Codegen Android: allow generating Fabric Java component files during build time

Summary:
This commit:
* Generate Fabric component Java files along side Java NativeModule specs, when `USE_FABRIC=1` is set
* Adjust the component codegen to place output files in a subdir based on package name
* Adjust existing Buck targets to filter the right nativemodule vs component java files (this avoids duplicated symbols)
* Compiles the Java output during build time on RNTester/ReactAndroid (Gradle)

Not in this commit:
* Fabric C++ files
* Removing checked-in generated component files.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D25416614

fbshipit-source-id: fd670ead2198c9b5a65812c692b7aed9f3d7cd58

packages/react-native-codegen/src/generators/components/GeneratePropsJavaInterface.js

@@ -35,7 +35,7 @@ const template = `/**
 * ${'@'}generated by codegen project: GeneratePropsJavaInterface.js
 */
 
-package com.facebook.react.viewmanagers;
+package ::_PACKAGE_NAME_::;
 
 ::_IMPORTS_::
 
@@ -215,6 +215,12 @@ module.exports = {
     moduleSpecName: string,
     packageName?: string,
   ): FilesOutput {
+    // TODO: This doesn't support custom package name yet.
+    // TODO: But it customizes the name here temporarily to prepare for Fabric RNTester support.
+    const normalizedPackageName =
+      packageName != null ? packageName : 'com.facebook.react.viewmanagers';
+    const outputDir = `java/${normalizedPackageName.replace(/\./g, '/')}`;
+
     const files = new Map();
     Object.keys(schema.modules).forEach(moduleName => {
       const module = schema.modules[moduleName];
@@ -240,7 +246,6 @@ module.exports = {
         .forEach(componentName => {
           const component = components[componentName];
           const className = getInterfaceJavaClassName(componentName);
-          const fileName = `${className}.java`;
 
           const imports = getImports(component, 'interface');
           const propsString = generatePropsString(component, imports);
@@ -257,6 +262,7 @@ module.exports = {
                 .sort()
                 .join('\n'),
             )
+            .replace(/::_PACKAGE_NAME_::/g, normalizedPackageName)
             .replace(/::_CLASSNAME_::/g, className)
             .replace('::_EXTEND_CLASSES_::', extendString)
             .replace(
@@ -265,7 +271,7 @@ module.exports = {
             )
             .replace('::_COMMAND_HANDLERS_::', commandsString);
 
-          files.set(fileName, replacedTemplate);
+          files.set(`${outputDir}/${className}.java`, replacedTemplate);
         });
     });