Make NumOccurrenceFlag for SourcePaths configurable

[hintonda]

Summary

Added an additional ctor that takes a NumOccurrenceFlag parameter for the
SourcePaths option. This frees applications from always having to pass at least
one source file, e.g., -list-checks.

[alexfh]

Looks good with a few nits. I'll fix them and submit the patch for you. Thanks for fixing this!

include/clang/Tooling/CommonOptionsParser.h

76

nit: There should be no space before the parenthesis. Also, the 80-column limit seems to be exceeded.

90

No need for enum.

lib/Tooling/CommonOptionsParser.cpp

97

nit: No need for enum, column limit.

124

OccurrencesFlag can potentially be set to Optional, which should be handled in some way as well.

[alexfh]

Fixed the issues and committed revision 245204.

Thank you!

[hintonda]

Great, thanks again...

include/clang/Tooling/CommonOptionsParser.h

public:
   /// 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) {}
+
+  /// \brief 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.
+  ///
+  /// I also allows calls to set the required number of positional parameters.
+  ///
+  /// This constructor exits program in case of error.
+  CommonOptionsParser(int &argc, const char **argv,
+                      llvm::cl::OptionCategory &Category,
+                      enum llvm::cl::NumOccurrencesFlag OccurrencesFlag,
                       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.

lib/Tooling/CommonOptionsParser.cpp

for (CompileCommand &Command : Commands)
         Command.CommandLine = Adjuster(Command.CommandLine);
     return Commands;
   }
 };
 } // namespace
 
 CommonOptionsParser::CommonOptionsParser(int &argc, const char **argv,
                                          cl::OptionCategory &Category,
+                                         enum llvm::cl::NumOccurrencesFlag OccurrencesFlag,
                                          const char *Overview) {
   static cl::opt<bool> Help("h", cl::desc("Alias for -help"), cl::Hidden);
 
   static cl::opt<std::string> BuildPath("p", cl::desc("Build path"),
                                         cl::Optional, cl::cat(Category));
 
   static cl::list<std::string> SourcePaths(
-      cl::Positional, cl::desc("<source0> [... <sourceN>]"), cl::OneOrMore,
+      cl::Positional, cl::desc("<source0> [... <sourceN>]"), OccurrencesFlag,
       cl::cat(Category));
 
   static cl::list<std::string> ArgsAfter(
       "extra-arg",
       cl::desc("Additional argument to append to the compiler command line"),
       cl::cat(Category));
 
   static cl::list<std::string> ArgsBefore(
       "extra-arg-before",
       cl::desc("Additional argument to prepend to the compiler command line"),
       cl::cat(Category));
 
   cl::HideUnrelatedOptions(Category);
 
   Compilations.reset(FixedCompilationDatabase::loadFromCommandLine(argc,
                                                                    argv));
   cl::ParseCommandLineOptions(argc, argv, Overview);
   SourcePathList = SourcePaths;
+  if (OccurrencesFlag == cl::ZeroOrMore && SourcePathList.empty())
+    return;
   if (!Compilations) {
     std::string ErrorMessage;
     if (!BuildPath.empty()) {
       Compilations =
           CompilationDatabase::autoDetectFromDirectory(BuildPath, ErrorMessage);
     } else {
       Compilations = CompilationDatabase::autoDetectFromSource(SourcePaths[0],
                                                                ErrorMessage);