Generate FBReactNativeSpec ObjC++ source files using CocoaPods

Summary:
Move FBReactNativeSpec codegen invocation to shared `react_native_pods.rb` script and trigger codegen to run as part of `pod install` in both RNTester as well as React Native for iOS projects.

These files need to be generated before CocoaPods generates the Pods project, so the codegen is invoked as part of a `pre_install` hook during `pod install`.

The codegen hook can now take optional paths to allow it to run within different contexts (as part of a `react-native` repo checkout with access to the codegen source, or as part of a React Native iOS project that depends on the `react-native-codegen` npm package).

## Motivation

The FBReactNativeSpec ObjC++ source files (FBReactNativeSpec.h and FBReactNativeSpec-generated.mm) can be generated on demand from the native module specs in `Libraries/` using `react-native-codegen`. They can therefore be removed from the repository, but before we do so, we must ensure they get generated when a React Native iOS workspace is created or updated.

Invoking the codegen as part of the `pod install` step that creates a React Native iOS Xcode workspace ensures the specs are available in the following scenarios:
* Whenever a new React Native iOS project is created. The `react-native init` command invokes `pod install`.
* Whenever a React Native iOS project is upgraded. The `react-native upgrade` command invokes `pod install` as well.
* For contributors to the open source project running the RNTester application, the codegen will be invoked when the RNTester workspace is generated by CocoaPods using `pod install` in `packages/rn-tester`.

In any other case, the codegen can still be invoked directly via `scripts/generate-native-modules-specs.sh`.

> **Note:**
> The codegen will only process native modules in React Native's own Libraries directory.

Changelog:
[iOS][Changed] - Generate FBReactNativeSpec ObjC++ source files using CocoaPods.

Reviewed By: fkgozali

Differential Revision: D24348111

fbshipit-source-id: d62ae5c6f8ce6358bf96a2801c3cdb3d94dd868d

Author: hramos

package.json

@@ -37,6 +37,7 @@
     "README.md",
     "rn-get-polyfills.js",
     "scripts/compose-source-maps.js",
+    "scripts/generate-native-modules-specs-cli.js",
     "scripts/ios-configure-glog.sh",
     "scripts/launchPackager.bat",
     "scripts/launchPackager.command",

packages/rn-tester/Podfile

@@ -56,13 +56,13 @@ def frameworks_pre_install(installer)
   end
 end
 
-def codegen_pre_install(installer)
-  system("../../scripts/generate-native-modules-specs.sh")
-end
-
 pre_install do |installer|
   frameworks_pre_install(installer) if ENV['USE_FRAMEWORKS'] == '1'
-  codegen_pre_install(installer) if ENV['USE_CODEGEN'] == '1'
+  if ENV['USE_CODEGEN'] != '0'
+    prefix_path = "../.."
+    codegen_path = "../../packages/react-native-codegen"
+    codegen_pre_install(installer, {path:prefix_path, codegen_path:codegen_path})
+  end
 end
 
 post_install do |installer|

packages/rn-tester/Podfile.lock

@@ -528,6 +528,6 @@ SPEC CHECKSUMS:
   Yoga: 69ef0b2bba5387523f793957a9f80dbd61e89631
   YogaKit: f782866e155069a2cca2517aafea43200b01fd5a
 
-PODFILE CHECKSUM: c38c19657f5aaa2d604f5f4c607f030b60452997
+PODFILE CHECKSUM: e8fcdfe0cd22ad16c23d87ada51a7afb492b2ff1
 
 COCOAPODS: 1.9.3

scripts/generate-native-modules-specs-cli.js

@@ -9,7 +9,16 @@
 
 'use strict';
 
-const RNCodegen = require('../packages/react-native-codegen/lib/generators/RNCodegen.js');
+let RNCodegen;
+try {
+  RNCodegen = require('react-native-codegen/lib/generators/RNCodegen.js');
+} catch (e) {
+  RNCodegen = require('../packages/react-native-codegen/lib/generators/RNCodegen.js');
+  if (!RNCodegen) {
+    throw 'RNCodegen not found.';
+  }
+}
+
 const fs = require('fs');
 const mkdirp = require('mkdirp');
 const os = require('os');

scripts/react_native_pods.rb

@@ -109,3 +109,17 @@ def flipper_post_install(installer)
     end
   end
 end
+
+# Pre Install processing for Native Modules
+def codegen_pre_install(installer, options={})
+  prefix = options[:path] ||= "../node_modules/react-native"
+  codegen_path = options[:codegen_path] ||= "../node_modules/react-native-codegen"
+
+  Dir.mktmpdir do |dir|
+    native_module_spec_name = "FBReactNativeSpec"
+    schema_file = dir + "/schema-#{native_module_spec_name}.json"
+    srcs_dir = "#{prefix}/Libraries"
+    schema_generated = system("node #{codegen_path}/lib/cli/combine/combine-js-to-schema-cli.js #{schema_file} #{srcs_dir}")
+    specs_generated = system("node #{prefix}/scripts/generate-native-modules-specs-cli.js ios #{schema_file} #{srcs_dir}/#{native_module_spec_name}/#{native_module_spec_name}")
+  end
+end

template/ios/Podfile

@@ -13,6 +13,10 @@ target 'HelloWorld' do
     # Pods for testing
   end
 
+  pre_install do |installer|
+    codegen_pre_install(installer)
+  end
+
   # Enables Flipper.
   #
   # Note that if you have use_frameworks! enabled, Flipper will not work and

template/package.json

@@ -21,7 +21,8 @@
     "eslint": "^6.5.1",
     "jest": "^25.1.0",
     "metro-react-native-babel-preset": "^0.63.0",
-    "react-test-renderer": "16.13.1"
+    "react-test-renderer": "16.13.1",
+    "react-native-codegen": "0.0.4"
   },
   "jest": {
     "preset": "react-native"