graphql-multipart-request-spec is not followed fully

[vsfedorenko]

Summary

Hello, I am facing this issue. Please, check it first:
graphql-java-kickstart/graphql-java-servlet#260

Version
apollo-api-jvm:2.2.1

Description

I am getting the following exception:

java.lang.RuntimeException: expected null value when mapping variables.avatar
	at graphql.kickstart.servlet.core.internal.VariableMapper.mapVariable(VariableMapper.java:51) ~[graphql-java-servlet-9.2.0.jar:na]
	at graphql.kickstart.servlet.GraphQLMultipartInvocationInputParser.lambda$null$8(GraphQLMultipartInvocationInputParser.java:109) ~[graphql-java-servlet-9.2.0.jar:na]
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1510) ~[na:na]
	at graphql.kickstart.servlet.GraphQLMultipartInvocationInputParser.lambda$mapMultipartVariables$9(GraphQLMultipartInvocationInputParser.java:109) ~[graphql-java-servlet-9.2.0.jar:na]
	at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:723) ~[na:na]
	at graphql.kickstart.servlet.GraphQLMultipartInvocationInputParser.mapMultipartVariables(GraphQLMultipartInvocationInputParser.java:103) ~[graphql-java-servlet-9.2.0.jar:na]
	at graphql.kickstart.servlet.GraphQLMultipartInvocationInputParser.lambda$getGraphQLInvocationInput$2(GraphQLMultipartInvocationInputParser.java:77) ~[graphql-java-servlet-9.2.0.jar:na]
	at java.base/java.util.Optional.ifPresent(Optional.java:176) ~[na:na]
	at graphql.kickstart.servlet.GraphQLMultipartInvocationInputParser.getGraphQLInvocationInput(GraphQLMultipartInvocationInputParser.java:77) ~[graphql-java-servlet-9.2.0.jar:na]

This happens because during file upload you set the value to be equal mime type instead of setting it to be null like it is done in the spec: https://github.com/jaydenseric/graphql-multipart-request-spec.

I expect you to make it configurable or nullable. Also, this can be fixed at graphql-java-kickstart/graphql-java-servlet side, but technically, its you don't follow this spec, — not them: they expect it to be null as it must be. So, IMO, this should be fixed on your side first.

Thanks

[vsfedorenko]

Workaround: graphql-java-kickstart/graphql-java-servlet#260 (comment)