Merge pull request #15829 from woocommerce/fix/15725

Use type check in coupon constructor

includes/class-wc-cart.php

@@ -1736,6 +1736,13 @@ class WC_Cart {
 		// Get the coupon.
 		$the_coupon = new WC_Coupon( $coupon_code );
 
+		// Prevent adding coupons by post ID.
+		if ( $the_coupon->get_code() !== $coupon_code ) {
+			$the_coupon->set_code( $coupon_code );
+			$the_coupon->add_coupon_message( WC_Coupon::E_WC_COUPON_NOT_EXIST );
+			return false;
+		}
+
 		// Check it can be used with cart.
 		if ( ! $the_coupon->is_valid() ) {
 			wc_add_notice( $the_coupon->get_error_message(), 'error' );

includes/class-wc-coupon.php

@@ -85,11 +85,18 @@ class WC_Coupon extends WC_Legacy_Coupon {
 		} elseif ( $coupon = apply_filters( 'woocommerce_get_shop_coupon_data', false, $data ) ) {
 			$this->read_manual_coupon( $data, $coupon );
 			return;
-		} elseif ( is_numeric( $data ) && 'shop_coupon' === get_post_type( $data ) ) {
+		} elseif ( is_int( $data ) && 'shop_coupon' === get_post_type( $data ) ) {
 			$this->set_id( $data );
 		} elseif ( ! empty( $data ) ) {
-			$this->set_id( wc_get_coupon_id_by_code( $data ) );
+			$id = wc_get_coupon_id_by_code( $data );
+
+			// Need to support numeric strings for backwards compatibility.
+			if ( ! $id && 'shop_coupon' === get_post_type( $data ) ) {
+				$this->set_id( $data );
+			} else {
+				$this->set_id( $id );
 				$this->set_code( $data );
+			}
 		} else {
 			$this->set_object_read( true );
 		}

tests/unit-tests/cart/cart.php

@@ -587,6 +587,25 @@ class WC_Tests_Cart extends WC_Unit_Test_Case {
 
 	}
 
+	/**
+	 * Test add_discount allows coupons by code but not by ID.
+	 *
+	 * @since 3.2
+	 */
+	public function test_add_discount_code_id() {
+
+		$coupon = new WC_Coupon;
+		$coupon->set_code( 'test' );
+		$coupon->set_amount( 100 );
+		$coupon->save();
+
+		$success = WC()->cart->add_discount( $coupon->get_code() );
+		$this->assertTrue( $success );
+
+		$success = WC()->cart->add_discount( (string) $coupon->get_id() );
+		$this->assertFalse( $success );
+	}
+
 	public function test_add_invidual_use_coupon() {
 		$iu_coupon = WC_Helper_Coupon::create_coupon( 'code1' );
 		$iu_coupon->set_individual_use( true );

tests/unit-tests/coupon/coupon.php

@@ -6,6 +6,46 @@
  */
 class WC_Tests_Coupon extends WC_Unit_Test_Case {
 
+	/**
+	 * Test the code/id differentiation of the coupon constructor.
+	 *
+	 * @since 3.2
+	 */
+	public function test_constructor_code_id() {
+		$string_code_1 = 'test';
+
+		// Coupon with a standard string code.
+		$coupon_1 = new WC_Coupon;
+		$coupon_1->set_code( $string_code_1 );
+		$coupon_1->save();
+
+		// Coupon with a string code that is the same as coupon 1's ID.
+		$coupon_2 = new WC_Coupon;
+		$coupon_2->set_code( (string) $coupon_1->get_id() );
+		$coupon_2->save();
+
+		$int_id_1 = $coupon_1->get_id();
+		$int_id_2 = $coupon_2->get_id();
+		$string_code_2 = $coupon_2->get_code();
+
+		// Test getting a coupon by integer ID.
+		$test_coupon = new WC_Coupon( $int_id_1 );
+		$this->assertEquals( $int_id_1, $test_coupon->get_id() );
+		$test_coupon = new WC_Coupon( $int_id_2 );
+		$this->assertEquals( $int_id_2, $test_coupon->get_id() );
+
+		// Test getting a coupon by string code.
+		$test_coupon = new WC_Coupon( $string_code_1 );
+		$this->assertEquals( $string_code_1, $test_coupon->get_code() );
+		$test_coupon = new WC_Coupon( $string_code_2 );
+		$this->assertEquals( $string_code_2, $test_coupon->get_code() );
+
+		// Test getting a coupon by string id.
+		// Required for backwards compatibility, but will try and initialize coupon by code if possible first.
+		$test_coupon = new WC_Coupon( (string) $coupon_2->get_id() );
+		$this->assertEquals( $coupon_2->get_id(), $test_coupon->get_id() );
+	}
+
 	/**
 	 * Test add_discount method.
 	 *