feat: add warning to set functions when value is not a string

* feat: add warning for non-string values

Author: jkossek

lib/AsyncStorage.js

@@ -52,6 +52,14 @@ type MultiRequest = {|
   reject: ?(error?: any) => void,
 |};
 
+function checkValueTypeNotString(value: any, usedKey: string) {
+  if (typeof value !== 'string') {
+    console.warn(
+      `[AsyncStorage] The value for key "${usedKey}" is not a string. This can lead to unexpected behavior/errors. Consider stringifying it.`,
+    );
+  }
+}
+
 /**
  * `AsyncStorage` is a simple, unencrypted, asynchronous, persistent, key-value
  * storage system that is global to the app.  It should be used instead of
@@ -100,6 +108,7 @@ const AsyncStorage = {
   ): Promise<null> {
     return new Promise((resolve, reject) => {
       RCTAsyncStorage.multiSet([[key, value]], function(errors) {
+        checkValueTypeNotString(value, key);
         const errs = convertErrors(errors);
         callback && callback(errs && errs[0]);
         if (errs) {
@@ -301,6 +310,10 @@ const AsyncStorage = {
     callback?: ?(errors: ?$ReadOnlyArray<?Error>) => void,
   ): Promise<null> {
     return new Promise((resolve, reject) => {
+      keyValuePairs.forEach(([key, value]) => {
+        checkValueTypeNotString(value, key);
+      });
+
       RCTAsyncStorage.multiSet(keyValuePairs, function(errors) {
         const error = convertErrors(errors);
         callback && callback(error);