Help needed debugging NonNullableValueCoercedAsNullException #2760

slisaasquatch · 2022-03-11T22:32:17Z

slisaasquatch
Mar 11, 2022

I'm seeing random NonNullableValueCoercedAsNullExceptions from our servers running graphql-java 17.3 with graphql-java-tools 12.0.2. I've logged the entire GraphQL query, variables, and operation name, and I cannot reproduce the exception. The stack trace looks like this:

graphql.execution.NonNullableValueCoercedAsNullException: Field '' has coerced Null value for NonNull type 'String!'
	at graphql.execution.ValuesResolver.externalValueToInternalValue(ValuesResolver.java:493)
	at graphql.execution.ValuesResolver.lambda$externalValueToInternalValueForList$2(ValuesResolver.java:604)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:566)
	at graphql.execution.ValuesResolver.externalValueToInternalValueForList(ValuesResolver.java:605)
	at graphql.execution.ValuesResolver.externalValueToInternalValue(ValuesResolver.java:507)
	at graphql.execution.ValuesResolver.externalValueToInternalValueForObject(ValuesResolver.java:570)
	at graphql.execution.ValuesResolver.externalValueToInternalValue(ValuesResolver.java:510)
	at graphql.execution.ValuesResolver.externalValueToInternalValue(ValuesResolver.java:491)
	at graphql.execution.ValuesResolver.externalValueToInternalValueForVariables(ValuesResolver.java:412)
	at graphql.execution.ValuesResolver.coerceVariableValues(ValuesResolver.java:94)
	at graphql.analysis.QueryTraverser.coerceVariables(QueryTraverser.java:64)
	at graphql.analysis.QueryTraverser.<init>(QueryTraverser.java:60)
	at graphql.analysis.QueryTraverser.<init>(QueryTraverser.java:40)
	at graphql.analysis.QueryTraverser$Builder.build(QueryTraverser.java:297)
	at graphql.analysis.MaxQueryDepthInstrumentation.newQueryTraverser(MaxQueryDepthInstrumentation.java:92)
	at graphql.analysis.MaxQueryDepthInstrumentation.lambda$beginValidation$2(MaxQueryDepthInstrumentation.java:57)
	at graphql.execution.instrumentation.SimpleInstrumentationContext.onCompleted(SimpleInstrumentationContext.java:51)
	at graphql.execution.instrumentation.ChainedInstrumentation$ChainedInstrumentationContext.lambda$onCompleted$1(ChainedInstrumentation.java:238)
	at graphql.com.google.common.collect.ImmutableList.forEach(ImmutableList.java:405)
	at graphql.execution.instrumentation.ChainedInstrumentation$ChainedInstrumentationContext.onCompleted(ChainedInstrumentation.java:238)
	at graphql.GraphQL.validate(GraphQL.java:600)
	at graphql.GraphQL.parseAndValidate(GraphQL.java:562)
	at graphql.GraphQL.lambda$parseValidateAndExecute$10(GraphQL.java:531)
	at graphql.execution.preparsed.NoOpPreparsedDocumentProvider.getDocument(NoOpPreparsedDocumentProvider.java:15)
	at graphql.GraphQL.parseValidateAndExecute(GraphQL.java:533)
	at graphql.GraphQL.executeAsync(GraphQL.java:502)

Can someone please give me some general directions on what the error means?

I know if I put a null inside an array that requires non null values in variables, I can cause an error with the same error message. However, if you look at the stack trace, the exception was thrown at graphql.GraphQL.executeAsync, meaning I'm not even getting a result from it.

Also for the record, this is what my variables looks like:

{
  "accountId": "133...63",
  "userId": "133...63",
  "userInput": {
    "accountId": "133...63",
    "id": "133...63"
  }
}

I do not have arrays or nulls in my variables.

Answered by bbakerman

Mar 13, 2022

Let me give you some generalised information about NonNullableValueCoercedAsNullException and then I will look further.

NonNullableValueCoercedAsNullException is thrown when a field that declares itself to be non nullable in fact at runtime does return a null value (say name : String! which then returns a null name value say)

However looking at this stack trace I can see its no field execution but rather the MaxQueryDepthInstrumentation traversing a input query and trying to get certain values.

(The Field '' has coerced Null is a bug - we should fix that useless error message)

I am a little puzzled here because this is "input arguments" and not output field values.

I need to sit down and…

View full answer

abbosbek776 · 2022-03-12T13:47:34Z

abbosbek776
Mar 12, 2022

Did you solve your issue yet?

1 reply

slisaasquatch Mar 12, 2022
Author

No, not yet.

bbakerman · 2022-03-13T01:03:34Z

bbakerman
Mar 13, 2022
Collaborator

Let me give you some generalised information about NonNullableValueCoercedAsNullException and then I will look further.

NonNullableValueCoercedAsNullException is thrown when a field that declares itself to be non nullable in fact at runtime does return a null value (say name : String! which then returns a null name value say)

However looking at this stack trace I can see its no field execution but rather the MaxQueryDepthInstrumentation traversing a input query and trying to get certain values.

(The Field '' has coerced Null is a bug - we should fix that useless error message)

I am a little puzzled here because this is "input arguments" and not output field values.

I need to sit down and spend some time on this to find a cause.

(also as an aside I think we have an opportunity to make this "field argument value" work lazy. MaxQueryDepthInstrumentation code is not interested in argument values and hence this should be lazy in the QueryTraverser... but thats another improvement for another time)

2 replies

bbakerman Mar 13, 2022
Collaborator

I have created an issue fior this. I will discuss it more on the issue.

bbakerman Mar 13, 2022
Collaborator

See my comment there about possible custom scalars breaking contract

slisaasquatch · 2022-03-14T17:35:00Z

slisaasquatch
Mar 14, 2022
Author

This turned out to be my own fault, because the variables was actually

{
"accountId": "133...63",
"userId": "133...63",
"userInput": {
"accountId": "133...63",
"id": "133...63",
"referredByCodes": [null]
}
}
And the referredByCodes field got lost in our logging framework, and it's now obvious that that's what's causing the problem.

0 replies

bbakerman · 2022-03-15T09:40:55Z

bbakerman
Mar 15, 2022
Collaborator

Thanks for getting back. The exception messages are rubbish (no field name etc..) so that needs to be improved

0 replies

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