mongo: In async wrappers, catch exceptions and reject

Previously, if an exception was thrown in an async method, it would not
be caught, which is unusual in an async method. Instead, catch the
exception and return it as a rejected promise.

packages/minimongo/cursor.js

@@ -520,6 +520,10 @@ export default class Cursor {
 ASYNC_CURSOR_METHODS.forEach(method => {
   const asyncName = getAsyncMethodName(method);
   Cursor.prototype[asyncName] = function(...args) {
-    return Promise.resolve(this[method].apply(this, args));
+    try {
+      return Promise.resolve(this[method].apply(this, args));
+    } catch (error) {
+      return Promise.reject(error);
+    }
   };
 });

packages/mongo/collection.js

@@ -919,6 +919,10 @@ function popCallbackFromArgs(args) {
 ASYNC_COLLECTION_METHODS.forEach(methodName => {
   const methodNameAsync = getAsyncMethodName(methodName);
   Mongo.Collection.prototype[methodNameAsync] = function(...args) {
-    return Promise.resolve(this[methodName](...args));
+    try {
+      return Promise.resolve(this[methodName](...args));
+    } catch (error) {
+      return Promise.reject(error);
+    }
   };
 });

packages/mongo/mongo_driver.js

@@ -945,7 +945,11 @@ Cursor.prototype.count = function () {
 
   const methodNameAsync = getAsyncMethodName(methodName);
   Cursor.prototype[methodNameAsync] = function (...args) {
-    return Promise.resolve(this[methodName](...args));
+    try {
+      return Promise.resolve(this[methodName](...args));
+    } catch (error) {
+      return Promise.reject(error);
+    }
   };
 });