Does FilterCheck also raise an error?

Ash Forum Ash Questions / Help
1 
  policies do
    policy action_type(:read) do
      forbid_if expr(type(true, :boolean))
      authorize_if always()
    end
  end

I think forbid_if expr(type(true, :boolean)) is an inline filter policy,
so Ash.read!(ResourceModule) should return [],
but it raises an error.

** (Ash.Error.Forbidden) Forbidden Error

* forbidden
  (elixir 1.17.0) lib/process.ex:864: Process.info/2
  (ash 3.4.1) lib/ash/error/forbidden/policy.ex:9: Ash.Error.Forbidden.Policy."exception (overridable 2)"/1
  (ash 3.4.1) lib/ash/error/forbidden/policy.ex:28: Ash.Error.Forbidden.Policy.exception/1
  (ash 3.4.1) lib/ash/policy/authorizer/authorizer.ex:1529: Ash.Policy.Authorizer.strict_check_result/2
  (ash 3.4.1) lib/ash/policy/authorizer/authorizer.ex:617: Ash.Policy.Authorizer.strict_check/2
  (ash 3.4.1) lib/ash/can.ex:412: anonymous fn/6 in Ash.Can.run_check/4
  (elixir 1.17.0) lib/enum.ex:4858: Enumerable.List.reduce/3
  (elixir 1.17.0) lib/enum.ex:2585: Enum.reduce_while/3
  (ash 3.4.1) lib/ash/can.ex:409: Ash.Can.run_check/4
  (ash 3.4.1) lib/ash/can.ex:118: Ash.Can.can/4
  (ash 3.4.1) lib/ash.ex:1283: Ash.can/3
  (ash 3.4.1) lib/ash/actions/read/read.ex:1163: Ash.Actions.Read.authorize_query/2
  (ash 3.4.1) lib/ash/actions/read/read.ex:365: Ash.Actions.Read.do_read/4
  (ash 3.4.1) lib/ash/actions/read/read.ex:249: Ash.Actions.Read.do_run/3
  (ash 3.4.1) lib/ash/actions/read/read.ex:66: anonymous fn/3 in Ash.Actions.Read.run/3
  (ash 3.4.1) lib/ash/actions/read/read.ex:65: Ash.Actions.Read.run/3
  (ash 3.4.1) lib/ash.ex:1887: Ash.read/2
  (ash 3.4.1) lib/ash.ex:1846: Ash.read!/2
  (elixir 1.17.0) src/elixir.erl:386: :elixir.eval_external_handler/3
  (stdlib 6.0) erl_eval.erl:904: :erl_eval.do_apply/7
    (elixir 1.17.0) lib/process.ex:864: Process.info/2
    (ash 3.4.1) lib/ash/error/forbidden.ex:3: Ash.Error.Forbidden.exception/1
    (ash 3.4.1) /Users/r4f3works/fireworks/r3world/deps/splode/lib/splode.ex:211: Ash.Error.to_class/2
    (ash 3.4.1) lib/ash/error/error.ex:66: Ash.Error.to_error_class/2
    (ash 3.4.1) lib/ash/actions/read/read.ex:340: anonymous fn/3 in Ash.Actions.Read.do_run/3
    (ash 3.4.1) lib/ash/actions/read/read.ex:265: Ash.Actions.Read.do_run/3
    (ash 3.4.1) lib/ash/actions/read/read.ex:66: anonymous fn/3 in Ash.Actions.Read.run/3
    (ash 3.4.1) lib/ash/actions/read/read.ex:65: Ash.Actions.Read.run/3
    (ash 3.4.1) lib/ash.ex:1887: Ash.read/2
    (ash 3.4.1) lib/ash.ex:1846: Ash.read!/2
    iex:6: (file)

Is this an intended behavior?

2

:thinking: The primary issue here is that we are statically determining that the policy fails. A filter check will still raise an error if policies are statically false.

i.e forbid_if true is immediately incorrect, no queries must be made.

3

But I think the behavior of FilterPolicy should be predictable.
In some cases, raise error and in other cases, query and filter confuses me.

If I write a complex inline FilterPolicy,
something like expr(<statically determinable clause> and <dynamically determinable clause> and ...)
then this could be so hard to predict the result. @zachdaniel

4

…yes. You’re right. I’ll look into it.

5

@rapidfsub I’ve pushed something up to main that should make this consistent with the only exception of

authorize_if expr(boolean)
# or
authorize_if boolean

which will still be a static failure.

6

Okay, so this is actually going to have to be opt-in behavior so as to be backwards compatible. On the new version of Ash, you’d say:

  config :ash, :policy, no_filter_static_forbidden_reads?: false
7

In the future (e.g. ash 4.0), this would be a default behaviour?

8

Yes, it would be :slight_smile: