I've commented on this in multiple other places but for the sake of
completeness...
Datascript is extending some defrecords to the IHashEq protocol to add
custom hash caching. In particular, this extension is adding custom fields
__hash and __hasheq, which happen to be the (obvious) names of the new
fields added in alpha12 via CLJ-1224 to support built-in hashcode caching
(like maps).
Records are designed to hash like maps and to have hashing provided by the
language, not customized by the user. Due to this, and to the use of fields
with __-prefix, I consider the existing Datascript code to be invalid. I
have examined all uses of __hash fields and IHashEq on Github (many many
pages of results) and have found no other examples of this in tandem with
defrecord.
Note that deftype does NOT provide a hashing mechanism - deftypes are not
given map capabilities, hashing, or many of the things provided
automatically by defrecord. It is thus common, acceptable, and encouraged
for deftype users to provide a hashing strategy appropriate to the deftype.
My comments above apply only to defrecord, not to deftype.
Datascript should either remove these extensions or switch to using deftype
for these use cases.
On Wednesday, September 7, 2016 at 8:18:13 PM UTC-5, lvh wrote:
> CLJ-1224 appears to have broken Datascript, which now doesn’t compile:
>
> Exception in thread "main" java.lang.AssertionError: The names in #{__hash
> __meta __hasheq __extmap} cannot be used as field names for types or
> records., compiling:(datascript/db.cljc:369:1)
>
> The ticket mentions CLJS compat; it looks like it only adds __hash in CLJ:
>
>
> https://github.com/tonsky/datascript/blob/0684c4102706bf4ee8b2496ad35c32ced08640fc/src/datascript/db.cljc
>
> Not sure what the ideal way to solve this is…
>
>
> lvh
>
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