[clang] [clang-tools-extra] [lld] [llvm] [llvm] Add subcommand support for OptTable (PR #155026)

[via llvm-commits]

================
@@ -0,0 +1,123 @@
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Option/OptTable.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+using namespace llvm::opt;
+
+namespace {
+enum ID {
+  OPT_INVALID = 0,
+#define OPTION(PREFIXES, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS,       \
+               VISIBILITY, PARAM, HELPTEXT, HELPTEXTSFORVARIANTS, METAVAR,     \
+               VALUES, COMMANDIDS_OFFSET)                                      \
+  OPT_##ID,
+#include "Opts.inc"
+#undef OPTION
+};
+#define OPTTABLE_STR_TABLE_CODE
+#include "Opts.inc"
+#undef OPTTABLE_STR_TABLE_CODE
+
+#define OPTTABLE_PREFIXES_TABLE_CODE
+#include "Opts.inc"
+#undef OPTTABLE_PREFIXES_TABLE_CODE
+
+#define OPTTABLE_COMMAND_IDS_TABLE_CODE
+#include "Opts.inc"
+#undef OPTTABLE_COMMAND_IDS_TABLE_CODE
+
+#define OPTTABLE_COMMANDS_CODE
+#include "Opts.inc"
+#undef OPTTABLE_COMMANDS_CODE
+
+static constexpr OptTable::Info InfoTable[] = {
+#define OPTION(...) LLVM_CONSTRUCT_OPT_INFO(__VA_ARGS__),
+#include "Opts.inc"
+#undef OPTION
+};
+
+class HelloSubOptTable : public GenericOptTable {
+public:
+  HelloSubOptTable()
+      : GenericOptTable(OptionStrTable, OptionPrefixesTable, InfoTable, false,
+                        OptionCommands, OptionCommandIDsTable) {}
+};
+} // namespace
+
+int main(int argc, char **argv) {
+  InitLLVM X(argc, argv);
+  HelloSubOptTable T;
+  unsigned MissingArgIndex, MissingArgCount;
+
+  auto HandleMultipleSubcommands = [](ArrayRef<StringRef> SubCommands) {
+    assert(SubCommands.size() > 1);
+    llvm::errs() << "error: more than one subcommand passed [\n";
+    for (auto SC : SubCommands)
+      llvm::errs() << " `" << SC << "`\n";
+    llvm::errs() << "]\n";
+    llvm::errs() << "See --help.\n";
+    exit(1);
+  };
+
+  auto HandleOtherPositionals = [](ArrayRef<StringRef> Positionals) {
+    assert(!Positionals.empty());
+    llvm::errs() << "error: unknown positional argument(s) [\n";
+    for (auto SC : Positionals)
+      llvm::errs() << " `" << SC << "`\n";
+    llvm::errs() << "]\n";
+    llvm::errs() << "See --help.\n";
+    exit(1);
+  };
+
+  InputArgList Args = T.ParseArgs(ArrayRef(argv + 1, argc - 1), MissingArgIndex,
+                                  MissingArgCount);
+
+  StringRef Subcommand = Args.getSubcommand(
+      T.getCommands(), HandleMultipleSubcommands, HandleOtherPositionals);
+  // Handle help. When help options is found, ignore all other options and exit
+  // after printing help.
+  if (Args.hasArg(OPT_help)) {
+    T.printHelp(llvm::outs(), "llvm-hello-sub [subcommand] [options]",
+                "LLVM Hello Subcommand Example", false, false, Visibility(),
+                Subcommand);
+    return 0;
+  }
+  bool HasUnknownOptions = false;
+  for (const Arg *A : Args.filtered(OPT_UNKNOWN)) {
+    HasUnknownOptions = true;
+    llvm::errs() << "Unknown option `" << A->getAsString(Args) << "'\n";
+  }
+  if (HasUnknownOptions) {
+    llvm::errs() << "See `OptSubcommand --help`.\n";
+    return 1;
+  }
+  if (Subcommand.empty()) {
+    if (Args.hasArg(OPT_version)) {
+      llvm::outs() << "LLVM Hello Subcommand Example 1.0\n";
+    }
----------------
PiJoules wrote:

https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

```
    if (Args.hasArg(OPT_version))
      llvm::outs() << "LLVM Hello Subcommand Example 1.0\n";
```

https://github.com/llvm/llvm-project/pull/155026