[llvm] [Support]Look up in top-level subcommand as a fallback when looking options for a custom subcommand. (PR #71776)

[Snehasish Kumar via llvm-commits]

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@@ -525,6 +525,74 @@ TEST(CommandLineTest, LookupFailsInWrongSubCommand) {
   EXPECT_FALSE(Errs.empty());
 }
 
+TEST(CommandLineTest, SubcommandOptions) {
+  enum LiteralOptionEnum {
+    foo,
+    bar,
+    baz,
+  };
+
+  cl::ResetCommandLineParser();
+
+  // This is a top-level option and not associated with a subcommand.
+  // A command line using subcommand should parse both subcommand options and
+  // top-level options.  A valid use case is that users of llvm command line
+  // tools should be able to specify top-level options defined in any library.
+  cl::opt<std::string> TopLevelOpt("str", cl::init("txt"),
+                                   cl::desc("A top-level option."));
+
+  StackSubCommand SC("sc", "Subcommand");
+
+  // The positional argument.
+  StackOption<std::string> PositionalOpt(
+      cl::Positional, cl::desc("positional argument test coverage"),
+      cl::sub(SC));
+  // Thel literal argument.
+  StackOption<LiteralOptionEnum> LiteralOpt(
+      cl::desc("literal argument test coverage"), cl::sub(SC), cl::init(bar),
+      cl::values(clEnumVal(foo, "foo"), clEnumVal(bar, "bar"),
+                 clEnumVal(baz, "baz")));
+  StackOption<bool> BoolOpt("enable", cl::sub(SC), cl::init(false));
+
+  std::string Errs;
+  raw_string_ostream OS(Errs);
+
+  for (const char *literalArg : {"--bar", "--foo", "--baz"}) {
+    const char *args[] = {"prog",     "sc",      "input-file",
+                          literalArg, "-enable", "--str=csv"};
+
+    // cl::ParseCommandLineOptions returns true on success. it returns false
+    // and prints errors to caller provided error stream (&OS in this setting).
+    EXPECT_TRUE(cl::ParseCommandLineOptions(6, args, StringRef(), &OS));
----------------
snehasish wrote:

nit: sizeof(args) instead of 6

https://github.com/llvm/llvm-project/pull/71776