account for jsonUrl being null in type signature

src/main/java/edu/wpi/first/nativeutils/vendordeps/OptionalTypeAdapter.java

@@ -0,0 +1,57 @@
+// modified from https://stackoverflow.com/questions/12161366/how-to-serialize-optionalt-classes-with-gson
+package edu.wpi.first.nativeutils.vendordeps;
+
+import java.io.IOException;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.Optional;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
+import com.google.gson.stream.JsonWriter;
+
+class OptionalTypeAdapter<E> extends TypeAdapter<Optional<E>> {
+    public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
+        @SuppressWarnings("unchecked")
+        @Override
+        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+            Class<T> rawType = (Class<T>) type.getRawType().getClass();
+            if (rawType != Optional.class) {
+                return null;
+            }
+            final ParameterizedType parameterizedType = (ParameterizedType) type.getType();
+            final Type actualType = parameterizedType.getActualTypeArguments()[0];
+            final TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(actualType));
+            return new OptionalTypeAdapter(adapter);
+        }
+    };
+    private final TypeAdapter<E> adapter;
+
+    public OptionalTypeAdapter(TypeAdapter<E> adapter) {
+        this.adapter = adapter;
+    }
+
+    @Override
+    public void write(JsonWriter out, Optional<E> value) throws IOException {
+        if(value.isPresent()){
+            adapter.write(out, value.get());
+        } else {
+            out.nullValue();
+        }
+    }
+
+    @Override
+    public Optional<E> read(JsonReader in) throws IOException {
+        final JsonToken peek = in.peek();
+        if(peek != JsonToken.NULL){
+            return Optional.ofNullable(adapter.read(in));
+        }
+
+        in.nextNull();
+        return Optional.empty();
+    }
+}

src/main/java/edu/wpi/first/nativeutils/vendordeps/WPIVendorDepsExtension.java

@@ -5,6 +5,7 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.util.Arrays;
+import java.util.Optional;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -21,6 +22,7 @@
 import org.gradle.nativeplatform.plugins.NativeComponentPlugin;
 
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 
 import edu.wpi.first.deployutils.log.ETLogger;
 import edu.wpi.first.deployutils.log.ETLoggerFactory;
@@ -47,7 +49,7 @@ public NamedDomainObjectSet<NamedJsonDependency> getDependencySet() {
     }
 
     private final ETLogger log;
-    private final Gson gson = new Gson();
+    private final Gson gson;
 
     public static final String DEFAULT_VENDORDEPS_FOLDER_NAME = "vendordeps";
     public static final String NATIVEUTILS_VENDOR_FOLDER_PROPERTY = "nativeutils.vendordep.folder.path";
@@ -69,6 +71,10 @@ public WPIJavaVendorDepsExtension getJavaVendor() {
 
     @Inject
     public WPIVendorDepsExtension(Project project) {
+        GsonBuilder builder = new GsonBuilder();
+        builder.setPrettyPrinting();
+        builder.registerTypeAdapterFactory(OptionalTypeAdapter.FACTORY);
+        gson = builder.create();
 
         frcYear = project.getObjects().property(String.class);
         frcHome = project.getObjects().directoryProperty();
@@ -315,7 +321,7 @@ public static class JsonDependency {
         public VendorDependency[] conflictsWith;
         public String[] mavenUrls;
         public String[] extraGroupIds;
-        public String jsonUrl;
+        public Optional<String> jsonUrl;
         public String fileName;
         public String frcYear;
         public JavaArtifact[] javaDependencies;