracefully instead. Prevent further misuse by enforcing the factory builder instead of the constructor.

[serge-sans-paille]

ping ? This change looks harmless to me, I'd appreciate an ack though.

[alexfh]

This is quite a bit of extra boilerplate, but it results in a more transparent error handling. However, the documentation would need to be changed (clang/docs/LibASTMatchersTutorial.rst). And what about other tools (e.g. clang-tools-extra/clang-include-fixer/tool/ClangIncludeFixer.cpp, clang-tools-extra/clang-include-fixer/find-all-symbols/tool/FindAllSymbolsMain.cpp, etc.)?

[serge-sans-paille]

Address doc + tool-extra issues

[serge-sans-paille]

Thanks @alexfh ! Should be good now.

[serge-sans-paille]

@alexfh gentle ping?

[alexfh]

Thanks! Looks good now.

[nridge]

It would be nice to update the code example in the LibTooling documentation as well

clang/include/clang/Tooling/CommonOptionsParser.h

 /// int main(int argc, const char **argv) {
 ///   CommonOptionsParser OptionsParser(argc, argv, MyToolCategory);
 ///   ClangTool Tool(OptionsParser.getCompilations(),
 ///                  OptionsParser.getSourcePathList());
 ///   return Tool.run(newFrontendActionFactory<SyntaxOnlyAction>().get());
 /// }
 /// \endcode
 class CommonOptionsParser {
-public:
-  /// Parses command-line, initializes a compilation database.
-  ///
-  /// This constructor can change argc and argv contents, e.g. consume
-  /// command-line options used for creating FixedCompilationDatabase.
-  ///
-  /// All options not belonging to \p Category become hidden.
-  ///
-  /// This constructor exits program in case of error.
-  CommonOptionsParser(int &argc, const char **argv,
-                      llvm::cl::OptionCategory &Category,
-                      const char *Overview = nullptr)
-      : CommonOptionsParser(argc, argv, Category, llvm::cl::OneOrMore,
-                            Overview) {}
 
+protected:
   /// Parses command-line, initializes a compilation database.
   ///
   /// This constructor can change argc and argv contents, e.g. consume
   /// command-line options used for creating FixedCompilationDatabase.
   ///
   /// All options not belonging to \p Category become hidden.
   ///
   /// It also allows calls to set the required number of positional parameters.
-  CommonOptionsParser(int &argc, const char **argv,
-                      llvm::cl::OptionCategory &Category,
-                      llvm::cl::NumOccurrencesFlag OccurrencesFlag,
-                      const char *Overview = nullptr);
+  CommonOptionsParser(
+      int &argc, const char **argv, llvm::cl::OptionCategory &Category,
+      llvm::cl::NumOccurrencesFlag OccurrencesFlag = llvm::cl::OneOrMore,
 
+public:
   /// A factory method that is similar to the above constructor, except
   /// this returns an error instead exiting the program on error.
   static llvm::Expected<CommonOptionsParser>
   create(int &argc, const char **argv, llvm::cl::OptionCategory &Category,
-         llvm::cl::NumOccurrencesFlag OccurrencesFlag,
+         llvm::cl::NumOccurrencesFlag OccurrencesFlag = llvm::cl::OneOrMore,
          const char *Overview = nullptr);
 
   /// Returns a reference to the loaded compilations database.
   CompilationDatabase &getCompilations() {
     return *Compilations;
   }
 
   /// Returns a list of source file paths to process.

clang/lib/Tooling/CommonOptionsParser.cpp

llvm::Error CommonOptionsParser::init(
   Compilations =
       FixedCompilationDatabase::loadFromCommandLine(argc, argv, ErrorMessage);
   if (!ErrorMessage.empty())
     ErrorMessage.append("\n");
   llvm::raw_string_ostream OS(ErrorMessage);
   // Stop initializing if command-line option parsing failed.
   if (!cl::ParseCommandLineOptions(argc, argv, Overview, &OS)) {
     OS.flush();
-    return llvm::make_error<llvm::StringError>("[CommonOptionsParser]: " +
-                                                   ErrorMessage,
+    return llvm::make_error<llvm::StringError>(ErrorMessage,
                                                llvm::inconvertibleErrorCode());
   }
 
   cl::PrintOptionValues();
 
