Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

toReadOnlySchema() fails on schemas with interfaces, unions or custom directives

Open
  • Is something wrong?
#896 0 comments 0 reactions 0 assignees View on GitHub

Maintainers usually reply within 1 day

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
74/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
graphql, kotlin
Domain
backend-api-design

Research direction

Start by comparing SchemaObjects#toReadOnlySchema() with toSchema(), which the issue identifies as passing the code registry and directives. Check for existing tests around parseSchemaObjects() and add coverage for interfaces, unions, and applied custom directives. Done means toReadOnlySchema() builds those schemas successfully without mutation or subscription support.

Written by the indexing model from the issue text.

Description

bug

SchemaObjects#toReadOnlySchema() throws for any schema with an interface, a union or an applied custom directive. Same on graphql-java 26.1 and 25.1:

Schema parseSchemaObjects().toReadOnlySchema()
scalar fields only, or @deprecated builds
interface Animal AssertException: There must be a type resolver for interface Animal
union Pet = Dog AssertException: There must be a type resolver for union Pet
name: String @tag with directive @tag on FIELD_DEFINITION InvalidSchemaException: invalid schema: A definition for directive 'tag' could not be found

It only passes the query type and the dictionary to GraphQLSchema.newSchema(), and toSchema() got the extra parts it needed over time but toReadOnlySchema() never did:

  1. Since 5.6.1 (e6f6f4d, the move to graphql-java 13) the type resolvers live in the code registry instead of on the interface and union types. toSchema() started passing codeRegistryBuilder.build(), toReadOnlySchema() doesn't pass a code registry at all.
  2. graphql-java 18.0 started rejecting applied directives without a definition in the schema (graphql-java/graphql-java#2576). 71b9752 added additionalDirectives(directives) to toSchema() for that in 12.1.0, but not to toReadOnlySchema().

So it's been broken for interfaces and unions since 2019, and for custom directives since 12.1.0. I couldn't find a caller in this org, there's no test for it and nobody reported it, so probably nobody uses it.

Fix would be to pass the same code registry, directives and schema applied directives as toSchema(), just without mutation and subscription. Or deprecate it.

Dominant language
Kotlin
Stars
824
Forks
175
Avg merge
2d 5h
Merged PRs (30d)
52

Getting set up

This project ships no dev container, Dockerfile or contributing guide, so setting up is up to you: start from its README, and see our first-contribution guide for the general steps.

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from graphql-java-kickstart/graphql-java-tools

All issues in graphql-java-kickstart/graphql-java-tools

Similar issues

More Kotlin issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.