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

[Fangrui Song via llvm-commits]

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@@ -525,6 +525,58 @@ 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.
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MaskRay wrote:

The code self explains. I think the comments are unneeded.

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