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.
  • Asetru@feddit.org
    21·
    5 months 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

      • Asetru@feddit.org
        1·
        5 months ago

        The result type in rust does not return a true/false but a type. More importantly though, it doesn’t return err if both values are set but simply returns the first value:

        So… It’s not only not mapping your input to truth values, it also behaves more like I’d expect an “or” to behave, which is not “xor” or, if there’s more than two inputs, “exactly one”, but succeeding if any input is set.

          • Asetru@feddit.org
            1·
            5 months ago

            Absolutely not.

            Mutually exclusive options

            Another classic. Pick one output format: JSON, YAML, or XML. But definitely not two.

            Emphasis mine.

            It takes the input and fails if there is more than one valid one, which decidedly isn’t what’s an “or” in comp sci.

  • azertyfun@sh.itjust.works
    20·
    5 months 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.

  • Serinus@lemmy.world
    6·
    5 months 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.