   SourcePathList = SourcePaths;
   if ((OccurrencesFlag == cl::ZeroOrMore || OccurrencesFlag == cl::Optional) &&
       SourcePathList.empty())

clang/tools/clang-check/ClangCheck.cpp

int main(int argc, const char **argv) {
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
 
   // Initialize targets for clang module support.
   llvm::InitializeAllTargets();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllAsmPrinters();
   llvm::InitializeAllAsmParsers();
 
-  CommonOptionsParser OptionsParser(argc, argv, ClangCheckCategory);
+  auto ExpectedParser =
+      CommonOptionsParser::create(argc, argv, ClangCheckCategory);
+  if (!ExpectedParser) {
+    llvm::errs() << ExpectedParser.takeError();
+    return 1;
+  }
+  CommonOptionsParser &OptionsParser = ExpectedParser.get();
   ClangTool Tool(OptionsParser.getCompilations(),
                  OptionsParser.getSourcePathList());
 
   // Clear adjusters because -fsyntax-only is inserted by the default chain.
   Tool.clearArgumentsAdjusters();
   Tool.appendArgumentsAdjuster(getClangStripOutputAdjuster());
   Tool.appendArgumentsAdjuster(getClangStripDependencyFileAdjuster());
 

clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp

 int main(int argc, const char **argv) {
   // Print a stack trace if we signal out.
   sys::PrintStackTraceOnErrorSignal(argv[0], false);
   PrettyStackTraceProgram X(argc, argv);
 
   const char *Overview = "\nThis tool collects the USR name and location "
                          "of external definitions in the source files "
                          "(excluding headers).\n";
-  CommonOptionsParser OptionsParser(argc, argv, ClangExtDefMapGenCategory,
-                                    cl::ZeroOrMore, Overview);
+  auto ExpectedParser = CommonOptionsParser::create(
+      argc, argv, ClangExtDefMapGenCategory, cl::ZeroOrMore, Overview);
+  if (!ExpectedParser) {
+    llvm::errs() << ExpectedParser.takeError();
+    return 1;
+  }
+  CommonOptionsParser &OptionsParser = ExpectedParser.get();
 
   ClangTool Tool(OptionsParser.getCompilations(),
                  OptionsParser.getSourcePathList());
 
   return Tool.run(newFrontendActionFactory<MapExtDefNamesAction>().get());
 }

clang/tools/clang-refactor/ClangRefactor.cpp

 
 } // end anonymous namespace
 
 int main(int argc, const char **argv) {
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
 
   ClangRefactorTool RefactorTool;
 
-  CommonOptionsParser Options(
+  auto ExpectedParser = CommonOptionsParser::create(
       argc, argv, cl::GeneralCategory, cl::ZeroOrMore,
       "Clang-based refactoring tool for C, C++ and Objective-C");
+  if (!ExpectedParser) {
+    llvm::errs() << ExpectedParser.takeError();
+    return 1;
+  }
+  CommonOptionsParser &Options = ExpectedParser.get();
 
   if (auto Err = RefactorTool.Init()) {
     llvm::errs() << llvm::toString(std::move(Err)) << "\n";
     return 1;
   }
 
   auto ActionFactory = RefactorTool.getFrontendActionFactory();
   if (!ActionFactory) {

clang/tools/clang-rename/ClangRename.cpp

 static cl::opt<std::string>
     Input("input", cl::desc("YAML file to load oldname-newname pairs from."),
           cl::Optional, cl::cat(ClangRenameOptions));
 static cl::opt<bool> Force("force",
                            cl::desc("Ignore nonexistent qualified names."),
                            cl::cat(ClangRenameOptions));
 
 int main(int argc, const char **argv) {
-  tooling::CommonOptionsParser OP(argc, argv, ClangRenameOptions);
+  auto ExpectedParser =
+      tooling::CommonOptionsParser::create(argc, argv, ClangRenameOptions);
+  if (!ExpectedParser) {
+    llvm::errs() << ExpectedParser.takeError();
+    return 1;
+  }
+  tooling::CommonOptionsParser &OP = ExpectedParser.get();
 
   if (!Input.empty()) {
     // Populate QualifiedNames and NewNames from a YAML file.
     ErrorOr<std::unique_ptr<MemoryBuffer>> Buffer =
         llvm::MemoryBuffer::getFile(Input);
     if (!Buffer) {
       errs() << "clang-rename: failed to read " << Input << ": "
              << Buffer.getError().message() << "\n";