Enable Clang Tidy (#1586)

Summary:
X-link: https://github.com/facebook/litho/pull/976

Pull Request resolved: https://github.com/facebook/yoga/pull/1586

X-link: https://github.com/facebook/react-native/pull/43299

Add the React Clang Tidy config to Yoga, run the auto fixes, and make some manual mechanical tweaks.

Notably, the automatic changes to the infra for generating a Yoga tree from JSON capture make it 70% faster.

Before:
{F1463947076}

After:
{F1463946802}

This also cleans up all the no-op shallow const parameters in headers.

{F1463943386}

Not all checks are available in all environments, but that is okay, as Clang Tidy will gracefully skip them.

Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D54461054

fbshipit-source-id: dbd2d9ce51afd3174d1f2c6d439fa7d08baff46f

java/jni/corefunctions.cpp

@@ -12,9 +12,9 @@
 namespace facebook::yoga::vanillajni {
 
 namespace {
-JavaVM* globalVm = NULL;
+JavaVM* globalVm = nullptr;
 struct JavaVMInitializer {
-  JavaVMInitializer(JavaVM* vm) {
+  explicit JavaVMInitializer(JavaVM* vm) {
     if (!vm) {
       logErrorMessageAndDie(
           "You cannot pass a NULL JavaVM to ensureInitialized");
@@ -27,7 +27,7 @@ struct JavaVMInitializer {
 jint ensureInitialized(JNIEnv** env, JavaVM* vm) {
   static JavaVMInitializer init(vm);
 
-  if (!env) {
+  if (env == nullptr) {
     logErrorMessageAndDie(
         "Need to pass a valid JNIEnv pointer to vanillajni initialization "
         "routine");
@@ -43,7 +43,7 @@ jint ensureInitialized(JNIEnv** env, JavaVM* vm) {
 
 // TODO why we need JNIEXPORT for getCurrentEnv ?
 JNIEXPORT JNIEnv* getCurrentEnv() {
-  JNIEnv* env;
+  JNIEnv* env = nullptr;
   jint ret = globalVm->GetEnv((void**)&env, JNI_VERSION_1_6);
   if (ret != JNI_OK) {
     logErrorMessageAndDie(
@@ -68,7 +68,7 @@ void assertNoPendingJniException(JNIEnv* env) {
   }
 
   auto throwable = env->ExceptionOccurred();
-  if (!throwable) {
+  if (throwable == nullptr) {
     logErrorMessageAndDie("Unable to get pending JNI exception.");
   }
   env->ExceptionClear();