ensure cart totals update when items are removed or quantity changed (https://github.com/woocommerce/woocommerce-blocks/pull/1840)

* ensure cart totals update when items are removed (prototype):
- return complete cart object from DELETE cart/items/:key
- use receiveCart on client to update whole cart including total

* move API endpoint for removing cart items to cart controller:
- returns full cart schema so should be part of cart controller
- is now a POST request with param - not strict REST
- fix up client action to use new API

* move API test for removing cart items (API has moved)

* use correct path for remove API in tests (doh!)

* add extra API test for remove_cart_item with bad key => 404 (experiment)

* experiment: delete test_remove_cart_item, does test_remove_bad_cart_item work?

* reinstate test_remove_cart_item with single valid request

* remove unnecessary newline

* tidy comments in PHP api tests, rerun travis?

* remove test_remove_cart_item which may be causing problems

* reinstate troublesome remove cart item api test (experiment):
- see if this works now travis issue is resolved

* whitespace

* show correct total when changing cart item quantity:
- move update cart item quantity API to cart controller
  - & return full cart response
- update js action to new API route & receive full cart response

* simplify test_remove_cart_item API test - now just tests a valid remove succeeds

* remove test_update_item (API has moved) +
+ experimentally remove test_remove_bad_cart_item
  - testing if cart remove tests interact with each other

* fix tests (🤞) - pass params in body, not as query params

* reinstate test for re-deleting same item

* update API docs - update/delete cart item have moved to /cart

* add response data checks to new cart API tests:
- extra protection against expected 404 "false positives"

* reinstate API test for changing cart item quantity

* fix remove cart item body tests - MIA items return error code, not cart

* fix test - quantity param is int not string

* attempt fix 404ing test_update_item:
- only allow POST, remove trailing `/`
- align array equals for good measure :)

* fix action for update-item - method=POST, now takes body params

* fix response body asserts in test_update_item

* reinstate update_item and delete_item on CartItems controller

* typos + examples in new cart items API docs

* reorder previous cart item docs to minimise diff/churn

* reinstate tabs in docs response example

plugins/woocommerce-blocks/assets/js/data/cart/actions.js

@@ -199,13 +199,13 @@ export function* removeItemFromCart( cartItemKey ) {
 	yield itemQuantityPending( cartItemKey, true );
 
 	try {
-		yield apiFetch( {
+		const cart = yield apiFetch( {
-			path: `/wc/store/cart/items/${ cartItemKey }`,
+			path: `/wc/store/cart/remove-item/?key=${ cartItemKey }`,
-			method: 'DELETE',
+			method: 'POST',
 			cache: 'no-store',
 		} );
 
-		yield receiveRemovedItem( cartItemKey );
+		yield receiveCart( cart );
 	} catch ( error ) {
 		yield receiveError( error );
 	}
@@ -227,15 +227,17 @@ export function* changeCartItemQuantity( cartItemKey, quantity ) {
 	yield itemQuantityPending( cartItemKey, true );
 
 	try {
-		const result = yield apiFetch( {
+		const cart = yield apiFetch( {
-			path: `/wc/store/cart/items/${ cartItemKey }?quantity=${ quantity }`,
+			path: `/wc/store/cart/update-item`,
-			method: 'PUT',
+			method: 'POST',
+			data: {
+				key: cartItemKey,
+				quantity,
+			},
 			cache: 'no-store',
 		} );
 
-		if ( result ) {
+		yield receiveCart( cart );
-			yield receiveCartItem( result );
-		}
 	} catch ( error ) {
 		yield receiveError( error );
 	}

plugins/woocommerce-blocks/src/RestApi/StoreApi/Controllers/Cart.php

@@ -103,6 +103,44 @@ class Cart extends RestController {
 				'schema' => [ $this, 'get_public_item_schema' ],
 			]
 		);
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base . '/remove-item',
+			[
+				[
+					'methods'  => 'POST',
+					'callback' => [ $this, 'remove_cart_item' ],
+					'args'     => [
+						'key' => [
+							'description' => __( 'Unique identifier (key) for the cart item.', 'woo-gutenberg-products-block' ),
+							'type'        => 'string',
+						],
+					],
+				],
+				'schema' => [ $this, 'get_public_item_schema' ],
+			]
+		);
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base . '/update-item',
+			[
+				[
+					'methods'  => 'POST',
+					'callback' => [ $this, 'update_cart_item' ],
+					'args'     => [
+						'key'      => [
+							'description' => __( 'Unique identifier (key) for the cart item to update.', 'woo-gutenberg-products-block' ),
+							'type'        => 'string',
+						],
+						'quantity' => [
+							'description' => __( 'New quantity of the item in the cart.', 'woo-gutenberg-products-block' ),
+							'type'        => 'integer',
+						],
+					],
+				],
+				'schema' => [ $this, 'get_public_item_schema' ],
+			]
+		);
 	}
 
 	/**
@@ -193,6 +231,54 @@ class Cart extends RestController {
 		return $response;
 	}
 
