Provide a means to ask a spec for its "child" specs

Question

Some kinds of operations on specs are currently hard to implement as there is no uniform way to find what "child" specs are being composed by a spec. Examples:

* Dependency analysis
* Deep describe (show all specs used by a top-level spec)
* Detection of missing or invalid spec names

For example, given:


(s/def ::user-id int?)
(s/def ::user (s/keys :req [::userid])) ;; note misspelling
(s/valid? ::user {::userid "Jim"}) ;; => true but expect false


And the means to determine the "child" specs of ::user, a linter could check whether all of the keys in s/keys are specs that have been defined.

*Workarounds:*

1. {{form}} can be used to get the original spec form, but that must then be further interpreted (and is missing the original lexical environment in which it was created). Example attempt: https://gist.github.com/ericnormand/6cfe6809beeeea3246679e904372cca0
2. Spec form specs (CLJ-2112) are not available yet, but could be used to get a parsed representation of specs, which would still require some processing but would at least have known forms.

*Proposed:*

Add a mechanism to get the "child" specs a spec is composed of. Each spec implementation could then choose how to implement this in the appropriate way.

Answer 1

Comment made by: ericnormand

I forgot to add this proposal:

Proposal

I propose that we add a children* method to the Spec protocol. It should return a collection of specs directly referred to. The specs in the collection should be a keyword (if it is referred to by name), an instance of Spec (for nested specs), or some other value valid as a spec (such as a fn).

Answer 2

Comment made by: alexmiller

Rewrote title and some of the description to be less dependent on implementation details (which may change) and more about the problem at hand.

Answer 3

Reference: https://clojure.atlassian.net/browse/CLJ-2208 (reported by ericnormand)