Transaction / Indexing bug

Start by running the reproduction with d/db-with, d/touch, and the :aevt index shown in the issue. Trace how a map containing :foo/relations and reverse refs is processed during the transaction. Done means db-with-foo-backwards retains foo3 and its relation datoms, and touching the related entities no longer asserts on entity?.

In a transaction where a map has refs and reverse-ref attributes, the ref attributes are thrown away.

This works:

(require '[datascript.core :as d])

(def db
  (d/empty-db
    {:foo/id        {:db/unique :db.unique/identity}
     :foo/relations {:db/valueType   :db.type/ref
                     :db/cardinality :db.cardinality/many}}))

(def db-with-foo
  (d/db-with
    db
    [{:foo/id        "foo1"
      :foo/relations [{:foo/id "foo2"}
                      {:foo/id "foo3"}]}]))

(comment
 (d/touch (d/entity db-with-foo [:foo/id "foo3"]))
; works!
; => {:foo/id "foo3", :db/id 3}
)

This fails for :foo/relations [{:foo/id "foo3"}] but works for the reverse :foo/_relations:

(def db-with-foo-backwards
  (d/db-with
    db
    [{:foo/id         "foo2"
      :foo/_relations [{:foo/id "foo1" :foo/relations [{:foo/id "foo3"}]}]}]))

(comment
 (d/touch (d/entity db-with-foo-backwards [:foo/id "foo3"]))
; errors!
; => #object[Error Error: Assert failed: (entity? e)] 

; relation between "foo1" and "foo2" exists
(d/touch (d/entity db-with-foo-backwards [:foo/id "foo1"])) 
 ; => {:foo/id "foo1", :foo/relations #{#:db{:id 1}}, :db/id 2}
)

Looking at the indexes of either DB we see that the relations and datoms are missing in db-with-foo-backwards:

(comment
 (:aevt db-with-foo)
; =>
;#{#datascript/Datom[1 :foo/id "foo1" 536870913 true]
;  #datascript/Datom[2 :foo/id "foo2" 536870913 true]
;  #datascript/Datom[3 :foo/id "foo3" 536870913 true] ; <-- foo3 exists!
;  #datascript/Datom[1 :foo/relations 2 536870913 true]
;  #datascript/Datom[1 :foo/relations 3 536870913 true]}
)
(comment
  (:aevt db-with-foo-backwards)
; =>
;#{#datascript/Datom[1 :foo/id "foo2" 536870913 true]
;  #datascript/Datom[2 :foo/id "foo1" 536870913 true] ; <-- foo3 and relations missing!
;  #datascript/Datom[2 :foo/relations 1 536870913 true]}
)