I have a custom scalar type of `ClosedRange<Loc...

# graphql-kotlin

[rocketraman]

I have a custom scalar type of ClosedRange<LocalDate>. I have defined and registered a Coercing<ClosedRange<LocalDate>, String> (and via debugger confirmed the coercer is being called at runtime), but I get a Jackson exception when parsing an Input:

Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `kotlin.ranges.ClosedRange` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: my.MyInput["range"])

Any idea why that would be happening?

[Dariusz Kuc]

how did you define your ClosedRange<LocalDate> ? Jackson requires default (empty) constructor or you will have to annotate your data class

[rocketraman]

ClosedRange is a Kotlin stdlib type.

[rocketraman]

Maybe I misunderstand something about the interaction between coercers and Jackson. I thought if I defined a coercer then Jackson would not be invoked to instantiate that type, as my coercer instantiates it.

[rocketraman]

Could it have something to do with the fact that ClosedRange is an interface type? The underlying type is ComparableRange (private to stdlib).

[Dariusz Kuc]

where was it thrown? (from stacktrace)

[rocketraman]

at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:4236) ~[jackson-databind-2.11.4.jar:2.11.4]
	at com.fasterxml.jackson.databind.ObjectMapper.convertValue(ObjectMapper.java:4167) ~[jackson-databind-2.11.4.jar:2.11.4]
	at com.expediagroup.graphql.generator.execution.FunctionDataFetcher.convertValue(FunctionDataFetcher.kt:161) ~[graphql-kotlin-schema-generator-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.generator.execution.FunctionDataFetcher.convertArgumentToObject(FunctionDataFetcher.kt:142) ~[graphql-kotlin-schema-generator-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.generator.execution.FunctionDataFetcher.mapParameterToValue(FunctionDataFetcher.kt:114) ~[graphql-kotlin-schema-generator-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.generator.execution.FunctionDataFetcher.getParameters(FunctionDataFetcher.kt:90) ~[graphql-kotlin-schema-generator-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.generator.execution.FunctionDataFetcher.get(FunctionDataFetcher.kt:69) ~[graphql-kotlin-schema-generator-4.1.1.jar:4.1.1]
	at graphql.execution.ExecutionStrategy.fetchField(ExecutionStrategy.java:270) ~[graphql-java-16.2.jar:?]
	at graphql.execution.ExecutionStrategy.resolveFieldWithInfo(ExecutionStrategy.java:203) ~[graphql-java-16.2.jar:?]
	at graphql.execution.AsyncExecutionStrategy.execute(AsyncExecutionStrategy.java:60) ~[graphql-java-16.2.jar:?]
	at graphql.execution.ExecutionStrategy.completeValueForObject(ExecutionStrategy.java:646) ~[graphql-java-16.2.jar:?]
	at graphql.execution.ExecutionStrategy.completeValue(ExecutionStrategy.java:438) ~[graphql-java-16.2.jar:?]
	at graphql.execution.ExecutionStrategy.completeField(ExecutionStrategy.java:390) ~[graphql-java-16.2.jar:?]
	at graphql.execution.ExecutionStrategy.lambda$resolveFieldWithInfo$1(ExecutionStrategy.java:205) ~[graphql-java-16.2.jar:?]
	at java.util.concurrent.CompletableFuture.uniApplyNow(CompletableFuture.java:680) ~[?:?]
	at java.util.concurrent.CompletableFuture.uniApplyStage(CompletableFuture.java:658) ~[?:?]
	at java.util.concurrent.CompletableFuture.thenApply(CompletableFuture.java:2094) ~[?:?]
	at graphql.execution.ExecutionStrategy.resolveFieldWithInfo(ExecutionStrategy.java:204) ~[graphql-java-16.2.jar:?]
	at graphql.execution.AsyncExecutionStrategy.execute(AsyncExecutionStrategy.java:60) ~[graphql-java-16.2.jar:?]
	at graphql.execution.Execution.executeOperation(Execution.java:165) ~[graphql-java-16.2.jar:?]
	at graphql.execution.Execution.execute(Execution.java:104) ~[graphql-java-16.2.jar:?]
	at graphql.GraphQL.execute(GraphQL.java:557) ~[graphql-java-16.2.jar:?]
	at graphql.GraphQL.parseValidateAndExecute(GraphQL.java:482) ~[graphql-java-16.2.jar:?]
	at graphql.GraphQL.executeAsync(GraphQL.java:446) ~[graphql-java-16.2.jar:?]
	at com.expediagroup.graphql.server.execution.GraphQLRequestHandler.executeRequest$suspendImpl(GraphQLRequestHandler.kt:45) ~[graphql-kotlin-server-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.server.execution.GraphQLRequestHandler.executeRequest(GraphQLRequestHandler.kt) ~[graphql-kotlin-server-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.server.execution.GraphQLServer.execute$suspendImpl(GraphQLServer.kt:48) ~[graphql-kotlin-server-4.1.1.jar:4.1.1]
	at com.expediagroup.graphql.server.execution.GraphQLServer.execute(GraphQLServer.kt) ~[graphql-kotlin-server-4.1.1.jar:4.1.1]
	<my call handler here>
Caused by: com.fasterxml.jackson.databind.exc.InvalidDefinitionException:
	<jackson databind classes here>