+	/**
+	 * Delete a single cart item.
+	 *
+	 * @param \WP_Rest_Request $request Full data about the request.
+	 * @return \WP_Error|\WP_REST_Response Response object on success, or WP_Error object on failure.
+	 */
+	public function remove_cart_item( $request ) {
+		$controller = new CartController();
+		$cart       = $controller->get_cart_instance();
+		$cart_item  = $controller->get_cart_item( $request['key'] );
+
+		if ( ! $cart_item ) {
+			return new RestError( 'woocommerce_rest_cart_invalid_key', __( 'Cart item does not exist.', 'woo-gutenberg-products-block' ), array( 'status' => 404 ) );
+		}
+
+		$cart->remove_cart_item( $request['key'] );
+
+		$data     = $this->prepare_item_for_response( $cart, $request );
+		$response = rest_ensure_response( $data );
+
+		return $response;
+	}
+
+	/**
+	 * Change quantity for specified cart item.
+	 *
+	 * @param \WP_Rest_Request $request Full data about the request.
+	 * @return \WP_Error|\WP_REST_Response Response object on success, or WP_Error object on failure.
+	 */
+	public function update_cart_item( $request ) {
+		$controller = new CartController();
+		$cart       = $controller->get_cart_instance();
+		$cart_item  = $controller->get_cart_item( $request['key'] );
+
+		if ( ! $cart_item ) {
+			return new RestError( 'woocommerce_rest_cart_invalid_key', __( 'Cart item does not exist.', 'woo-gutenberg-products-block' ), array( 'status' => 404 ) );
+		}
+
+		if ( isset( $request['quantity'] ) ) {
+			$cart->set_quantity( $request['key'], $request['quantity'] );
+		}
+
+		$data     = $this->prepare_item_for_response( $cart, $request );
+		$response = rest_ensure_response( $data );
+
+		return $response;
+	}
+
 	/**
 	 * Cart item schema.
 	 *

plugins/woocommerce-blocks/src/RestApi/StoreApi/README.md

@@ -308,6 +308,8 @@ Example response:
 
 ## Cart API
 
+### Get the cart
+
 ```http
 GET /cart
 ```
@@ -455,6 +457,43 @@ Example response:
 }
 ```
 
+### Edit single cart item
+
+Change the quantity of a cart item.
+
+```http
+PUT /cart/update-item/
+```
+
+| Attribute  | Type    | Required | Description                        |
+| :--------- | :------ | :------: | :--------------------------------- |
+| `key`      | string  |   Yes    | The key of the cart item to edit.  |
+| `quantity` | integer |   Yes    | Quantity of this item in the cart. |
+
+Returns the full cart object (same response as `GET /cart`).
+
+```http
+curl --request POST "https://example-store.com/wp-json/wc/store/cart/update-item?key=1ff1de774005f8da13f42943881c655f&quantity=3"
+```
+
+### Delete single cart item
+
+Delete/remove an item from the cart.
+
+```http
+POST /cart/remove-item/
+```
+
+| Attribute | Type   | Required | Description                       |
+| :-------- | :----- | :------: | :-------------------------------- |
+| `key`     | string |   Yes    | The key of the cart item to edit. |
+
+Returns the full cart object (same response as `GET /cart`).
+
+```http
+curl --request POST "https://example-store.com/wp-json/wc/store/cart/remove-item?key=1ff1de774005f8da13f42943881c655f"
+```
+
 ## Cart items API
 
 ### List cart items

plugins/woocommerce-blocks/tests/php/RestApi/StoreApi/Controllers/Cart.php

@@ -85,6 +85,72 @@ class Cart extends TestCase {
 		$this->assertEquals( '2900', $data['totals']->total_price );
 	}
 
+	/**
+	 * Test removing a nonexistent cart item.
+	 */
+	public function test_remove_bad_cart_item() {
+		// Test removing a bad cart item - should return 404.
+		$request  = new WP_REST_Request( 'POST', '/wc/store/cart/remove-item' );
+		$request->set_body_params(
+			array(
+				'key' => 'bad_item_key_123',
+			)
+		);
+		$response = $this->server->dispatch( $request );
+		$data     = $response->get_data();
+
+		$this->assertEquals( 404, $response->get_status() );
+		$this->assertEquals( 'woocommerce_rest_cart_invalid_key', $data['code'] );
+	}
+
+	/**
+	 * Test remove cart item.
+	 */
+	public function test_remove_cart_item() {
+		// Test removing a valid cart item - should return updated cart.
+		$request  = new WP_REST_Request( 'POST', '/wc/store/cart/remove-item' );
+		$request->set_body_params(
+			array(
+				'key' => $this->keys[0],
+			)
+		);
+		$response = $this->server->dispatch( $request );
+		$data     = $response->get_data();
+
+		$this->assertEquals( 200, $response->get_status() );
+		$this->assertEquals( 1, $data['items_count'] );
+		$this->assertEquals( 1, count( $data['items'] ) );
+		$this->assertEquals( '10', $data['items_weight'] );
+		$this->assertEquals( '1000', $data['totals']->total_items );
+
+		// Test removing same item again - should return 404 (item is already removed).
+		$response = $this->server->dispatch( $request );
+		$data     = $response->get_data();
+
+		$this->assertEquals( 404, $response->get_status() );
+		$this->assertEquals( 'woocommerce_rest_cart_invalid_key', $data['code'] );
+	}
+
+	/**
+	 * Test changing the quantity of a cart item.
+	 */
+	public function test_update_item() {
+		$request = new WP_REST_Request( 'POST', '/wc/store/cart/update-item' );
+		$request->set_body_params(
+			array(
+				'key'      => $this->keys[0],
+				'quantity' => 10,
+			)
+		);
+		$response = $this->server->dispatch( $request );
+		$data     = $response->get_data();
+
+		$this->assertEquals( 200, $response->get_status() );
+		$this->assertEquals( 10, $data['items'][0]['quantity'] );
+		$this->assertEquals( 11, $data['items_count'] );
+		$this->assertEquals( '11000', $data['totals']->total_items );
+	}
+
 	/**
 	 * Test applying coupon to cart.
 	 */