More customizable errors would be nice

It’s currently impossible to report errors whose message does not start with "Exception while fetching data: ".

Overriding ExecutionStrategy.resolveField is a bad workaround (and see #208).

[dminkovsky]

FWIW, here’s a Jackson serializer (if anyone is using Jackson) for ExecutionResult that will skip printing the stacks if an error is an ExceptionWhileDataFetching:

Implementation:

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;
import graphql.ExecutionResult;
import graphql.GraphQLError;
import graphql.language.SourceLocation;

import java.io.IOException;
import java.util.List;

public class ExecutionResultSerializer extends StdSerializer<ExecutionResult> {

    public ExecutionResultSerializer() {
        this(null);
    }

    public ExecutionResultSerializer(Class<ExecutionResult> t) {
        super(t);
    }

    @Override
    public void serialize(ExecutionResult executionResult, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
        Object data = executionResult.getData();
        jsonGenerator.writeStartObject();
        if (data != null) {
            jsonGenerator.writeObjectField("data", data);
        }
        List<GraphQLError> errors = executionResult.getErrors();
        if (errors != null && !errors.isEmpty()) {
            jsonGenerator.writeArrayFieldStart("errors");
            for (GraphQLError error : errors) {
                jsonGenerator.writeStartObject();
                jsonGenerator.writeFieldName("message");
                jsonGenerator.writeString(error.getMessage());
                List<SourceLocation> locations = error.getLocations();
                if (!locations.isEmpty()) {
                    jsonGenerator.writeArrayFieldStart("locations");
                    for (SourceLocation location : locations) {
                        jsonGenerator.writeObject(location);
                    }
                    jsonGenerator.writeEndArray();
                }
                jsonGenerator.writeEndObject();
            }
            jsonGenerator.writeEndArray();
        }
        jsonGenerator.writeEndObject();
    }
}

Test:

import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.databind.module.SimpleModule
import graphql.ErrorType
import graphql.ExecutionResult
import graphql.ExecutionResultImpl
import graphql.GraphQLError
import graphql.language.SourceLocation
import org.skyscreamer.jsonassert.JSONAssert
import spock.lang.Specification


class ExecutionResultSerializerTest extends Specification {

    def mapper = new ObjectMapper()

    def setup() {
        SimpleModule module = new SimpleModule()
        module.addSerializer(ExecutionResult.class, new ExecutionResultSerializer())
        mapper.registerModule(module)
    }

    def "data and errors null"() {
        given:
        def result = new ExecutionResultImpl(null, null)

        when:
        def serialized = mapper.writeValueAsString(result)

        then:
        JSONAssert.assertEquals('{}', serialized, false)
    }

    def "just data"() {
        given:
        def result = new ExecutionResultImpl([field: 'value'], null)

        when:
        def serialized = mapper.writeValueAsString(result);

        then:
        JSONAssert.assertEquals('{ "data": { "field": "value" } }', serialized, true)
    }

    def "just errors"() {
        given:

        def result = new ExecutionResultImpl(null, [
          new GraphQLError() {

              @Override
              String getMessage() {
                  return "message"
              }

              @Override
              List<SourceLocation> getLocations() {
                  return [new SourceLocation(1, 1)]
              }

              @Override
              ErrorType getErrorType() {
                  return null
              }
          }
        ])

        when:
        def serialized = mapper.writeValueAsString(result)

        then:
        JSONAssert.assertEquals('{ "errors": [ { "message": "message", "locations": [ { "column": 1, "line": 1 } ] } ] }', serialized, true)
    }

    def "data and errors"() {

        def result = new ExecutionResultImpl([field: 'value'], [
          new GraphQLError() {

              @Override
              String getMessage() {
                  return "message"
              }

              @Override
              List<SourceLocation> getLocations() {
                  return [new SourceLocation(1, 1)]
              }

              @Override
              ErrorType getErrorType() {
                  return null
              }
          }
        ])

        when:
        def serialized = mapper.writeValueAsString(result)

        then:
        JSONAssert.assertEquals('{ "data": { "field": "value" }, "errors": [ { "message": "message", "locations": [ { "column": 1, "line": 1 } ] } ] }', serialized, true)

    }
}

[jonerer]

@dminkovsky thanks! I was looking for something similar. I won’t want risk exposing internals by showing a stacktrace. Your code worked fine except for one thing: Had to change if (!locations.isEmpty()) { into if (locations != null && !locations.isEmpty()) {

Or I’d get NPEs while serializing (in my case a dataFetcher threw an IllegalArgumentException), and “location” was null