This post introduces Optique, a new library created to address the pervasive problem of repetitive and often messy validation code in CLI tools. The author was motivated by the observation that nearly every CLI tool reinvents the wheel with similar validation patterns for dependent options, mutually exclusive options, and environment-specific requirements. Optique leverages parser combinators and TypeScript's type inference to ensure that CLI arguments are parsed directly into valid configurations, eliminating the need for manual validation. By describing the desired CLI configuration with Optique, TypeScript automatically infers the types and constraints, catching potential bugs at compile time. The author shares their experience of deleting large chunks of validation code and simplifying refactoring tasks. Optique aims to provide a more robust and maintainable approach to CLI argument parsing, potentially saving developers from writing the same validation logic repeatedly.
  • azertyfun@sh.itjust.works
    14·
    11 hours ago

    Counterpoint: Yes, parse don’t validate, but CLIs should not be dealing with dependency management.

    I love Python’s argparse because:

    • It’s “Parse, don’t validate” (even supports FileType as a target)
    • It enforces or strongly encourages good CLI design
      • Required arguments should in most situations be positional arguments, not flags. It’s curl <URL> not curl --url <URL>.
      • Flags should not depend on each other. That usually indicates spaghetti CLI design. Don’t do server --serve --port 8080 and server --reload with rules for mix-and-matching those, do server serve --port 8080 and server reload with two separate subparsers.
      • Mutually exclusive flags sometimes make sense but usually don’t. Don’t do --xml --json, do -f [xml|json].
      • This or( pattern of yours IMO should always be replaced by a subparser (which can use inheritance!). As a user the options’ data model should be immediately intuitive to me as I look at the --help and having mutually exclusive flags forces the user to do the extra work of dependency management. Don’t do server --env prod --auth abc --ssl, do server serve prod --auth abc --ssl where prod is its own subparser inheriting from AbstractServeParser or whatever.

    Thinking of CLI flags as a direct mapping to runtime variables is the fundamental mistake here I think. A CLI should be a mapping to the set(s) of behavior(s) of your application. A good CLI may have mandatory positional arguments but has 0 mandatory flags, 0 mutually exclusive flags, and if it implements multiple separate behaviors should be a tree of subparsers. Any mandatory or mutually exclusive flags should be an immediate warning that you’re not being very UNIX-y in your CLI design.

    • Onno (VK6FLAB)@lemmy.radio
      1·
      8 hours ago

      I’ve used the node.js version of argparse, which as I understand it, is a clone of the python implementation and I’ve not seen how to do mutually exclusive flags. Mind you, at the time I didn’t need them, so it wasn’t an issue, but I don’t recall seeing any way to do it either.

      Did I miss something?

  • Asetru@feddit.org
    134·
    13 hours ago

    The or() combinator means exactly one succeeds.

    Using “or” to define a function that does “xor”… Did that guy never hear about formal logic? That’s, like, first or second semester stuff…

    Here’s the thing: I don’t have a CS degree.

    sigh

    • kibiz0r@midwest.socialEnglish
      61·
      20 hours ago

      Not exactly an answer, but I’ll take the opportunity to point out that Bun has a shell feature which makes it easy to mix and match JS and Bash in the same script, and it provides a compatibility layer for Windows users so that you don’t have to worry about platform differences in shell capabilities. https://bun.sh/guides/runtime/shell

  • Serinus@lemmy.world
    71·
    21 hours ago

    I’m not sure the value added is worth the extra layer.

    I guess my command line options just aren’t all that complicated.

  • TehPers@beehaw.orgEnglish
    3·
    1 day ago

    I like the concept, and it’s great in TS. Unfortunately, not as doable in other languages.

    I’m a bit curious if it’s possible to extend clap to do this in Rust though (specifically mutually-exclusive arg groups).

      • TehPers@beehaw.orgEnglish
        9·
        23 hours ago

        This doesn’t represent the mutual exclusivity through the type system (which is what the article is all about).

        I love clap and I use it a lot, but the only way to represent the exclusivity through the type system in Rust is through an enum.

        • ExFed@programming.dev
          5·
          22 hours ago

          Agreed. As nice as clap is, it’s not a combinator. Parser combinators have a the really nice feature of sharing the same “shape” as the data they parse, which makes them trivial to generate from a schema … or to just use them to represent your schema in the first place ;) .

      • TehPers@beehaw.orgEnglish
        6·
        23 hours ago

        Mentioned this to the other commenter, but this doesn’t use the type system to enforce the mutual exclusivity constraint. In Rust, the main way to do that via the type system is through enums.

        • Ephera@lemmy.mlEnglish
          3·
          17 hours ago

          Ah, fair enough. Not sure how to do that then.

          I was gonna say, I feel like the current method does a good enough job documenting that validation has happened, but I guess you do want it reflected in the structure of the type, so that the code that takes the information from the struct can safely make the assumption that some of the options don’t exist. And then, yeah, it would be nice to not need a separate parsing step for that.