iOS Buck: Create CoreModules sub-target

Summary: Right now the entire RN core code lives inside one giant internal Buck target. This makes it hard to refactor the infra and to roll out TurboModules. For now, create a baseline for how RN core dir can be structured.

Reviewed By: PeteTheHeat

Differential Revision: D16001260

fbshipit-source-id: bba947e2fb75576a2e1f3f4c816575f1157dcb03

Author: fkgozali

.gitignore

@@ -72,7 +72,10 @@ RNTester/build
 
 # Libs that shouldn't have Xcode project
 /Libraries/FBLazyVector/**/*.xcodeproj
+/Libraries/FBReactNativeSpec/**/*.xcodeproj
 /Libraries/RCTRequired/**/*.xcodeproj
+/React/CoreModules/**/*.xcodeproj
+/packages/react-native-codegen/**/*.xcodeproj
 
 # CocoaPods
 /template/ios/Pods/

React/Base/RCTVersion.h

@@ -8,9 +8,11 @@
 
 #import <Foundation/Foundation.h>
 
-extern NSString* const RCTVersionMajor;
-extern NSString* const RCTVersionMinor;
-extern NSString* const RCTVersionPatch;
-extern NSString* const RCTVersionPrerelease;
+#import <React/RCTDefines.h>
 
-extern NSDictionary* RCTGetReactNativeVersion(void);
+RCT_EXTERN NSString* const RCTVersionMajor;
+RCT_EXTERN NSString* const RCTVersionMinor;
+RCT_EXTERN NSString* const RCTVersionPatch;
+RCT_EXTERN NSString* const RCTVersionPrerelease;
+
+RCT_EXTERN NSDictionary* RCTGetReactNativeVersion(void);

React/CoreModules/BUCK

@@ -0,0 +1,56 @@
+load("@fbsource//tools/build_defs/apple:flag_defs.bzl", "OBJC_ARC_PREPROCESSOR_FLAGS", "get_debug_preprocessor_flags", "get_fbobjc_enable_exception_lang_compiler_flags_DEPRECATED")
+load("//tools/build_defs/oss:rn_defs.bzl", "rn_debug_flags", "rn_apple_library", "subdir_glob")
+
+rn_apple_library(
+    name = "CoreModulesApple",
+    srcs = glob(
+        [
+            "**/*.m",
+            "**/*.mm",
+        ],
+    ),
+    headers = glob(
+        [
+            "**/*.h",
+        ],
+    ),
+    header_namespace = "",
+    exported_headers = subdir_glob(
+        [
+            (
+                "",
+                "*.h",
+            ),
+        ],
+        prefix = "React",
+    ),
+    compiler_flags = [
+        "-Wno-error=unguarded-availability-new",
+        "-Wno-unknown-warning-option",
+    ],
+    contacts = ["oncall+react_native@xmail.facebook.com"],
+    exported_linker_flags = [
+        "-weak_framework",
+        "UserNotifications",
+        "-weak_framework",
+        "WebKit",
+    ],
+    exported_preprocessor_flags = rn_debug_flags(),
+    frameworks = [
+        "Foundation",
+        "UIKit",
+    ],
+    labels = ["depslint_never_add"],
+    lang_compiler_flags = get_fbobjc_enable_exception_lang_compiler_flags_DEPRECATED(),
+    link_whole = True,
+    platform_preprocessor_flags = [(
+        "linux",
+        ["-D PIC_MODIFIER=@PLT"],
+    )],
+    preprocessor_flags = OBJC_ARC_PREPROCESSOR_FLAGS + get_debug_preprocessor_flags() + rn_debug_flags(),
+    visibility = ["PUBLIC"],
+    exported_deps = [
+        "fbsource//xplat/js/react-native-github:ReactInternalApple",
+        "fbsource//xplat/js/react-native-github/Libraries/FBReactNativeSpec:FBReactNativeSpecApple",
+    ],
+)

React/Base/RCTPlatform.h React/CoreModules/RCTPlatform.hReact/Base/RCTPlatform.h renamed to React/CoreModules/RCTPlatform.h

@@ -9,8 +9,8 @@
 
 #import <UIKit/UIKit.h>
 
-#import "RCTUtils.h"
-#import "RCTVersion.h"
+#import <React/RCTUtils.h>
+#import <React/RCTVersion.h>
 
 static NSString *interfaceIdiom(UIUserInterfaceIdiom idiom) {
   switch(idiom) {

React/Base/RCTPlatform.m React/CoreModules/RCTPlatform.mmReact/Base/RCTPlatform.m renamed to React/CoreModules/RCTPlatform.mm

@@ -100,6 +100,12 @@ def react_native_dep(path):
 def react_native_xplat_dep(path):
     return "//ReactCommon/" + path
 
+def rn_debug_flags():
+    return []
+
+def rn_feature_flags():
+    return []
+
 # React property preprocessor
 def rn_android_library(name, deps = [], plugins = [], *args, **kwargs):
     if react_native_target(