Codegen: JavaGenerator [2] - parse JSON schema into Java typed representation

Summary:
This parses the output JSON schema into Java Type's, without any alias resolution. Some parts of the schema have incomplete information, hence a bunch of TODOs in the code expressing the issues.

Notes:
* The type structure here could be implemented in other codegen generators as well (including the RNCodegen.js' generators) for better type safety and correctness. With this exercise, I was able to catch a few issues mentioned above.
* This commit does not produce any Java code with JavaPoet yet, just parsing the schema.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D23152891

fbshipit-source-id: 9f774dd98975f7202d3faf11c3fbfb83d4c97f5a

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/build.gradle

@@ -20,6 +20,7 @@ gradlePlugin {
 
 dependencies {
     implementation 'com.android.tools.build:gradle:3.5.3'
+    implementation 'com.google.code.gson:gson:2.8.6'
     implementation 'com.google.guava:guava:29.0-jre'
     implementation 'com.squareup:javapoet:1.13.0'
 }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/JavaGenerator.java

@@ -11,6 +11,7 @@ import com.squareup.javapoet.JavaFile;
 import com.squareup.javapoet.MethodSpec;
 import com.squareup.javapoet.TypeSpec;
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import javax.lang.model.element.Modifier;
 
@@ -26,7 +27,7 @@ public final class JavaGenerator {
     mOutputDir = outputDir;
   }
 
-  public void build() throws IOException {
+  public void build() throws FileNotFoundException, IOException {
     final MethodSpec main =
         MethodSpec.methodBuilder("main")
             .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
@@ -43,8 +44,6 @@ public final class JavaGenerator {
 
     final JavaFile javaFile = JavaFile.builder(mJavaPackageName, helloWorld).build();
 
-    System.out.println(javaFile.toString());
-
     javaFile.writeTo(mOutputDir);
   }
 }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/SchemaJsonParser.java

