WIP Custom Scalar Proof of Concept

common/schema-builder/src/main/java/io/smallrye/graphql/schema/Annotations.java

@@ -586,6 +586,7 @@ private static Map<DotName, AnnotationInstance> getAnnotationsWithFilter(org.jbo
 
     // SmallRye GraphQL Annotations (Experimental)
     public static final DotName TO_SCALAR = DotName.createSimple("io.smallrye.graphql.api.ToScalar"); // TODO: Remove
+    public static final DotName CUSTOM_SCALAR = DotName.createSimple("io.smallrye.graphql.api.CustomScalar");
     public static final DotName ADAPT_TO_SCALAR = DotName.createSimple("io.smallrye.graphql.api.AdaptToScalar");
     public static final DotName ADAPT_WITH = DotName.createSimple("io.smallrye.graphql.api.AdaptWith");
     public static final DotName ERROR_CODE = DotName.createSimple("io.smallrye.graphql.api.ErrorCode");

common/schema-builder/src/main/java/io/smallrye/graphql/schema/SchemaBuilder.java

@@ -1,5 +1,6 @@
 package io.smallrye.graphql.schema;
 
+import static io.smallrye.graphql.schema.Annotations.CUSTOM_SCALAR;
 import static io.smallrye.graphql.schema.Annotations.DIRECTIVE;
 
 import java.util.ArrayList;
@@ -28,6 +29,7 @@
 import io.smallrye.graphql.schema.creator.OperationCreator;
 import io.smallrye.graphql.schema.creator.ReferenceCreator;
 import io.smallrye.graphql.schema.creator.type.Creator;
+import io.smallrye.graphql.schema.creator.type.CustomScalarCreator;
 import io.smallrye.graphql.schema.creator.type.EnumCreator;
 import io.smallrye.graphql.schema.creator.type.InputTypeCreator;
 import io.smallrye.graphql.schema.creator.type.InterfaceCreator;
@@ -73,6 +75,7 @@ public class SchemaBuilder {
     private final OperationCreator operationCreator;
     private final DirectiveTypeCreator directiveTypeCreator;
     private final UnionCreator unionCreator;
+    private final CustomScalarCreator customScalarCreator;
 
     private final DotName FEDERATION_ANNOTATIONS_PACKAGE = DotName.createSimple("io.smallrye.graphql.api.federation");
 
@@ -109,6 +112,7 @@ private SchemaBuilder(TypeAutoNameStrategy autoNameStrategy) {
         interfaceCreator = new InterfaceCreator(referenceCreator, fieldCreator, operationCreator);
         directiveTypeCreator = new DirectiveTypeCreator(referenceCreator);
         unionCreator = new UnionCreator(referenceCreator);
+        customScalarCreator = new CustomScalarCreator(referenceCreator);
     }
 
     private Schema generateSchema() {
@@ -127,6 +131,8 @@ private Schema generateSchema() {
         // add AppliedSchemaDirectives and Schema Description
         setUpSchemaDirectivesAndDescription(schema, graphQLApiAnnotations, directivesHelper);
 
+        addCustomScalarTypes(schema);
+
         for (AnnotationInstance graphQLApiAnnotation : graphQLApiAnnotations) {
             ClassInfo apiClass = graphQLApiAnnotation.target().asClass();
             List<MethodInfo> methods = getAllMethodsIncludingFromSuperClasses(apiClass);
@@ -187,7 +193,18 @@ private void addDirectiveTypes(Schema schema) {
         schema.addDirectiveType(RolesAllowedDirectivesHelper.ROLES_ALLOWED_DIRECTIVE_TYPE);
     }
 
+    private void addCustomScalarTypes(Schema schema) {
+        Collection<AnnotationInstance> annotations = ScanningContext.getIndex().getAnnotations(CUSTOM_SCALAR);
+
+        for (AnnotationInstance annotationInstance : annotations) {
+            schema.addCustomScalarType(customScalarCreator.create(
+                    annotationInstance.target().asClass(),
+                    annotationInstance.value().asString()));
+        }
+    }
+
     private void setupDirectives(Directives directives) {
+        customScalarCreator.setDirectives(directives);
         inputTypeCreator.setDirectives(directives);
         typeCreator.setDirectives(directives);
         interfaceCreator.setDirectives(directives);

common/schema-builder/src/main/java/io/smallrye/graphql/schema/creator/type/CustomScalarCreator.java

