Added alias support

Author: bbakerman

readme.md

@@ -180,6 +180,36 @@ For example, imagine a `phoneNumber` scalar like this :
 ```
 
 
+## Alias Scalars
+
+You can create aliases for existing scalars to add more semantic meaning to them.
+
+For example a link to a social media post could be representing by a `String` but the name `SocialMediaLink` is a 
+more semantically meaningful name for that scalar type.
+
+For example, you would build it like this:
+
+```java
+
+    AliasedScalar socialMediaLink = ExtendedScalars.newAliasedScalar("SocialMediaLink")
+            .aliasedScalar(Scalars.GraphQLString)
+            .build()
+
+```
+
+And use it in a SDL schema like this :
+
+```graphql
+
+     type Customer {
+           name : String
+           socialMediaLink : SocialMediaLink
+     }
+
+```
+
+Note: A future version of the graphql specification may add this capability but in the meantime you can use this facility.
+
 ## Other Scalars
 
 * `Url`

src/main/java/graphql/scalars/ExtendedScalars.java

@@ -1,6 +1,7 @@
 package graphql.scalars;
 
 import graphql.PublicApi;
+import graphql.scalars.alias.AliasedScalar;
 import graphql.scalars.datetime.DateScalar;
 import graphql.scalars.datetime.DateTimeScalar;
 import graphql.scalars.datetime.TimeScalar;
@@ -173,4 +174,28 @@ public class ExtendedScalars {
     public static RegexScalar.Builder newRegexScalar(String name) {
         return new RegexScalar.Builder().name(name);
     }
+
+    /**
+     * This allows an existing scalar to be wrapped and aliased with a new name.
+     * <p>
+     * For example you may take a `String` scalar and alias it as `SocialMediaLink` if that helps introduce
+     * more semantic meaning to your type system.
+     * <p>
+     * <pre>
+     * {@code
+     *
+     * type Customer {
+     *      name : String
+     *      socialMediaLink : SocialMediaLink
+     * }
+     * }
+     * </pre>
+     * <p>
+     * A future version of the graphql specification may add this capability but in the meantime you can use this facility.
+     *
+     * @return a builder of a aliased scalar
+     */
+    public static AliasedScalar.Builder newAliasedScalar(String name) {
+        return new AliasedScalar.Builder().name(name);
+    }
 }

src/main/java/graphql/scalars/alias/AliasedScalar.java

@@ -0,0 +1,101 @@
+package graphql.scalars.alias;
+
+import graphql.Assert;
+import graphql.Internal;
+import graphql.schema.Coercing;
+import graphql.schema.CoercingParseLiteralException;
+import graphql.schema.CoercingParseValueException;
+import graphql.schema.CoercingSerializeException;
+import graphql.schema.GraphQLScalarType;
+
+import java.util.Map;
+
+/**
+ * Access this via {@link graphql.scalars.ExtendedScalars#newAliasedScalar(String)}
+ */
+@Internal
+public class AliasedScalar extends GraphQLScalarType {
+
+    /**
+     * A builder for {@link graphql.scalars.alias.AliasedScalar}
+     */
+    public static class Builder {
+        private String name;
+        private String description;
+        private GraphQLScalarType aliasedScalar;
+
+        /**
+         * Sets the name of the aliased scalar
+         *
+         * @param name the name of the aliased scalar
+         *
+         * @return this builder
+         */
+        public Builder name(String name) {
+            this.name = name;
+            return this;
+        }
+
+        /**
+         * Sets the description of the aliased scalar
+         *
+         * @param description the description of the aliased scalar
+         *
+         * @return this builder
+         */
+        public Builder description(String description) {
+            this.description = description;
+            return this;
+        }
+
+        /**
+         * Sets the scalar that is to be aliased
+         *
+         * @param aliasedScalar the scalar that is to be aliased
+         *
+         * @return this builder
+         */
+        public Builder aliasedScalar(GraphQLScalarType aliasedScalar) {
+            this.aliasedScalar = aliasedScalar;
+            return this;
+        }
+
+        /**
+         * @return the built {@link AliasedScalar}
+         */
+        public AliasedScalar build() {
+            Assert.assertNotNull(name);
+            return aliasedScalarImpl(name, description, aliasedScalar);
+        }
+    }
+
+
+    private AliasedScalar(String name, String description, Coercing coercing) {
+        super(name, description, coercing);
+    }
+
+    private static AliasedScalar aliasedScalarImpl(String name, String description, GraphQLScalarType aliasedScalar) {
+        Assert.assertNotNull(aliasedScalar);
+        return new AliasedScalar(name, description, new Coercing<Object, Object>() {
+            @Override
+            public Object serialize(Object input) throws CoercingSerializeException {
+                return aliasedScalar.getCoercing().serialize(input);
+            }
+
+            @Override
+            public Object parseValue(Object input) throws CoercingParseValueException {
+                return aliasedScalar.getCoercing().parseValue(input);
+            }
+
+            @Override
+            public Object parseLiteral(Object input) throws CoercingParseLiteralException {
+                return aliasedScalar.getCoercing().parseLiteral(input);
+            }
+
+            @Override
+            public Object parseLiteral(Object input, Map<String, Object> variables) throws CoercingParseLiteralException {
+                return aliasedScalar.getCoercing().parseLiteral(input, variables);
+            }
+        });
+    }
+}

src/main/java/graphql/scalars/regex/RegexScalar.java

@@ -46,7 +46,7 @@ public Builder name(String name) {
         }
 
         /**
-         * Sets the name of the regex scalar
+         * Sets the description of the regex scalar
          *
          * @param description the description of the regex scalar
          *

src/test/groovy/graphql/scalars/alias/AliasedScalarTest.groovy

@@ -0,0 +1,37 @@
+package graphql.scalars.alias
+
+import graphql.Scalars
+import graphql.language.StringValue
+import graphql.scalars.ExtendedScalars
+import spock.lang.Specification
+
+class AliasedScalarTest extends Specification {
+
+    AliasedScalar socialMediaLink = ExtendedScalars.newAliasedScalar("SocialMediaLink")
+            .aliasedScalar(Scalars.GraphQLString)
+            .build()
+
+    def "basic wrapping"() {
+
+        when:
+        def result = socialMediaLink.coercing.serialize("ABC")
+        then:
+        result == "ABC"
+
+        when:
+        result = socialMediaLink.coercing.parseValue("ABC")
+        then:
+        result == "ABC"
+
+        when:
+        result = socialMediaLink.coercing.parseLiteral(new StringValue("ABC"))
+        then:
+        result == "ABC"
+
+        when:
+        result = socialMediaLink.coercing.parseLiteral(new StringValue("ABC"), [:])
+        then:
+        result == "ABC"
+
+    }
+}