Nondeterministic output when query and subscription return (non)nullable list elements

[zannen]

With the schema below, output is nondeterministic.

This behaviour occurs when a query returns a list of nullable things and a subscription returns a list of non-nullable things (or vice versa), the generated code for the subscription (it seems to always be the subscription) flips between using the normal function (marshalOThing2ᚖgqlgentestᚐThing) and the function with the null check (marshalNThing2ᚖgqlgentestᚐThing).

This behaviour does not occur:

• with two queries, one returning [Thing] and one returning [Thing!]
• with two subscriptions, one returning [Thing] and one returning [Thing!]
• with one query and one subscription, if Thing is replaced by String

What did you expect?

Deterministic output.

Minimal graphql.schema to reproduce

schema {
  query: Query
  subscription: Subscription
}

type Thing {id: Int}

type Query {
  things1: [Thing] # Note the "!" or lack thereof.
}

type Subscription {
  things2: [Thing!] # Note the "!" or lack thereof.
}

gqlgen.yml

---
schema: graphql.schema
exec:
  filename: generated.go
model:
  filename: models.go

Here's the script I've been using to test. Run it and wait for a while to see if files with different checksums get created.

rm -f *generated.go
while test "$(find -name '*-generated.go' | wc -l)" -lt 2 ; do
  date
  gqlgen -c gqlgen.yml
  cp -a generated.go "$(md5sum generated.go | awk '{print $1}')-generated.go"
  sleep 1
done

versions

• gqlgen version v0.10.1
• go version go1.11.13 linux/amd64
• dep or go modules? go modules: go.mod

  module gqlgentest
  
  require (
  	github.com/99designs/gqlgen v0.10.1
  	github.com/vektah/gqlparser v1.1.2
  )
  

[alexsn]

I have the exact some issue.

[zannen]

The template creating the code line that flips is codegen/type.gotpl L93.

Then we head to MarshalFunc then to UniquenessKey:

func (t *TypeReference) UniquenessKey() string {
	var nullability = "O"
	if t.GQL.NonNull {
		nullability = "N"
	}

	return nullability + t.Definition.Name + "2" + templates.TypeIdentifier(t.GO)
}

Let's see what's happening with t.GQL.NonNull.

[zannen]

PR #900 should fix this.

[colinschoen]

Pretty sure I am running into this too. Thanks for the PR @zannen.

[zannen]

Thanks @vektah.