Can I use a transaction function to check invariants?

[Vaelatern]

Rather than using a transaction function to take an action, can I use one like so...

submitted-tx (crux/submit-tx @node [[:crux.tx/fn ::user-exists who]
                                    [:crux.tx/put object-body]])

Right now this fails to commit every time. The ::user-exists function returns either an empty vector or false. I've also tried returning a vector with an empty vector.

EDIT:

I may also be misunderstanding these in general. The following always ends with a false value.

(crux/submit-tx @node
                [[:crux.tx/put {:crux.db/id :TESTING-FN
                                :crux.db/fn '(fn [ctx]
                                                [[:crux.tx/put {:crux.tx/id :abc
                                                                :value :abc}]])}]])
(= nil (crux/entity (crux/db @node) :abc)) ;; true
(let [a (crux/submit-tx @node [[:crux.tx/fn :TESTING-FN]])]
  (crux/await-tx @node a)
  (crux/tx-committed? @node a)) ;; value: false

[refset]

Hi @Vaelatern - I believe everything works as expected if you change :crux.tx/id -> :crux.db/id :)

We could probably adapt the default logging to make transaction function errors more transparent during development - sorry it wasn't easier for you to spot this one!

[Vaelatern]

Alright, that solves the bottom case where I was misunderstanding, but unfortunately does not explain whether I can do nothing in a tx-fn and still end up OK.

[Vaelatern]

(crux/submit-tx @node
                [[:crux.tx/put {:crux.db/id :TESTING-FN
                                :crux.db/fn '(fn [ctx]
                                                [[:crux.tx/put {:crux.db/id :abc
                                                                :value :abc}]])}]])
(= nil (crux/entity (crux/db @node) :abc)) ;; true
(let [a (crux/submit-tx @node [[:crux.tx/fn :TESTING-FN]])]
  (crux/await-tx @node a)
  (crux/tx-committed? @node a)) ;; value: true

[refset]

Ah yes, it always helps to read the actual question before hitting reply...

You should be able to return false from the transaction function to abort the entire transaction. See this test: https://github.com/juxt/crux/blob/a736e0315c80d4bb5ad2857aaf9c5163451e89ec/crux-test/test/crux/tx_test.clj#L749-L769

It might be possible that the use of current-namespaced keyword ::user-exists for that invocation operation is confusing things.

[Vaelatern]

So returning false works, can I return true as a noop?

Testing suggests I can get what I want if I return [] on successfully matching the invariant, and false on failure.

[refset]

Yep, [] is the way to do it :)

Returning true would not be valid.