Zli - A friendly fork of TigerBeetle's flag module

ilx · May 11, 2024, 11:33am

Hey everyone!

Over the last couple of weeks I have been learning Zig and loving the experience so far!

In one of my side / learning projects I had the need for a CLI arg parser. At the time, I was browsing through TigerBeetle’s codebase to get a feel for how comptime is being used when I stumbled upon their flags.zig module.

The interface the authors created for that library was a design I really liked, and the general guidelines for CLI parsing were very similar to my own preferences and, except for a few features, suited my use case well for this side project.

I forked much of that code, refactored a little and added in support for subcommand specific help and short options.

I thought, on the off chance that others like the original interface but were missing those features, that I would share the repo here:

matklad · May 11, 2024, 8:17pm

Heads up, parsing of (multiple) positional arguments was broken completely as of yesterday, be sure to incude this change as well:

Another curious thing about original flags is testing. I giggle every time I see

github.com

tigerbeetle/tigerbeetle/blob/e408a477d3bc02644beee0ed33ac462f968228bf/src/flags.zig#L563


      
                  @as(*const field.type, @ptrCast(@alignCast(default_opaque))).*
              else
                  null;
          }
          
          // CLI parsing makes a liberal use of `fatal`, so testing it within the process is impossible. We
          // test it out of process by:
          //   - using Zig compiler to build this very file as an executable in a temporary directory,
          //   - running the following main with various args and capturing stdout, stderr, and the exit code.
          //   - asserting that the captured values are correct.
          pub usingnamespace if (@import("root") != @This()) struct {
              // For production builds, don't include the main function.
              // This is `if __name__ == "__main__":` at comptime!
          } else struct {
              const CliArgs = union(enum) {
                  empty,
                  prefix: struct {
                      foo: u8 = 0,
                      foo_bar: u8 = 0,
                      opt: bool = false,
                      option: bool = false,

Thanks for taking care of publishing it as a separate library! This is exactly our goal at TigerBeetle: while we want to stay focused on our specific requirements and don’t want to get distracted building reusable libraries (which is a hard job), our code is there to get copied, re-used and remixed!

ilx · May 11, 2024, 11:08pm

Thank you for taking the time to reply and for the kind alert regarding the positional fields.

During testing I did come across that issue - I implemented a fix for it here and had actually planned on opening a PR against the original source today! I was too late, it seems, haha.

I really do appreciate just how awesome the Zig community is and am very impressed with all the work that is going on at TigerBeetle! Reading through just a small amount of the source and the guidelines in Tiger Style has been an immensely helpful