Clojure

• Type: Feature
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: Release 1.9
• Fix Version/s: None
• Component/s: None
• Labels:

  None
• Environment:

  [org.clojure/spec.alpha "0.1.134"]

Problem

To do runtime coercion, specs need to be walked twice to strip away the branching information: s/conform + s/unform. This introduced extra latency (see the sample below).

Proposal

New versatile s/walk* to support generic spec walking.

Current status

• s/valid? allows us to do quickly check if a value conforms to a spec
  • https://dev.clojure.org/jira/browse/CLJ-2115 could help to return the errors in a single sweep.
• for coercion, we do s/conform + s/unform / s/explain
  • https://dev.clojure.org/jira/browse/CLJ-2116 would separate conforming from specs

Still, when running s/conform + s/unform, we walk the specs twice - which is performance-wise suboptimal. Below is a sample, with Late 2013 MacBook Pro with 2,5 GHz i7, with JVM running as -server.

(require '[clojure.spec.alpha :as s])

(s/def ::id int?)
(s/def ::name string?)
(s/def ::languages (s/coll-of #{:clj :cljs} :into #{}))
(s/def ::street string?)
(s/def ::zip string?)
(s/def ::number int?)

(s/def ::address (s/keys
                   :req-un [::street ::zip ::number]))

(s/def ::user (s/keys
                :req [::id]
                :req-un [::name ::address]
                :opt-un [::languages]))

(def value {::id 1
            :name "Liisa"
            :languages #{:clj :cljs}
            :address {:street "Hämeenkatu"
                      :number 24
                      :zip "33200"}})

; 2.0 µs
(cc/quick-bench
  (s/conform ::user value))

; 6.2 µs
(cc/quick-bench
  (s/unform ::user (s/conform ::user value)))

Despite s/conform is relatively fast, we triple the latency in the sample when running also s/unform. As we know already that we are not interested in the branching info, we could just not emit those.

Suggestion

s/walk* to replace both s/confrom* and s/unform*, maybe even s/explain*. It would take extra mode argument, which would be a Keyword of one of the following:

• :validate - return false on first failing spec
• :conform - like the current s/conform*, maybe also return s/explain results?
• :unform - like the current s/unform*
• :coerce - s/conform* + s/unform*, could be optimized (e.g. if no branching info, just return the value)

The public apis could be remain the same (+ optional extra argument with CLJ-2116), and a new s/coerce to call the s/walk* with :coerce.

Results

Single sweep validation & coercion. Happy runtime.

• Assignee:

  Unassigned

  Reporter:

  Tommi Reiman

• Created:

  11/Oct/17 1:22 PM

  Updated:

  27/Nov/18 12:02 PM