[Dariusz Kuc]

ah so it is from https://github.com/ExpediaGroup/graphql-kotlin/blob/master/generator/graphql-kotli[…]expediagroup/graphql/generator/execution/FunctionDataFetcher.kt

[rocketraman]

Implying?

[Dariusz Kuc]

If I remember right* we had to add this logic to correctly cast the input arguments from data fetching environment

*it's been a while

[rocketraman]

So what are my options?

[Dariusz Kuc]

you could look into creating custom data fetcher that extends default function data fetcher and override mapParameterToValue with custom logic to handle closed range

[rocketraman]

Thx, I'll give it a shot

[rocketraman]

Hmm, the custom data fetcher operates on the parent type that contains the ClosedRange field. So do I need to add special logic for every type where I use ClosedRange (yuck)?

[Dariusz Kuc]

based on the above stacktrace issue is when using this custom scalar as input -> this implies that it is a function

[Dariusz Kuc]

so you need custom https://github.com/ExpediaGroup/graphql-kotlin/blob/master/generator/graphql-kotli[…]graphql/generator/execution/KotlinDataFetcherFactoryProvider.kt that creates an instance of your custom function data fetcher

[Dariusz Kuc]

for properties default data fetcher should be fine (and values should be automatically coerced)

[rocketraman]

Doesn't seem. ClosedRange is a property of my input data class type, and when mapParameterToValue is called, the param value is the input data class type. Just tried it with the debugger.

[Dariusz Kuc]

yeah if it is a property on the input class that logic there attempts to serialize the whole object

[Dariusz Kuc]

you could try annotating your input data class with custom serializer/converter info that describes how to handle the closed range

[rocketraman]

I tried to create a custom Jackson StdDeserializer but this is what seems to be happening:

serialized input on the wire
-> coercer deserializes into ClosedRange<LocalDate>
-> something serializes ClosedRange<LocalDate> into crazy JSON as the java.time objects have lots of internal state
-> custom deserializer runs with crazy JSON

[rocketraman]

I can certainly extract what I need from the crazy JSON, but this seems really inelegant and inefficient

[Shane Myrick]

You need to create your custom object mapper and make sure that gets passed in and used in the FunctionDataFetcher

https://github.com/ExpediaGroup/graphql-kotlin/blob/a6b957c999398c741cdfbc955fb862[…]expediagroup/graphql/generator/execution/FunctionDataFetcher.kt

As mentioned above, you can customize the how FunctionDataFetcher gets created with KotlinDataFetcherFactoryProvider

[rocketraman]

I tried that @Shane Myrick -- the FunctionDataFetcher gets the whole Input object, never just the ClosedRange<LocalDate> property. I'm not going to create custom fetchers for every object that happens to have a property of that type.

[rocketraman]

I created this issue with a working workaround, but there is some weird multi-level deserialization -> serialization -> deserialization happening: https://github.com/ExpediaGroup/graphql-kotlin/issues/1220.