Codegen Android: build react-native-codegen via yarn when building from source

Summary:
The Gradle codegen integration requires the JS CLI to be first built via `yarn run build`. This commit puts that logic in a `build.sh` script, then defines a Gradle task to build it.

Changelog: [Internal]

Reviewed By: hramos

Differential Revision: D24556992

fbshipit-source-id: 7092de7c1126edc157b122f4b2243e55f7188846

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

@@ -23,3 +23,24 @@ allprojects {
         jcenter()
     }
 }
+
+// This task is required when using react-native-codegen from source, instead of npm.
+task('buildCodegenCLI', type: Exec) {
+    def codegenRoot = "$projectDir/.."
+
+    inputs.files(
+        file("$codegenRoot/scripts"),
+        file("$codegenRoot/src"),
+        file("$codegenRoot/package.json"),
+        file("$codegenRoot/.babelrc"),
+        file("$codegenRoot/.prettierrc"),
+    )
+
+    def libDir = file("$codegenRoot/lib")
+    libDir.mkdirs()
+    def nodeModulesDir = file("$codegenRoot/node_modules")
+    nodeModulesDir.mkdirs();
+    outputs.dirs(libDir, nodeModulesDir)
+
+    commandLine("$codegenRoot/scripts/oss/build.sh")
+}

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

@@ -50,6 +50,9 @@ public class CodegenPlugin implements Plugin<Project> {
                 return;
               }
 
+              // This is needed when using codegen from source, not from npm.
+              task.dependsOn(":packages:react-native-codegen:android:buildCodegenCLI");
+
               task.doFirst(
                   s -> {
                     generatedSrcDir.delete();

packages/react-native-codegen/scripts/oss/build.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# 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.
+
+# This script assumes yarn is already installed.
+
+THIS_DIR=$(cd -P "$(dirname "$(readlink "${BASH_SOURCE[0]}" || echo "${BASH_SOURCE[0]}")")" && pwd)
+
+set -e
+set -u
+
+pushd "$THIS_DIR/../.." >/dev/null
+
+yarn install 2> >(grep -v '^warning' 1>&2)
+yarn run build
+
+popd >/dev/null

settings.gradle.kts

@@ -15,6 +15,7 @@ pluginManagement {
 
 include(
     ":ReactAndroid",
+    ":packages:react-native-codegen:android",
     ":packages:rn-tester:android:app"
 )