[Support][CommandLine] Add cl::getRegisteredSubcommands()

This should allow users of the library to get a range to iterate through
all the subcommands that are registered to the global parser. This
allows users to define subcommands in libraries that self-register to
have dispatch done at a different stage (like main). It allows for
writing code like the following:

    for (auto *S : cl::getRegisteredSubcommands()) {
      if (*S) {
	// Dispatch on S->getName().
      }
    }

This change also contains tests that show this usage pattern.

Reviewers: zturner, dblaikie, echristo

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D24489

llvm-svn: 281290

llvm/include/llvm/Support/CommandLine.h

@@ -1736,6 +1736,28 @@ void PrintHelpMessage(bool Hidden = false, bool Categorized = false);
 /// than just handing around a global list.
 StringMap<Option *> &getRegisteredOptions(SubCommand &Sub = *TopLevelSubCommand);
 
+/// \brief Use this to get all registered SubCommands from the provided parser.
+///
+/// \return A range of all SubCommand pointers registered with the parser.
+///
+/// Typical usage:
+/// \code
+/// main(int argc, char* argv[]) {
+///   llvm::cl::ParseCommandLineOptions(argc, argv);
+///   for (auto* S : llvm::cl::getRegisteredSubcommands()) {
+///     if (*S) {
+///       std::cout << "Executing subcommand: " << S->getName() << std::endl;
+///       // Execute some function based on the name...
+///     }
+///   }
+/// }
+/// \endcode
+///
+/// This interface is useful for defining subcommands in libraries and
+/// the dispatch from a single point (like in the main function).
+iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
+getRegisteredSubcommands();
+
 //===----------------------------------------------------------------------===//
 // Standalone command line processing utilities.
 //

llvm/lib/Support/CommandLine.cpp

@@ -309,6 +309,12 @@ class CommandLineParser {
     RegisteredSubCommands.erase(sub);
   }
 
+  iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
+  getRegisteredSubcommands() {
+    return make_range(RegisteredSubCommands.begin(),
+                      RegisteredSubCommands.end());
+  }
+
   void reset() {
     ActiveSubCommand = nullptr;
     ProgramName.clear();
@@ -2105,6 +2111,11 @@ StringMap<Option *> &cl::getRegisteredOptions(SubCommand &Sub) {
   return Sub.OptionsMap;
 }
 
+iterator_range<typename SmallPtrSet<SubCommand *, 4>::iterator>
+cl::getRegisteredSubcommands() {
+  return GlobalParser->getRegisteredSubcommands();
+}
+
 void cl::HideUnrelatedOptions(cl::OptionCategory &Category, SubCommand &Sub) {
   for (auto &I : Sub.OptionsMap) {
     if (I.second->Category != &Category &&

llvm/unittests/Support/CommandLineTest.cpp

@@ -476,4 +476,27 @@ TEST(CommandLineTest, RemoveFromAllSubCommands) {
   EXPECT_FALSE(cl::ParseCommandLineOptions(3, args2, nullptr, true));
 }
 
+TEST(CommandLineTest, GetRegisteredSubcommands) {
+  cl::ResetCommandLineParser();
+
+  StackSubCommand SC1("sc1", "First Subcommand");
+  StackSubCommand SC2("sc2", "Second subcommand");
+
+  const char *args0[] = {"prog", "sc1"};
+  const char *args1[] = {"prog", "sc2"};
+
+  EXPECT_TRUE(cl::ParseCommandLineOptions(2, args0, nullptr, true));
+  for (auto *S : cl::getRegisteredSubcommands()) {
+    if (*S)
+      EXPECT_STREQ("sc1", S->getName());
+  }
+
+  cl::ResetAllOptionOccurrences();
+  EXPECT_TRUE(cl::ParseCommandLineOptions(2, args1, nullptr, true));
+  for (auto *S : cl::getRegisteredSubcommands()) {
+    if (*S)
+      EXPECT_STREQ("sc2", S->getName());
+  }
+}
+
 }  // anonymous namespace