@@ -0,0 +1,250 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.codegen.generator;
+
+import com.facebook.react.codegen.generator.model.AliasType;
+import com.facebook.react.codegen.generator.model.AnyType;
+import com.facebook.react.codegen.generator.model.ArrayType;
+import com.facebook.react.codegen.generator.model.BooleanType;
+import com.facebook.react.codegen.generator.model.DoubleType;
+import com.facebook.react.codegen.generator.model.FloatType;
+import com.facebook.react.codegen.generator.model.FunctionType;
+import com.facebook.react.codegen.generator.model.GenericObjectType;
+import com.facebook.react.codegen.generator.model.Int32Type;
+import com.facebook.react.codegen.generator.model.NativeModuleType;
+import com.facebook.react.codegen.generator.model.NullableType;
+import com.facebook.react.codegen.generator.model.NumberType;
+import com.facebook.react.codegen.generator.model.ObjectType;
+import com.facebook.react.codegen.generator.model.PromiseType;
+import com.facebook.react.codegen.generator.model.RawSchema;
+import com.facebook.react.codegen.generator.model.ReservedFunctionValueType;
+import com.facebook.react.codegen.generator.model.StringType;
+import com.facebook.react.codegen.generator.model.Type;
+import com.facebook.react.codegen.generator.model.TypeId;
+import com.facebook.react.codegen.generator.model.VoidType;
+import com.google.common.collect.ImmutableList;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public final class SchemaJsonParser {
+
+  public static RawSchema parse(final File schemaFile) throws FileNotFoundException, IOException {
+    final JsonParser parser = new JsonParser();
+    final JsonElement rootElement = parser.parse(new FileReader(schemaFile));
+
+    final Map<String, List<NativeModuleType>> collection = new HashMap<>();
+
+    if (rootElement.isJsonObject()) {
+      final JsonObject root = rootElement.getAsJsonObject();
+      final JsonObject modules = root.getAsJsonObject("modules");
+      modules
+          .entrySet()
+          .forEach(
+              entry -> {
+                final String jsModuleName = entry.getKey();
+                final JsonObject jsModule = entry.getValue().getAsJsonObject();
+                final JsonObject nativeModules = jsModule.getAsJsonObject("nativeModules");
+                if (nativeModules == null) {
+                  // TODO: Handle components-related sections.
+                  return;
+                }
+
+                collection.put(
+                    jsModuleName,
+                    nativeModules.entrySet().stream()
+                        .map(
+                            nativeModuleEntry -> {
+                              return parseNativeModule(
+                                  TypeId.of(jsModuleName, nativeModuleEntry.getKey()),
+                                  nativeModuleEntry.getValue().getAsJsonObject());
+                            })
+                        .collect(Collectors.toList()));
+              });
+    }
+
+    return new RawSchema(collection);
+  }
+
+  private static NativeModuleType parseNativeModule(final TypeId typeId, final JsonObject json) {
+    final JsonObject aliases = json.getAsJsonObject("aliases");
+    final JsonArray properties = json.getAsJsonArray("properties");
+
+    // TODO: parse aliases
+
+    ImmutableList.Builder<NativeModuleType.Property> methods = new ImmutableList.Builder<>();
+    properties.forEach(
+        p -> {
+          final JsonObject node = p.getAsJsonObject();
+          final String name = node.has("name") ? node.get("name").getAsString() : null;
+          final JsonObject typeAnnotation = node.getAsJsonObject("typeAnnotation");
+          // TODO (T71845349): "optional" field shouldn't be part of the Function's typeAnnotation.
+          final boolean optional = typeAnnotation.get("optional").getAsBoolean();
+          final TypeId propertyTypeId = TypeId.of(typeId.moduleName, name);
+          methods.add(
+              new NativeModuleType.Property(
+                  name, parseTypeAnnotation(propertyTypeId, typeAnnotation), optional));
+        });
+
+    return new NativeModuleType(typeId, methods.build());
+  }
+
+  // Parse type information from a JSON "typeAnnotation" node.
+  private static Type parseTypeAnnotation(final TypeId typeId, final JsonObject typeAnnotation)
+      throws IllegalStateException {
+    final String type = typeAnnotation.get("type").getAsString();
+    // TODO (T71824250): Support NullableTypeAnnotation in the schema instead of a field here.
+    final boolean nullable =
+        typeAnnotation.has("nullable") ? typeAnnotation.get("nullable").getAsBoolean() : false;
+
+    Type parsedType = null;
+
+    switch (type) {
+      case AliasType.TYPE_NAME:
+        // TODO
+        parsedType = new AliasType(typeId, typeId);
+        break;
+      case AnyType.TYPE_NAME:
+        parsedType = new AnyType(typeId);
+        break;
+      case ArrayType.TYPE_NAME:
+        parsedType = parseArrayTypeAnnotation(typeId, typeAnnotation);
