null error annotating children with errors at stitching

[chess777]

I'm using graphql-tools-fork v7.0.3
NodeJS v12.8.1, tried also on v13.0.1
I have a following schema:

type Query {
  getType1(): Type1
}

type Type1 {
  type2: [Type2]!
}

type Type2{
  mandatoryField: String!
}

If I by error don't fill mandatoryField, then annotateWithChildrenErrors will fail with error:

{
  "stack": "TypeError: Cannot set property 'Symbol(subSchemaErrors)' of null\n    at annotateWithChildrenErrors (<path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\errors.ts:73:23)\n    at <path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\errors.ts:68:37\n    at Array.forEach (<anonymous>)\n    at Object.annotateWithChildrenErrors (<path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\errors.ts:68:12)\n    at Object.handleResult (<path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\checkResultAndHandleErrors.ts:63:5)\n    at defaultMergedResolver (<path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\defaultMergedResolver.ts:24:10)\n    at field.resolve (<path>api\\node_modules\\graphql-tools-fork\\src\\stitching\\mergeSchemas.ts:275:16)\n    at field.resolve (<path>api\\node_modules\\graphql-extensions\\src\\index.ts:274:18)\n    at resolveFieldValueOrError (<path>api\\node_modules\\graphql\\execution\\execute.js:467:18)\n    at resolveField (<path>api\\node_modules\\graphql\\execution\\execute.js:434:16)\n    at executeFields (<path>api\\node_modules\\graphql\\execution\\execute.js:275:18)\n    at collectAndExecuteSubfields (<path>api\\node_modules\\graphql\\execution\\execute.js:713:10)\n    at completeObjectValue (<path>api\\node_modules\\graphql\\execution\\execute.js:703:10)\n    at completeValue (<path>api\\node_modules\\graphql\\execution\\execute.js:591:12)\n    at completeValue (<path>api\\node_modules\\graphql\\execution\\execute.js:557:21)\n    at <path>api\\node_modules\\graphql\\execution\\execute.js:492:16",
  "message": "Cannot set property 'Symbol(subSchemaErrors)' of null"
}

After validation to annotateWithChildrenErrors comes object:

{
  type2: [
    null
  ]
}

And childrenErrors:

[
  {
    message: 'Cannot return null for non-nullable field Type2.mandatoryField.',
    path: ['type2', 0, 'mandatoryField']
  }
]

As error will be relocated it will reach such state when object is null and childrenErrors will still be an array - this will lead to null exception on line 73.
I've checked the code - v7.1.0 does not have it fixed.

[yaacovCR]

Fix only passes along the error if schemas is changed to

type Query {
  getType1(): Type1
}

type Type1 {
  type2: [Type2!]! // instead of [Type2]!
}

type Type2{
  mandatoryField: String!
}

[yaacovCR]

Does that work for now? I believe total fix requires wrapping stitched result instead of annotating it, because you can't annotate null, we get around that by throwing for fields immediately when null, but doesn't work with lists.

[chess777]

Thank you! The fix works as you've described.

[yaacovCR]

Should be fixed for reals now in 7.1.2.