fix ReadableNativeMap.toHashMap() for nested maps and arrays

Summary:
<!--
  Required: Write your motivation here.
  If this PR fixes an issue, type "Fixes #issueNumber" to automatically close the issue when the PR is merged.
-->

Commit https://github.com/facebook/react-native/commit/7891805d22e3fdc821961ff0ccc5c450c3d625c8 broke the previous behavior of `ReadableNativeMap.toHashMap()` for nested maps and arrays. Previously, all nested `ReadableNativeMap`s and `ReadableNativeArray`s were recursively converted to `HashMap`s and `ArrayList`s, but this is lost when only `getLocalMap()` is returned.

<!--
  Required: Write your test plan here. If you changed any code, please provide us with
  clear instructions on how you verified your changes work. Bonus points for screenshots and videos!
-->

Call `ReadableNativeMap.toHashMap()` on a map with values of type `ReadableNativeMap` and `ReadableNativeArray`. Verify the returned hash map has these converted to `HashMap` and `ArrayList`, respectively.

<!--
  Does this PR require a documentation change?
  Create a PR at https://github.com/facebook/react-native-website and add a link to it here.
-->

<!--
  Required.
  Help reviewers and the release process by writing your own release notes. See below for an example.
-->

[ANDROID] [BUGFIX] [ReadableNativeMap] - Fix toHashMap() for nested maps and arrays

<!--
  **INTERNAL and MINOR tagged notes will not be included in the next version's final release notes.**

    CATEGORY
  [----------]      TYPE
  [ CLI      ] [-------------]    LOCATION
  [ DOCS     ] [ BREAKING    ] [-------------]
  [ GENERAL  ] [ BUGFIX      ] [ {Component} ]
  [ INTERNAL ] [ ENHANCEMENT ] [ {Filename}  ]
  [ IOS      ] [ FEATURE     ] [ {Directory} ]   |-----------|
  [ ANDROID  ] [ MINOR       ] [ {Framework} ] - | {Message} |
  [----------] [-------------] [-------------]   |-----------|

 EXAMPLES:

 [IOS] [BREAKING] [FlatList] - Change a thing that breaks other things
 [ANDROID] [BUGFIX] [TextInput] - Did a thing to TextInput
 [CLI] [FEATURE] [local-cli/info/info.js] - CLI easier to do things with
 [DOCS] [BUGFIX] [GettingStarted.md] - Accidentally a thing/word
 [GENERAL] [ENHANCEMENT] [Yoga] - Added new yoga thing/position
 [INTERNAL] [FEATURE] [./scripts] - Added thing to script that nobody will see
-->
Closes https://github.com/facebook/react-native/pull/18455

Reviewed By: kathryngray

Differential Revision: D7347344

Pulled By: mdvacca

fbshipit-source-id: af2bca9dec6c0cb8a7da099b6757434fcc3ac785

ReactAndroid/src/main/java/com/facebook/react/bridge/ReadableNativeMap.java

@@ -13,6 +13,7 @@ import com.facebook.jni.HybridData;
 import com.facebook.proguard.annotations.DoNotStrip;
 
 import java.util.HashMap;
+import java.util.Iterator;
 
 import com.facebook.infer.annotation.Assertions;
 import javax.annotation.Nullable;
@@ -250,7 +251,31 @@ public class ReadableNativeMap extends NativeMap implements ReadableMap {
         }
       return hashMap;
     }
-    return getLocalMap();
+
+    // we can almost just return getLocalMap(), but we need to convert nested arrays and maps to the
+    // correct types first
+    HashMap<String, Object> hashMap = new HashMap<>(getLocalMap());
+    Iterator iterator = hashMap.keySet().iterator();
+
+    while (iterator.hasNext()) {
+      String key = (String) iterator.next();
+      switch (getType(key)) {
+        case Null:
+        case Boolean:
+        case Number:
+        case String:
+          break;
+        case Map:
+          hashMap.put(key, Assertions.assertNotNull(getMap(key)).toHashMap());
+          break;
+        case Array:
+          hashMap.put(key, Assertions.assertNotNull(getArray(key)).toArrayList());
+          break;
+        default:
+          throw new IllegalArgumentException("Could not convert object with key: " + key + ".");
+      }
+    }
+    return hashMap;
   }
 
   /**