+        break;
+      case BooleanType.TYPE_NAME:
+        parsedType = new BooleanType(typeId);
+        break;
+      case DoubleType.TYPE_NAME:
+        parsedType = new DoubleType(typeId);
+        break;
+      case FloatType.TYPE_NAME:
+        parsedType = new FloatType(typeId);
+        break;
+      case FunctionType.TYPE_NAME:
+        parsedType = parseFunctionTypeAnnotation(typeId, typeAnnotation);
+        break;
+      case GenericObjectType.TYPE_NAME:
+        parsedType = new GenericObjectType(typeId);
+        break;
+      case Int32Type.TYPE_NAME:
+        parsedType = new Int32Type(typeId);
+        break;
+      case NumberType.TYPE_NAME:
+        parsedType = new NumberType(typeId);
+        break;
+      case ObjectType.TYPE_NAME:
+        parsedType = parseObjectTypeAnnotation(typeId, typeAnnotation);
+        break;
+      case PromiseType.TYPE_NAME:
+        parsedType = new PromiseType(typeId);
+        break;
+      case ReservedFunctionValueType.TYPE_NAME:
+        // TODO
+        parsedType =
+            new ReservedFunctionValueType(typeId, ReservedFunctionValueType.ReservedName.RootTag);
+      case StringType.TYPE_NAME:
+        parsedType = new StringType(typeId);
+        break;
+      case VoidType.TYPE_NAME:
+        return VoidType.VOID;
+      default:
+        throw new IllegalStateException("Found invalid type annotation: " + type);
+    }
+
+    return maybeCreateNullableType(nullable, parsedType);
+  }
+
+  private static Type parseArrayTypeAnnotation(
+      final TypeId typeId, final JsonObject typeAnnotation) {
+    final JsonObject elementTypeAnnotation = typeAnnotation.getAsJsonObject("elementType");
+    // TODO (T71847026): Some array types are missing elementType annotation.
+    final Type elementType =
+        elementTypeAnnotation != null
+            ? parseTypeAnnotation(
+                TypeId.of(
+                    typeId.moduleName,
+                    elementTypeAnnotation.has("name")
+                        ? elementTypeAnnotation.get("name").getAsString()
+                        : null),
+                elementTypeAnnotation)
+            : new AnyType(TypeId.of(typeId.moduleName));
+
+    return new ArrayType(typeId, elementType);
+  }
+
+  private static Type parseFunctionTypeAnnotation(
+      final TypeId typeId, final JsonObject typeAnnotation) {
+    final JsonArray params = typeAnnotation.getAsJsonArray("params");
+
+    ImmutableList.Builder<FunctionType.ArgumentType> paramsList = new ImmutableList.Builder<>();
+
+    // TODO (T71846321): Some functions are missing params specification.
+    if (params != null) {
+      params.forEach(
+          p -> {
+            final JsonObject node = p.getAsJsonObject();
+            final String name = node.has("name") ? node.get("name").getAsString() : null;
+            paramsList.add(
+                FunctionType.createArgument(
+                    name,
+                    parseTypeAnnotation(
+                        TypeId.of(typeId.moduleName, name),
+                        node.getAsJsonObject("typeAnnotation"))));
+          });
+    }
+
+    // TODO (T71846321): Some functions are missing a return type.
+    final JsonObject returnTypeAnnotation = typeAnnotation.getAsJsonObject("returnTypeAnnotation");
+    final Type returnType =
+        returnTypeAnnotation != null
+            ? parseTypeAnnotation(TypeId.of(typeId.moduleName), returnTypeAnnotation)
+            : VoidType.VOID;
+
+    return new FunctionType(typeId, paramsList.build(), returnType);
+  }
+
+  private static Type parseObjectTypeAnnotation(
+      final TypeId typeId, final JsonObject typeAnnotation) {
+    final JsonArray properties = typeAnnotation.getAsJsonArray("properties");
+
+    ImmutableList.Builder<ObjectType.Property> propertiesList = new ImmutableList.Builder<>();
+    properties.forEach(
+        p -> {
+          final JsonObject node = p.getAsJsonObject();
+          final String name = node.has("name") ? node.get("name").getAsString() : null;
+          final boolean optional = node.get("optional").getAsBoolean();
+          final JsonObject propertyTypeAnnotation = node.getAsJsonObject("typeAnnotation");
+          final TypeId propertyTypeId = TypeId.of(typeId.moduleName, name);
+
+          // TODO (T67898313): Some object properties are missing typeAnnotation.
+          final Type propertyType =
+              propertyTypeAnnotation != null
+                  ? parseTypeAnnotation(propertyTypeId, propertyTypeAnnotation)
+                  : new AnyType(propertyTypeId);
+
+          propertiesList.add(new ObjectType.Property(name, propertyType, optional));
+        });
+
+    return new ObjectType(typeId, propertiesList.build());
+  }
+
+  private static Type maybeCreateNullableType(final boolean nullable, final Type original) {
+    if (!nullable || original instanceof VoidType) {
+      return original;
+    }
+    return new NullableType(TypeId.of(original.getTypeId()), original);
+  }
+}

