Summary

This PR intentionally adds failing Spock tests for #3384.

It covers two paths:

• rebuilding a schema with GraphQLSchema.newSchema(schema).mutation((GraphQLObjectType) null).build()
• deleting the mutation root via SchemaTransformer.transformSchemaWithDeletes(...), which is the traversal-based schema modification API for delete operations

Both tests currently fail with the same NullPointerException in GraphQLTypeResolvingVisitor.visitGraphQLObjectType, reached from SchemaUtil.replaceTypeReferences.

Findings

The traversal-based variant does not avoid the problem. Even with transformSchemaWithDeletes(...), the rebuilt schema loses the Node interface from the type map while Person still has a resolved Node interface. During replaceTypeReferences, GraphQLTypeResolvingVisitor maps Person.getInterfaces() through the rebuilt type map and receives null for Node.

My current assumption is that the issue is in the schema rebuild/type collection path. In particular, GraphQLTypeCollectingVisitor accounts for dangling replaced strong references from fields, arguments, input fields, and applied directive arguments, but not from object/interface implemented interfaces. SchemaTransformer.DummyRoot.rebuildSchema(...) also only promotes changed extra types into additional types; in this repro Node is visited as an extra type but unchanged, so it is not retained as an additional type.

Verification

This command is expected to fail on this PR:

./gradlew test --tests "graphql.schema.impl.SchemaUtilTest.can rebuild schema after removing root type that made an implemented interface reachable" --tests "graphql.schema.impl.SchemaUtilTest.can transform schema after deleting root type that made an implemented interface reachable"

Observed result: 2 tests run, 2 failed, both in GraphQLTypeResolvingVisitor.visitGraphQLObjectType.

git diff --check passes.