->/->> drop-in replacements that detailedly report errors

[vemv]

Create a ->/->>/some->/some->> replacement such that if any member of the chain fails, all previous members' (inclusive) arguments and return values are printlned.

This would greatly improve the debuggability of Clojure programs, and foster usage of threading macros, which are superior to call chains for a number of reasons.

Example:

• Given (-> x f1 (f2 some-arg) f3)
• If f2 throws an error
• The following is printed:

The (-> x f1 (f2 some-arg) f3) chain failed at f2.

f1 execution:

  Input:

    {:a 2}

  Output:

    {:a 3000}

f2 execution:

  Input:

    {:a 3000},
    ::some-argument

  Exception:

   FooBarException

The implementation should observe clojure.core/*assert*:

• if true, do as above
• else, expand to clojure.core/->
  • i.e. zero-cost abstraction

Considerations

• Should be a .cljc library, since .cljs compat as an afterthought can be harder
• printlned values should have a limit
  • huge vals can degrade IDE/term performance
  • particularly true for infinite seqs
    • maybe some heuristic for detection is possible
• Perhaps some 'rate-limiting' is necessary
  • e.g. one println should happen at most for a given 10s window
  • else, exceptions triggered (and caught) within loops might cause repetitive output
• println should be the default "print function", but there should be a configurable print-function
  • e.g. (alter-var-root #'the/print-fn (constantly timbre/debug))

[vemv]

Some prior art exists, but personally I don't find those -> replacements as elegant.

This one would be truly drop-in and zero-cost, with nothing new for users to learn.