[Bug]: pull: attr-option doesn't work inside map-spec

[KsVlad]

What version of Datahike are you using?

0.6.1521

What version of Java are you using?

openjdk version "19.0.1" 2022-10-18

What operating system are you using?

Arch WSL (Windows 11)

What database EDN configuration are you using?

{:store {:backend :mem}}

Describe the bug

In pull pattern attr-option (:as, :limit) works:

(pull (db conn) '[(:attr :as "attr")] id)

but attr-option in map-spec throws with Expected (attr-name | limit-expr):

(pull (db conn) '[{(:attr :as "attr") [*]}] id)

See example in "How can the behaviour be reproduced?"

N.B. legacy-limit-expr in terms of Datomic works (e.g. (pull (db conn) '[{(limit :attr 1) [*]}] id)), so it's clear what exception is talking about.

What is the expected behaviour?

(pull (db conn) '[{(:attr :as "attr") [*]}] id)

Returns result with :attr substituted with "attr"

How can the behaviour be reproduced?

(def cfg {:store {:backend :mem}})
(def conn (d/connect cfg))

For schema:

(def schema [{:db/ident :name
              :db/valueType :db.type/string
              :db/cardinality :db.cardinality/one
              :db/unique :db.unique/identity}
             {:db/ident :friend
              :db/valueType :db.type/ref
              :db/cardinality :db.cardinality/one}])
(d/transact conn schema)

And seed data:

(d/transact conn [{:db/id -1
                   :name "Joe"}
                  {:name "Jane"
                   :friend -1}])

This pull works:

(d/pull (d/db conn) '[(:friend :as "body")] [:name "Jane"])
=> {"body" #:db{:id 3}}

This one doesn't:

(d/pull (d/db conn) '[{(:friend :as "body") [*]}] [:name "Jane"])
=> 
; Execution error (ExceptionInfo) at datalog.parser.pull/parse-map-spec-entry (pull.cljc:117).
; Expected (attr-name | limit-expr)

(Both works in Datomic dev-local)

[jsmassa]

Thank you for reporting this :)

It looks like our parser is not up-to-date with the Datomic pull grammar.
I can see this also has already been reported in replikativ/datalog-parser#25.

We should be able to fix this soon.

[KsVlad]

Also, have discovered only now, default-expr is not supported in simple attr-expr

(d/pull (d/db conn) '[(:misssing :default "default")] [:name "Jane"])
>
; Execution error (ExceptionInfo) at datahike.db.utils/validate-attr-ident (utils.cljc:157).
; Bad entity attribute :misssing at (resolve-datom db 4 :misssing nil nil), not defined in current schema

Seems like a different kind of error.

Please tell, is it worth a separate issue? Or maybe it is somewhat intended difference from datomic

[KsVlad]

Parser knows about :default

(d/pull (d/db conn) '[(:friend :default "default")] [:name "Jane"])
>
{:friend #:db{:id 3}}

But seems like a strange feature to have for only present on entity attributes :)

[KsVlad]

Oops, my bad
Bad entity attribute :misssing at (resolve-datom db 4 :misssing nil nil), **not defined in current schema**

I will read messages properly. With :misssing property defined everything works fine.

Anyway, assuming the label "datomic compat", some validity of question remain, because in datomic :defaults works even on properties not in the schema.

Now I'm stop spamming here. Please, let me know if there is a need to make a proper issue for :default thing.

[jsmassa]

Allowing :default values also on attributes not in the schema is indeed a separate issue that should be discussed.

We usually try to stay compatible with Datomic, so I guess we will want to support that sooner or later, but to me it seems like a strange feature to have, so that wouldn't be exactly a priority.

[jsmassa]

Btw, replikativ/datalog-parser#27 will update the parser and as soon as this is included in datahike the options should work like in datomic again.

[KsVlad]

We usually try to stay compatible with Datomic, so I guess we will want to support that sooner or later, but to me it seems like a strange feature to have, so that wouldn't be exactly a priority.

Agree with "strange" here. Throw in the face if I misspell some attribute seems like more preferable behavior to me.
It turned out It's more than :default. Datomic pull silently omits :not-in-schema on simple (pull db [:not-in-schema] id)

So, here is an #579 . A good candidate for wontfix it is, but let it be for future reference :)