@@ -0,0 +1,92 @@
+package io.smallrye.graphql.schema.creator.type;
+
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.FLOAT_TYPE;
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.INT_TYPE;
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.STRING_TYPE;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.jboss.jandex.ClassInfo;
+import org.jboss.jandex.ClassType;
+import org.jboss.jandex.DotName;
+import org.jboss.logging.Logger;
+
+import io.smallrye.graphql.schema.Annotations;
+import io.smallrye.graphql.schema.creator.ModelCreator;
+import io.smallrye.graphql.schema.creator.ReferenceCreator;
+import io.smallrye.graphql.schema.helper.DescriptionHelper;
+import io.smallrye.graphql.schema.helper.Directives;
+import io.smallrye.graphql.schema.model.CustomScalarType;
+import io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType;
+import io.smallrye.graphql.schema.model.DirectiveInstance;
+
+public class CustomScalarCreator extends ModelCreator {
+
+    private static final Logger LOG = Logger.getLogger(CustomScalarCreator.class.getName());
+
+    private Directives directives;
+
+    public CustomScalarCreator(ReferenceCreator referenceCreator) {
+        super(referenceCreator);
+    }
+
+    public CustomScalarType create(
+            ClassInfo classInfo,
+            String scalarName) {
+        LOG.debug("Creating custom scalar from " + classInfo.name().toString());
+
+        Annotations annotations = Annotations.getAnnotationsForClass(classInfo);
+
+        Set<String> interfaces = classInfo.interfaceNames().stream().map(DotName::toString)
+                .collect(Collectors.toSet());
+        CustomScalarPrimitiveType customScalarPrimitiveType;
+        if (interfaces.contains("io.smallrye.graphql.scalar.custom.CustomIntScalar")) {
+            checkForOneArgConstructor(classInfo, BigInteger.class);
+            customScalarPrimitiveType = INT_TYPE;
+        } else if (interfaces.contains("io.smallrye.graphql.scalar.custom.CustomFloatScalar")) {
+            checkForOneArgConstructor(classInfo, BigDecimal.class);
+            customScalarPrimitiveType = FLOAT_TYPE;
+        } else if (interfaces.contains("io.smallrye.graphql.scalar.custom.CustomStringScalar")) {
+            checkForOneArgConstructor(classInfo, String.class);
+            customScalarPrimitiveType = STRING_TYPE;
+        } else {
+            //TODO error handle in the expected way
+            throw new RuntimeException("Required to implement a known CustomScalar primitive type. "
+                    + "(CustomStringScalar, CustomFloatScalar, CustomIntScalar)");
+        }
+
+        return new CustomScalarType(
+                classInfo.name().toString(),
+                scalarName,
+                DescriptionHelper.getDescriptionForType(annotations).orElse(null),
+                customScalarPrimitiveType);
+
+    }
+
+    private static void checkForOneArgConstructor(final ClassInfo classInfo, Class<?> argType) {
+        if (classInfo.constructors().stream().noneMatch(methodInfo -> methodInfo.parameters().size() == 1
+                && methodInfo.parameterType(0).equals(ClassType.create(argType)))) {
+            //TODO error handle in the expected way
+            throw new RuntimeException("Required to implement a one arg constructor with paramtype of "
+                    + argType.getName());
+        }
+    }
+
+    @Override
+    public String getDirectiveLocation() {
+        return "SCALAR";
+    }
+
+    private List<DirectiveInstance> getDirectiveInstances(Annotations annotations,
+            String referenceName) {
+        return directives.buildDirectiveInstances(annotations, getDirectiveLocation(), referenceName);
+    }
+
+    public void setDirectives(Directives directives) {
+        this.directives = directives;
+    }
+}

common/schema-model/src/main/java/io/smallrye/graphql/schema/model/CustomScalarType.java

@@ -0,0 +1,52 @@
+package io.smallrye.graphql.schema.model;
+
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.FLOAT_TYPE;
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.INT_TYPE;
+import static io.smallrye.graphql.schema.model.CustomScalarType.CustomScalarPrimitiveType.STRING_TYPE;
+
+public final class CustomScalarType extends Reference {
+
+    private String description;
+    private CustomScalarPrimitiveType customScalarPrimitiveType;
+
+    public CustomScalarType() {
+    }
+
+    public CustomScalarType(String className, String name, String description,
+            CustomScalarPrimitiveType customScalarPrimitiveType) {
+        super(className, name, ReferenceType.SCALAR);
+        this.description = description;
+        this.customScalarPrimitiveType = customScalarPrimitiveType;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public CustomScalarPrimitiveType getCustomScalarPrimitiveType() {
+        return customScalarPrimitiveType;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public void setCustomScalarPrimitiveType(CustomScalarPrimitiveType customScalarPrimitiveType) {
+        this.customScalarPrimitiveType = customScalarPrimitiveType;
+    }
+
+    @Override
+    public String toString() {
+        return "CustomScalarType{" +
+                "name='" + getName() + '\'' +
+                ", description='" + description + '\'' +
+                ", customScalar='" + customScalarPrimitiveType.name() + '\'' +
+                '}';
+    }
+
+    public enum CustomScalarPrimitiveType {
+        STRING_TYPE,
+        INT_TYPE,
+        FLOAT_TYPE
+    }
+}

common/schema-model/src/main/java/io/smallrye/graphql/schema/model/Scalars.java

@@ -94,6 +94,12 @@ public static Reference getIDScalar(String className) {
                 .build();
     }
 