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/AliasType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class AliasType extends Type {
+  public static final String TYPE_NAME = "TypeAliasTypeAnnotation";
 
   public final TypeId referredTypeId;
 

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/AnyType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class AnyType extends Type {
+  public static final String TYPE_NAME = "AnyTypeAnnotation";
 
   public AnyType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/ArrayType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class ArrayType extends Type {
+  public static final String TYPE_NAME = "ArrayTypeAnnotation";
 
   public final Type elementType;
 

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/BooleanType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class BooleanType extends Type {
+  public static final String TYPE_NAME = "BooleanTypeAnnotation";
 
   public BooleanType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/DoubleType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class DoubleType extends NumberType {
+  public static final String TYPE_NAME = "DoubleTypeAnnotation";
 
   public DoubleType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/FloatType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class FloatType extends NumberType {
+  public static final String TYPE_NAME = "FloatTypeAnnotation";
 
   public FloatType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/FunctionType.java

@@ -12,11 +12,14 @@ import java.util.List;
 import java.util.Objects;
 
 public final class FunctionType extends Type {
+  public static final String TYPE_NAME = "FunctionTypeAnnotation";
 
   public static class ArgumentType {
     public final String name;
     public final Type type;
 
+    // Note: Function argument is not optional.
+    // TODO (T71926678): Revisit if optional should be supported.
     private ArgumentType(String name, Type type) {
       this.name = name;
       this.type = type;
@@ -39,19 +42,29 @@ public final class FunctionType extends Type {
     public int hashCode() {
       return Objects.hash(name, type);
     }
+
+    @Override
+    public String toString() {
+      return name + ": " + type;
+    }
+  }
+
+  public static ArgumentType createArgument(String name, Type type) {
+    return new ArgumentType(name, type);
   }
 
   public final List<ArgumentType> parameters;
   public final Type returnType;
 
-  public FunctionType(final TypeId typeId, List<ArgumentType> parameters, Type returnType) {
+  public FunctionType(
+      final TypeId typeId, final List<ArgumentType> parameters, final Type returnType) {
     super(typeId);
     this.parameters = Collections.unmodifiableList(parameters);
     this.returnType = returnType;
   }
 
   @Override
-  public boolean equals(Object o) {
+  public boolean equals(final Object o) {
     if (this == o) {
       return true;
     }
@@ -59,7 +72,7 @@ public final class FunctionType extends Type {
       return false;
     }
 
-    FunctionType that = (FunctionType) o;
+    final FunctionType that = (FunctionType) o;
     return Objects.equals(this.parameters, that.parameters)
         && Objects.equals(this.returnType, that.returnType);
   }
@@ -68,4 +81,9 @@ public final class FunctionType extends Type {
   public int hashCode() {
     return Objects.hash(super.hashCode(), parameters, returnType);
   }
+
+  @Override
+  public String toString() {
+    return "(" + returnType + ")" + this.getTypeId() + "(" + parameters + ")";
+  }
 }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/GenericObjectType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class GenericObjectType extends Type {
+  public static final String TYPE_NAME = "GenericObjectTypeAnnotation";
 
   public GenericObjectType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/Int32Type.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class Int32Type extends NumberType {
+  public static final String TYPE_NAME = "Int32TypeAnnotation";
 
   public Int32Type(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/NativeModuleType.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.codegen.generator.model;
+
+import java.util.Collections;
+import java.util.List;
+
+public final class NativeModuleType extends Type {
+  public static String TYPE_NAME = "<NONE>"; // Not an actual type in the schema.
+
+  public final List<Property> properties;
+
+  public static class Property {
+    public final String name;
+    public final FunctionType type;
+    public final boolean optional;
+
+    public Property(final String name, final Type type, final boolean optional) {
+      assertType(type, FunctionType.class);
+      this.name = name;
+      this.type = (FunctionType) type;
+      this.optional = optional;
+    }
+
+    @Override
+    public String toString() {
+      return name + ": " + (this.optional ? "?" : "") + type;
+    }
+  }
+
+  public NativeModuleType(final TypeId typeId, final List<Property> properties) {
+    super(typeId);
+    this.properties = Collections.unmodifiableList(properties);
+  }
+
+  @Override
+  public String toString() {
+    return getTypeId() + " -> " + properties;
+  }
+}

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/NullableType.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.codegen.generator.model;
+
+public final class NullableType extends Type {
+  public static final String TYPE_NAME = "NullableTypeAnnotation";
+
+  public final Type referredType;
+
+  public NullableType(final TypeId typeId, final Type referredType) {
+    super(typeId);
+    this.referredType = referredType;
+  }
+}

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/NumberType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public class NumberType extends Type {
+  public static final String TYPE_NAME = "NumberTypeAnnotation";
 
   public NumberType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/ObjectType.java

@@ -7,26 +7,38 @@
 
 package com.facebook.react.codegen.generator.model;
 
-public final class ObjectType extends Type {
+import java.util.Collections;
+import java.util.List;
 
-  public ObjectType(final TypeId typeId) {
-    super(typeId);
-  }
+public final class ObjectType extends Type {
+  public static final String TYPE_NAME = "ObjectTypeAnnotation";
 
   public static class Property {
-    public final String propertyName;
+    public final String name;
     public final Type type;
     public final boolean optional;
 
