dart-lang
Changes to Equality classes.
PROOF-OF-CONCEPT. DO NOT LAND.
MapEquality and SetEquality now expects the provided equalities to be compatible with the inherent equals (and hash) of the map or set.
That allows using Map.operator[] and Set.lookup to match entries/elements from one collection with those of the other, instead of building an extra
hash-map on the side to count occurrences.
This helps DeepCollectionEquality which is likely to traverse a larger collection structure (mainly maps) and do repeated equals/hash code on sup-components.
For unordered DeepCollectionEquality, a cache of computed values is added to avoid repeating the same computation during the traversal of a map-structure.
Smaller changes to other classes: DefaultEquality and IdentityEquality now have only factory constructors, so cannot be extended. There should be no need for that.
Also adds JsonEquality which is tuned to JSON-like map/list/basic-value structures, and which assumes everything uses default == equality.
NOTICE: This is probably a breaking change, so the version number should be major-version-incremented. I believe this package is pinned by Flutter, so that'll be fun. :wink:
