How to handle custom scalar validation errors?

[ayushs-2k4]

I have created a custom scalar 'EmailScalar' which is as follows

`
import graphql.GraphQLContext;
import graphql.Internal;
import graphql.execution.CoercedVariables;
import graphql.language.StringValue;
import graphql.language.Value;
import graphql.schema.Coercing;
import graphql.schema.CoercingParseLiteralException;
import graphql.schema.CoercingSerializeException;
import graphql.schema.GraphQLScalarType;
import org.jetbrains.annotations.NotNull;

import java.util.Locale;

import static graphql.scalar.CoercingUtil.typeName;

@internal
public final class EmailScalar {

public static final GraphQLScalarType INSTANCE;

private EmailScalar() {
}

static {
    final Coercing<String, String> coercing = new Coercing<String, String>() {
        private String convertImpl(final Object input) {
            if (input instanceof String) {
                return (String) input;
            } else {
                throw new InvalidEmailFormatException("Invalid value '" + input + "' for Email");
            }
        }

        @Override
        public @NotNull String serialize(@NotNull final Object dataFetcherResult, @NotNull final GraphQLContext graphQLContext, @NotNull final Locale locale) throws CoercingSerializeException {
            final String stringValue = this.convertImpl(dataFetcherResult);
            if (!this.isValidEmail(stringValue)) {
                throw new InvalidEmailFormatException("Invalid value '" + stringValue + "' for Email");
            }
            return stringValue;
        }

        @Override
        public @NotNull String parseValue(@NotNull final Object input, @NotNull final GraphQLContext graphQLContext, @NotNull final Locale locale) {
            final String stringValue = this.convertImpl(input);
            if (!this.isValidEmail(stringValue)) {
                throw new InvalidEmailFormatException("Invalid email format: '" + stringValue + "'. Please provide a valid email.");
            }
            return stringValue;
        }

        @Override
        public @NotNull String parseLiteral(@NotNull final Value<?> input, @NotNull final CoercedVariables variables, @NotNull final GraphQLContext graphQLContext, @NotNull final Locale locale) throws CoercingParseLiteralException {
            if (input instanceof StringValue) {
                final String emailValue = ((StringValue) input).getValue();
                if (!this.isValidEmail(emailValue)) {
                    throw new InvalidEmailFormatException("Invalid email value: " + emailValue);
                }
                return emailValue;
            }
            throw new InvalidEmailFormatException("Expected AST type 'StringValue' but was '" + typeName(input) + "'.");
        }


        // Helper method to validate email format
        private boolean isValidEmail(final String email) {
            return email != null && email.contains("@");
            // For more advanced email validation, consider using a regex
        }
    };

    INSTANCE = GraphQLScalarType.newScalar()
            .name("Email")
            .description("A custom scalar that represents an email address.")
            .coercing(coercing)
            .build();
}

}
`

`
public class InvalidEmailFormatException extends RuntimeException {
public InvalidEmailFormatException(final String message) {
super(message);
}

public InvalidEmailFormatException() {
    super("Invalid Email!");
}

}
`

I am trying to handle it like other exceptions as:

`
@ControllerAdvice
public class CustomExceptionHandler {

@GraphQlExceptionHandler
public GraphQLError handle(final InvalidEmailFormatException exception) {
    return GraphQLError.newError()
            .message(exception.getMessage())
            .extensions(Map.of("code", "INVALID_EMAIL"))
            .build();
}

`

but this is not even getting called (other GraphQlExceptionHandlers are working perfectly). The output in client side is

{
"errors": [
{
"message": "500: Internal Server Error",
"extensions": {
"response": {
"url": "http://localhost:5155/graphql",
"status": 500,
"statusText": "Internal Server Error",
"body": {
"timestamp": "2024-09-28T17:02:59.823+00:00",
"status": 500,
"error": "Internal Server Error",
"trace": "com......"
"message": "Invalid email value: ayushsinghals09gmail.com",
"path": "/graphql"
}
},
"code": "INTERNAL_SERVER_ERROR"
}
}
],
"data": {
"login": null
}
}

and on server side is:

2024-09-28 22:43:49 DEBUG o.s.web.servlet.DispatcherServlet - Failed to complete request: com.ayushsinghal.kontestauthentication.graphql.InvalidEmailFormatException: Invalid email value: ayushsinghals09gmail.com
2024-09-28 22:43:49 ERROR o.a.c.c.C.[.[.[.[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: com.ayushsinghal.kontestauthentication.graphql.InvalidEmailFormatException: Invalid email value: ayushsinghals09gmail.com] with root cause
com.ayushsinghal.kontestauthentication.graphql.InvalidEmailFormatException: Invalid email value: ayushsinghals09gmail.com
at com.ayushsinghal.kontestauthentication.graphql.EmailScalar$1.parseLiteral(EmailScalar.java:59)
at com.ayushsinghal.kontestauthentication.graphql.EmailScalar$1.parseLiteral(EmailScalar.java:27)
at graphql.validation.ValidationUtil.parseLiteral(ValidationUtil.java:124)
at graphql.validation.ValidationUtil.isValidLiteralValue(ValidationUtil.java:96)
at graphql.validation.ValidationUtil.isValidLiteralValue(ValidationUtil.java:92)
at graphql.validation.ValidationUtil.isValidLiteralValue(ValidationUtil.java:153)
at graphql.validation.ValidationUtil.isValidLiteralValue(ValidationUtil.java:109)
at graphql.validation.ValidationUtil.isValidLiteralValue(ValidationUtil.java:92)
at graphql.validation.rules.ArgumentsOfCorrectType.checkArgument(ArgumentsOfCorrectType.java:31)
at graphql.validation.RulesVisitor.lambda$checkArgument$2(RulesVisitor.java:92)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1597)
at graphql.validation.RulesVisitor.checkArgument(RulesVisitor.java:92)
at graphql.validation.RulesVisitor.enter(RulesVisitor.java:61)
at graphql.validation.LanguageTraversal.traverseImpl(LanguageTraversal.java:33)
at graphql.validation.LanguageTraversal.traverseImpl(LanguageTraversal.java:38)
at graphql.validation.LanguageTraversal.traverseImpl(LanguageTraversal.java:38)
at graphql.validation.LanguageTraversal.traverseImpl(LanguageTraversal.java:38)
at graphql.validation.LanguageTraversal.traverseImpl(LanguageTraversal.java:38)
at graphql.validation.LanguageTraversal.traverse(LanguageTraversal.java:28)
at graphql.validation.Validator.validateDocument(Validator.java:82)
at graphql.ParseAndValidate.validate(ParseAndValidate.java:118)
at graphql.GraphQL.validate(GraphQL.java:531)
at graphql.GraphQL.parseAndValidate(GraphQL.java:497)
at graphql.GraphQL.lambda$parseValidateAndExecute$12(GraphQL.java:468)
at graphql.execution.preparsed.NoOpPreparsedDocumentProvider.getDocumentAsync(NoOpPreparsedDocumentProvider.java:16)
at graphql.GraphQL.parseValidateAndExecute(GraphQL.java:470)
at graphql.GraphQL.lambda$executeAsync$9(GraphQL.java:429)
at java.base/java.util.concurrent.CompletableFuture.uniComposeStage(CompletableFuture.java:1187)
at java.base/java.util.concurrent.CompletableFuture.thenCompose(CompletableFuture.java:2341)
at graphql.GraphQL.executeAsync(GraphQL.java:418)
at org.springframework.graphql.execution.DefaultExecutionGraphQlService.lambda$execute$2(DefaultExecutionGraphQlService.java:104)
at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:47)
at reactor.core.publisher.Mono.subscribe(Mono.java:4512)
at reactor.core.publisher.Mono.block(Mono.java:1727)
at com.netflix.graphql.dgs.springgraphql.webmvc.DgsWebMvcGraphQLInterceptor.intercept(DgsWebMvcGraphQLInterceptor.kt:78)
at org.springframework.graphql.server.WebGraphQlInterceptor.lambda$apply$2(WebGraphQlInterceptor.java:77)
at org.springframework.graphql.server.DefaultWebGraphQlHandlerBuilder$1.handleRequest(DefaultWebGraphQlHandlerBuilder.java:109)
at org.springframework.graphql.server.webmvc.AbstractGraphQlHttpHandler.handleRequest(AbstractGraphQlHttpHandler.java:123)
at org.springframework.web.servlet.function.support.HandlerFunctionAdapter.handle(HandlerFunctionAdapter.java:108)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914)
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885)
at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:110)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140)
at org.springframework.web.filter.CompositeFilter$VirtualFilterChain.doFilter(CompositeFilter.java:108)

Now my question is how to handle this type of error, I mean how to send custom graphql error response like we send with other errors?

[ayushs-2k4]

Specifically I want to handle GraphQL coercing errors.