This is actually great, and I predict that fans of nil-punning will rapidly discover the joys of actually having errors trigger where the error was introduced rather than propagating through the program.
> Clojure’s idiomatic use of maps has proven valuable, but missing required keys, misspelled keys, and invalid values can lead to failures that do not connect to the actual source of the problem (e.g. NPEs) making diagnosis difficult. At the same time, Clojure lacks a simple inline mechanism for functions to document and check the keys they require and accept. Existing tools either separate those expectations from the function itself or couple data shape and data provision.
This is a case I never really thought about - if the key is missing today you'll get nil as the value and since Clojure is a nil punning language it usually does sensible behaviour in your program
I know this sounds unreliable but in practise I like a language that defaults to pragmatic code paths so I don't have to stay up at night imagining a million code paths
This adds a throwing codepath which is quite drastic so I'm glad people don't build this into programs everywhere - I'd be nice to hear what the team imagine as the use case for this
Normally for correctness I'd like to see specs at the boundaries for programs and different test suites for internal behaviours
The maps are still open to new keys even if some keys are checked. I think that fits in with how clojure.spec and Malli work already, but in a lighter syntax.
This is actually great, and I predict that fans of nil-punning will rapidly discover the joys of actually having errors trigger where the error was introduced rather than propagating through the program.
Any news on ClojureScript gaining the feature?
Some explanations from https://clojure.atlassian.net/browse/CLJ-2961:
> Clojure’s idiomatic use of maps has proven valuable, but missing required keys, misspelled keys, and invalid values can lead to failures that do not connect to the actual source of the problem (e.g. NPEs) making diagnosis difficult. At the same time, Clojure lacks a simple inline mechanism for functions to document and check the keys they require and accept. Existing tools either separate those expectations from the function itself or couple data shape and data provision.
This is a case I never really thought about - if the key is missing today you'll get nil as the value and since Clojure is a nil punning language it usually does sensible behaviour in your program
I know this sounds unreliable but in practise I like a language that defaults to pragmatic code paths so I don't have to stay up at night imagining a million code paths
This adds a throwing codepath which is quite drastic so I'm glad people don't build this into programs everywhere - I'd be nice to hear what the team imagine as the use case for this
Normally for correctness I'd like to see specs at the boundaries for programs and different test suites for internal behaviours
Is it only me or this sounds a bit counter to clojure philosophy?
The maps are still open to new keys even if some keys are checked. I think that fits in with how clojure.spec and Malli work already, but in a lighter syntax.
It's 100% opt-in at the call site and doesn't affect existing code, so no?
Many people (including myself) already have checked key variants for maps; this mainly extends the syntax to destructuring too.