-    public Property(String propertyName, Type type, boolean optional) {
-      this.propertyName = propertyName;
+    public Property(String name, Type type, boolean optional) {
+      this.name = name;
       this.type = type;
       this.optional = optional;
     }
 
     @Override
     public String toString() {
-      return propertyName + " " + type;
+      return (optional ? "?" : "") + name + ": " + type;
     }
   }
+
+  public final List<Property> properties;
+
+  public ObjectType(final TypeId typeId, final List<Property> properties) {
+    super(typeId);
+    this.properties = Collections.unmodifiableList(properties);
+  }
+
+  @Override
+  public String toString() {
+    return getTypeId() + " -> " + properties;
+  }
 }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/PromiseType.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.codegen.generator.model;
+
+public final class PromiseType extends Type {
+  public static final String TYPE_NAME = "GenericPromiseTypeAnnotation";
+
+  public PromiseType(final TypeId typeId) {
+    super(typeId);
+  }
+}

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/RawSchema.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react.codegen.generator.model;
+
+import java.util.List;
+import java.util.Map;
+
+/** Represents the parsed JSON schema without any type resolution. */
+public final class RawSchema {
+
+  public final Map<String, List<NativeModuleType>> modules;
+
+  public RawSchema(final Map<String, List<NativeModuleType>> modules) {
+    this.modules = modules;
+  }
+
+  @Override
+  public String toString() {
+    return modules.toString();
+  }
+}

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/ReservedFunctionValueType.java

@@ -8,6 +8,8 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class ReservedFunctionValueType extends Type {
+  public static final String TYPE_NAME = "ReservedFunctionValueTypeAnnotation";
+
   public enum ReservedName {
     RootTag,
   }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/StringType.java

@@ -8,6 +8,7 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class StringType extends Type {
+  public static final String TYPE_NAME = "StringTypeAnnotation";
 
   public StringType(final TypeId typeId) {
     super(typeId);

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/Type.java

@@ -10,8 +10,18 @@ package com.facebook.react.codegen.generator.model;
 import java.util.Objects;
 
 public abstract class Type {
+  public static String TYPE_NAME = "<NONE>";
+
   protected final TypeId mTypeId;
 
+  public static <T extends Type> void assertType(
+      final Type type, final Class<T> expectedTypeClass) {
+    if (!expectedTypeClass.isInstance(type)) {
+      throw new IllegalStateException(
+          "Expected: " + expectedTypeClass.getName() + " but found: " + type.getClass().getName());
+    }
+  }
+
   public Type(final TypeId typeId) {
     mTypeId = typeId;
   }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/TypeId.java

@@ -38,6 +38,10 @@ public final class TypeId {
     return new TypeId(moduleName, typeName);
   }
 
+  public static TypeId of(final TypeId typeId) {
+    return of(typeId.moduleName, typeId.typeName);
+  }
+
   @Override
   public String toString() {
     return String.format(

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/generator/model/VoidType.java

@@ -8,8 +8,10 @@
 package com.facebook.react.codegen.generator.model;
 
 public final class VoidType extends Type {
+  public static final String TYPE_NAME = "VoidTypeAnnotation";
+  public static final VoidType VOID = new VoidType(TypeId.of(""));
 
-  public VoidType(final TypeId typeId) {
+  private VoidType(final TypeId typeId) {
     super(typeId);
   }
 }

packages/react-native-codegen/android/gradlePlugin-build/gradlePlugin/src/main/java/com/facebook/react/codegen/plugin/CodegenPlugin.java

@@ -12,7 +12,7 @@ import com.facebook.react.codegen.generator.JavaGenerator;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import java.io.File;
-import java.io.IOException;
+import org.gradle.api.GradleException;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
@@ -159,8 +159,8 @@ public class CodegenPlugin implements Plugin<Project> {
     final JavaGenerator generator = new JavaGenerator(schemaFile, javaPackageName, outputDir);
     try {
       generator.build();
-    } catch (final IOException e) {
-      // Ignore for now.
+    } catch (final Exception ex) {
+      throw new GradleException("Failed to generate Java from schema.", ex);
     }
   }
 }