+    public static void registerCustomScalarInSchema(
+            String graphQlScalarName,
+            String valueClassName) {
+        populateScalar(valueClassName, graphQlScalarName, valueClassName);
+    }
+
     // this is for the UUID from graphql-java-extended-scalars
     // if used, it will override the original UUID type that is mapped to a String in the schema
     public static void addUuid() {

common/schema-model/src/main/java/io/smallrye/graphql/schema/model/Schema.java

@@ -26,6 +26,7 @@ public final class Schema implements Serializable {
     private Map<Group, Set<Operation>> groupedMutations = new HashMap<>();
     private Map<Group, Set<Operation>> groupedSubscriptions = new HashMap<>();
 
+    private List<CustomScalarType> customScalarTypes = new ArrayList<>();
     private List<DirectiveType> directiveTypes = new ArrayList<>();
     private Map<String, InputType> inputs = new HashMap<>();
     private Map<String, Type> types = new HashMap<>();
@@ -320,6 +321,21 @@ private void addToOperationMap(Map<Group, Set<Operation>> map, Group group, Oper
         map.put(group, set);
     }
 
+    public void addCustomScalarType(CustomScalarType customScalarType) {
+        customScalarTypes.add(customScalarType);
+        Scalars.registerCustomScalarInSchema(
+                customScalarType.getName(),
+                customScalarType.getClassName());
+    }
+
+    public List<CustomScalarType> getCustomScalarTypes() {
+        return customScalarTypes;
+    }
+
+    public boolean hasCustomScalarTypes() {
+        return !customScalarTypes.isEmpty();
+    }
+
     public List<DirectiveType> getDirectiveTypes() {
         return directiveTypes;
     }
@@ -347,6 +363,7 @@ public String toString() {
                 ", groupedMutations=" + groupedMutations +
                 ", groupedSubscriptions=" + groupedSubscriptions +
                 ", directiveTypes=" + directiveTypes +
+                ", customScalarTypes=" + customScalarTypes +
                 ", inputs=" + inputs +
                 ", types=" + types +
                 ", interfaces=" + interfaces +

docs/custom-scalar.md

@@ -0,0 +1,28 @@
+Creating GraphQL Custom Scalars with SmallRye GraphQL
+=======
+While by default **MicroProfile GraphQL** specification doesn't provide direct support for creating
+custom scalars for GraphQL literal types of String, Int and Float, **SmallRye GraphQL** has implemented 
+this feature based on user feedback. To implement a **custom scalar** with **SmallRye GraphQL**, 
+you can annotate your custom scalar class with `@CustomScalar` in addition to following the pattern below:
+```java
+  @CustomScalar("BigDecimalString")
+  public class BigDecimalString implements CustomStringScalar {
+    public BigDecimalString(String stringValue) {
+        ...
+    }
+    @Override
+    public String stringValueForSerialization() {
+        ...
+  }
+}
+```
+In this example, `BigDecimalString` implements the `CustomStringScalar` which is used to identify the 
+proper (de) serialization for BigDecimalString.  `BigDecimalString` also provides a single argument
+constructor which takes a String.  Finally, `BigDecimalString` implements 
+`stringValueForSerialization()` which provides the String representation to be used during 
+serialization.
+
+> [NOTE]
+> If the user wants to create a literal for GraphQL Int or Float, they would implement either 
+> CustomIntScalar with the intValueForSerialization method or CustomFloatScalar with the
+> floatValueForSerialization method respectively.

server/api/src/main/java/io/smallrye/graphql/api/CustomScalar.java

@@ -0,0 +1,22 @@
+package io.smallrye.graphql.api;
+
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import io.smallrye.common.annotation.Experimental;
+
+/**
+ * Allows for definition of custom graphql scalars.  Types with this annotation should extend one of
+ * CustomStringScalar, CustomIntScalar, or CustomFloatScalar.  Additionally, the Type should provide
+ * a single argument constructor taking the associated type(String, BigInteger, BigDecimal).
+ */
+@Retention(RUNTIME)
+@Target(TYPE)
+@Experimental("Mark a type as a custom scalar with the given name in the GraphQL schema.")
+public @interface CustomScalar {
+
+    String value();
+}