Cannot generate SDL for :persistent_term schema

[dolfinus]

Environment

• Elixir version (elixir -v): 1.11.3
• Absinthe version (mix deps | grep absinthe): 1.6.3
• Client Framework and version (Relay, Apollo, etc): -

Expected behavior

If I try to execute absinthe.schema.sdl or absinthe.schema.json, I expect to see a file output:

absinthe.schema.sdl --schema ArkenstonWeb.Schema graphql/schema.graphql
# graphql/schema.graphql is created and filled up with schema SDL

absinthe.schema.json --schema ArkenstonWeb.Schema --pretty graphql/schema.json
# graphql/schema.json is created and filled up with schema JSON

Actual behavior

It is broken when I use a :persistent_term schema:
https://github.com/dolfinus/arkenston-backend/runs/2160087638

* creating graphql
* creating graphql/schema.graphql
** (ArgumentError) argument error
    :persistent_term.get({Absinthe.Schema.PersistentTerm, ArkenstonWeb.Schema})
    (absinthe 1.6.3) lib/absinthe/schema/persistent_term.ex:91: Absinthe.Schema.PersistentTerm.get/1
    (absinthe 1.6.3) lib/absinthe/schema/persistent_term.ex:51: Absinthe.Schema.PersistentTerm.__absinthe_type__/2
    (absinthe 1.6.3) lib/absinthe/phase/schema.ex:107: Absinthe.Phase.Schema.set_schema_node/4
    (absinthe 1.6.3) lib/absinthe/phase/schema.ex:71: anonymous fn/4 in Absinthe.Phase.Schema.set_children/3
    (absinthe 1.6.3) lib/absinthe/blueprint/transform.ex:16: anonymous fn/3 in Absinthe.Blueprint.Transform.prewalk/2
    (absinthe 1.6.3) lib/absinthe/blueprint/transform.ex:109: Absinthe.Blueprint.Transform.walk/4
    (elixir 1.11.3) lib/enum.ex:1533: Enum."-map_reduce/3-lists^mapfoldl/2-0-"/3

Relevant Schema/Middleware Code

https://github.com/dolfinus/arkenston-backend/blob/68b588fa0b56aaed256d4836a136e4cff1b6f25f/lib/arkenston_web/schema.ex#L1-L5

defmodule ArkenstonWeb.Schema do
  use Absinthe.Schema

  @schema_provider Absinthe.Schema.PersistentTerm
...
end

According to documentation https://hexdocs.pm/absinthe/Absinthe.Schema.PersistentTerm.html I've added this line to my supervisor tree:
https://github.com/dolfinus/arkenston-backend/blob/68b588fa0b56aaed256d4836a136e4cff1b6f25f/lib/arkenston/application.ex#L19

{Absinthe.Schema, MyAppWeb.Schema}

It works absolutely fine in staging or tests because Application is being started here.
But schema export command does not start it, and IMHO is should not do that because it may require to start too many things, like a database.

[binaryseed]

Right, the task doesn't start the app. I believe we can just start Absinthe.Schema with the schema module directly in the task, all it does is populate the persistent_term

[benwilson512]

@binaryseed shouldn't the on_load thing we did populate it without starting the genserver?

[dolfinus]

@benwilson512 Do you mean this @on_load which was added here #982 and then removed here 100ed9f ?

[binaryseed]

Yes there were some odd issues with that technique. I'd love to find one that didn't require users to put Absinthe.Schema in the supervision tree, though it's not the biggest deal

[benwilson512]

Ah I forgot it was removed.

[dolfinus]

Actually, I don't see any issues with @on_load usage for starting the scheme module. What do you think about returning it back?

[benwilson512]

@dolfinus I believe we ran into edge cases where it did not work. @binaryseed do you remember the details there?

[binaryseed]

The note I left when I reverted was this: #985 (comment)

I intend to try again though, it would be nice

[jordi-chacon]

Encountering exact same error when running absinthe.schema.json Mix task. This is preventing us is from using persistent_term. Curious if there are any workarounds or any plans to fix this issue in the next version of Absinthe?

[dolfinus]

It looks like #1159 fixed this issue

[connorjacobsen]

Interestingly, I still run into this error on 1.7.0 when running mix absinthe.schema.json --schema MySchema, but running mix absinthe.schema.sdl --schema MySchema works fine. I get the same error as the original comment.