This is a BREAKING change to get in before v1 final.
Signal keys BEFORE this commit:
`:location` ---- ?{:keys [ns file line column]} signal creator callsite
`:ns` ---------- ?str namespace of signal creator callsite, same as (:ns location)
`:line` -------- ?int line of signal creator callsite, same as (:line location)
`:column` ------ ?int column of signal creator callsite, same as (:column location)
`:file` -------- ?str filename of signal creator callsite, same as (:file location)
Signal keys AFTER this commit:
`:ns` ---------- ?str namespace of signal creator callsite
`:coords` ------ ?[line column] of signal creator callsite
Motivation for the breaking change:
The new callsite schema is simpler to use/override, reduces noise, and can reduce
code expansion size (and so Cljs build size).
- `:file` was rarely useful, but often added large embedded strings.
- `:location` was redundant, and often difficult for Closure's
advanced build to properly de-duplicate.
This schema will be shared by Truss v2 and Tufte v3.
The improved performance rarely matters in practice, and can
cause issues for folks using deep-walking macros.
Better solution would be to eventually get the optimisation
implemented upstream in Clojure core.
