Using `exists()` in policy with syntax error produces very obtuse stack trace

[olivermt]

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Versions

main

Operating system

All

Current Behavior

Broken syntax inside exists() like for example:

exists(foo.bar == "bar") as opposed to correct syntax exists(foo, bar == "bar") gives an obtuse stack trace that gives no information about whats wrong:

** (Ash.Error.Unknown) 
Bread Crumbs:
  > Exception raised in: Safari.Outcrop.PaleoMap.read
  > Exception raised in: Safari.Outcrop.Outcrop.read

Unknown Error

* ** (ArgumentError) `nil` is not a Spark DSL module.

  nil.persisted(:data_layer)
  (spark 2.2.67) lib/spark/dsl/extension.ex:138: Spark.Dsl.Extension.persisted!/3
  (ash 3.5.25) lib/ash/filter/filter.ex:3881: Ash.Filter.do_hydrate_refs/2
  (ash 3.5.25) lib/ash/filter/filter.ex:3763: Ash.Filter.do_hydrate_refs/2
  (safari 0.1.0) lib/safari/policy/end_user_read_access.ex:2: Safari.Policy.EndUserReadAccess.try_strict_check/3
  (ash 3.5.25) lib/ash/policy/policy.ex:183: Ash.Policy.Policy.fetch_or_strict_check_fact/2
  (ash 3.5.25) lib/ash/policy/policy.ex:427: Ash.Policy.Policy.handle_constants/2
  (ash 3.5.25) lib/ash/policy/policy.ex:390: Ash.Policy.Policy.handle_constants/2
  (ash 3.5.25) lib/ash/policy/policy.ex:402: Ash.Policy.Policy.handle_constants/2
  (ash 3.5.25) lib/ash/policy/policy.ex:390: Ash.Policy.Policy.handle_constants/2
  (ash 3.5.25) lib/ash/policy/policy.ex:29: Ash.Policy.Policy.solve/1
  (ash 3.5.25) lib/ash/policy/checker.ex:65: Ash.Policy.Checker.strict_check_scenarios/1
  (ash 3.5.25) lib/ash/policy/authorizer/authorizer.ex:1724: Ash.Policy.Authorizer.strict_check_result/2
  (ash 3.5.25) lib/ash/policy/authorizer/authorizer.ex:693: Ash.Policy.Authorizer.strict_check/2
  (ash 3.5.25) lib/ash/can.ex:600: anonymous fn/5 in Ash.Can.run_check/4
  (elixir 1.17.2) lib/enum.ex:4858: Enumerable.List.reduce/3
  (elixir 1.17.2) lib/enum.ex:2585: Enum.reduce_while/3
  (ash 3.5.25) lib/ash/can.ex:597: Ash.Can.run_check/4
  (ash 3.5.25) lib/ash/can.ex:198: Ash.Can.can/4
  (ash 3.5.25) lib/ash.ex:1807: Ash.can/3

    nil.persisted(:data_layer)
    (spark 2.2.67) lib/spark/dsl/extension.ex:138: Spark.Dsl.Extension.persisted!/3
    (ash 3.5.25) lib/ash/filter/filter.ex:3881: Ash.Filter.do_hydrate_refs/2
    (ash 3.5.25) lib/ash/filter/filter.ex:3763: Ash.Filter.do_hydrate_refs/2
    (safari 0.1.0) lib/safari/policy/end_user_read_access.ex:2: Safari.Policy.EndUserReadAccess.try_strict_check/3
    (ash 3.5.25) lib/ash/policy/policy.ex:183: Ash.Policy.Policy.fetch_or_strict_check_fact/2
    (ash 3.5.25) lib/ash/policy/policy.ex:427: Ash.Policy.Policy.handle_constants/2
    (ash 3.5.25) lib/ash/policy/policy.ex:390: Ash.Policy.Policy.handle_constants/2
    (ash 3.5.25) lib/ash/policy/policy.ex:402: Ash.Policy.Policy.handle_constants/2
    (ash 3.5.25) lib/ash/policy/policy.ex:390: Ash.Policy.Policy.handle_constants/2
    (ash 3.5.25) lib/ash/policy/policy.ex:29: Ash.Policy.Policy.solve/1
    (ash 3.5.25) lib/ash/policy/checker.ex:65: Ash.Policy.Checker.strict_check_scenarios/1
    (ash 3.5.25) lib/ash/policy/authorizer/authorizer.ex:1724: Ash.Policy.Authorizer.strict_check_result/2
    (ash 3.5.25) lib/ash/policy/authorizer/authorizer.ex:693: Ash.Policy.Authorizer.strict_check/2
    (ash 3.5.25) lib/ash/can.ex:600: anonymous fn/5 in Ash.Can.run_check/4
    (elixir 1.17.2) lib/enum.ex:4858: Enumerable.List.reduce/3
    (elixir 1.17.2) lib/enum.ex:2585: Enum.reduce_while/3
    (ash 3.5.25) lib/ash/can.ex:597: Ash.Can.run_check/4
    (ash 3.5.25) lib/ash/can.ex:198: Ash.Can.can/4
    (ash 3.5.25) lib/ash.ex:1807: Ash.can/3

Reproduction

Just make an invalid exists.

Expected Behavior

Invalid exists either gives stack trace with information that the exists is wrongly done or it errors already at compile time.

[zimt28]

I was just about to open an issue because of a similar problem, but they should actually be the same: Misspelling the relationship name in exists causes the error you posted above without any hint where the error is coming from:

calculate :has_unpaid_invoice?,
          :boolean,
          expr(exists(subcription, unpaid_invoice?))

[olivermt]

It does say where it comes from (end user policy file), but its hidden in a lot of internal lines so its not super actionable.