fix: do not emit afterCartUpdate unless surcharges are updated

imports/plugins/core/discounts/server/no-meteor/startup.js

@@ -1,3 +1,4 @@
+import Logger from "@reactioncommerce/logger";
 import appEvents from "/imports/node-app/core/util/appEvents";
 import getDiscountsTotalForCart from "/imports/plugins/core/discounts/server/no-meteor/util/getDiscountsTotalForCart";
 
@@ -14,6 +15,7 @@ export default function startup(context) {
     if (!cart) {
       throw new Error("afterCartUpdate hook run with no cart argument");
     }
+    Logger.debug("Handling afterCartUpdate: discounts");
 
     const cartId = cart._id;
     const { total: discount } = await getDiscountsTotalForCart(context, cartId);

imports/plugins/core/shipping/server/no-meteor/startup.js

@@ -1,3 +1,4 @@
+import Logger from "@reactioncommerce/logger";
 import Random from "@reactioncommerce/random";
 import ReactionError from "@reactioncommerce/reaction-error";
 
@@ -28,6 +29,7 @@ export default function startup({ appEvents, collections }) {
     if (!updatedCart) {
       throw new Error("afterCartUpdate hook run with no cart argument");
     }
+    Logger.debug("Handling afterCartUpdate: shipping");
 
     // Every time the cart is updated, create any missing fulfillment groups as necessary.
     // We need one group per type per shop, containing only the items from that shop.

imports/plugins/core/taxes/server/no-meteor/startup.js

@@ -1,4 +1,5 @@
 import { isEqual } from "lodash";
+import Logger from "@reactioncommerce/logger";
 import getUpdatedCartItems from "./util/getUpdatedCartItems";
 
 const EMITTED_BY_NAME = "TAXES_CORE_PLUGIN";
@@ -18,6 +19,7 @@ export default function startup(context) {
   // have changed.
   appEvents.on("afterCartUpdate", async ({ cart }, { emittedBy } = {}) => {
     if (emittedBy === EMITTED_BY_NAME) return; // short circuit infinite loops
+    Logger.debug("Handling afterCartUpdate: taxes");
 
     const { cartItems, taxSummary } = await getUpdatedCartItems(context, cart);
 

imports/plugins/included/surcharges/server/no-meteor/startup.js

@@ -1,3 +1,5 @@
+import { isEqual } from "lodash";
+import Logger from "@reactioncommerce/logger";
 import xformCartGroupToCommonOrder from "/imports/plugins/core/cart/server/no-meteor/util/xformCartGroupToCommonOrder";
 import collectionIndex from "/imports/utils/collectionIndex";
 import getSurcharges from "./getSurcharges";
@@ -20,8 +22,9 @@ export default function startup(context) {
   // Update the cart to include surcharges, if applicable
   appEvents.on("afterCartUpdate", async ({ cart }, { emittedBy } = {}) => {
     if (emittedBy === EMITTED_BY_NAME) return; // short circuit infinite loops
+    Logger.debug("Handling afterCartUpdate: surcharges");
 
-    const { shipping } = cart;
+    const { surcharges, shipping } = cart;
     const cartSurcharges = [];
 
     // Merge surcharges from each shipping group
@@ -35,6 +38,13 @@ export default function startup(context) {
       });
     }
 
+    // To avoid infinite looping among various `afterCartUpdate` handlers that also
+    // update cart and emit a subsequent `afterCartUpdate`, we need to be sure we
+    // do not do the update or emit the event unless we truly need to update something.
+    const previousSurcharges = (surcharges || []).map((appliedSurcharge) => ({ ...appliedSurcharge, _id: null }));
+    const nextSurcharges = cartSurcharges.map((appliedSurcharge) => ({ ...appliedSurcharge, _id: null }));
+    if (isEqual(previousSurcharges, nextSurcharges)) return;
+
     const { value: updatedCart } = await Cart.findOneAndUpdate({ _id: cart._id }, {
       $set: {
         surcharges: cartSurcharges
@@ -44,6 +54,6 @@ export default function startup(context) {
       returnOriginal: false
     });
 
-    appEvents.emit("afterCartUpdate", { cart: updatedCart }, { emittedBy: EMITTED_BY_NAME });
+    appEvents.emit("afterCartUpdate", { cart: updatedCart, updatedBy: null }, { emittedBy: EMITTED_BY_NAME });
   });
 }