Allow webhooks without livemode to be processed.

changelog/fix-3131-notification-webhooks-not-working

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Allow webhooks without livemode to be received.

includes/class-wc-payments-webhook-processing-service.php

@@ -213,6 +213,10 @@ public function process( array $event_body ) {
 	 * @throws Invalid_Webhook_Data_Exception Event mode does not match the gateway mode.
 	 */
 	private function is_webhook_mode_mismatch( array $event_body ): bool {
+		if ( ! $this->has_webhook_property( $event_body, 'livemode' ) ) {
+			return false;
+		}
+
 		$is_gateway_live_mode = WC_Payments::mode()->is_live();
 		$is_event_live_mode   = $this->read_webhook_property( $event_body, 'livemode' );
 
@@ -689,6 +693,18 @@ private function read_webhook_property( $array, $key ) {
 		return $array[ $key ];
 	}
 
+	/**
+	 * Safely check whether a webhook contains a property.
+	 *
+	 * @param array  $array Array to read from.
+	 * @param string $key   ID to fetch on.
+	 *
+	 * @return bool
+	 */
+	private function has_webhook_property( $array, $key ) {
+		return isset( $array[ $key ] );
+	}
+
 	/**
 	 * Gets the order related to the event intent id.
 	 *

includes/core/server/request/class-paginated.php

@@ -95,7 +95,6 @@ public function set_page( int $page ) {
 		$this->set_param( 'page', $page );
 	}
 
-
 	/**
 	 * Set page size.
 	 *

tests/unit/test-class-wc-payments-webhook-processing-service.php

@@ -12,6 +12,7 @@
 use WCPay\Exceptions\Invalid_Payment_Method_Exception;
 use WCPay\Exceptions\Invalid_Webhook_Data_Exception;
 use WCPay\Exceptions\Rest_Request_Exception;
+use WCPay\Logger;
 
 // Need to use WC_Mock_Data_Store.
 require_once dirname( __FILE__ ) . '/helpers/class-wc-mock-wc-data-store.php';
@@ -1339,4 +1340,32 @@ public function test_dispute_funds_reinstated_order_note() {
 		// Run the test.
 		$this->webhook_processing_service->process( $this->event_body );
 	}
+
+	/**
+	 * @dataProvider provider_mode_mismatch_detection
+	 */
+	public function test_mode_mismatch_detection( $livemode, $expectation ) {
+		$note = [ 'abc1234' ];
+
+		$this->event_body['type'] = 'wcpay.notification';
+		$this->event_body['id']   = 'evt_XYZ';
+		$this->event_body['data'] = $note;
+		if ( ! is_null( $livemode ) ) {
+			$this->event_body['livemode'] = $livemode;
+		}
+
+		$this->mock_remote_note_service->expects( $expectation )
+			->method( 'put_note' )
+			->with( $note );
+
+		$this->webhook_processing_service->process( $this->event_body );
+	}
+
+	public function provider_mode_mismatch_detection() {
+		return [
+			'Live mode webhook is processed.' => [ true, $this->once() ],
+			'Test mode is not processed.'     => [ false, $this->never() ],
+			'No mode proceeds'                => [ null, $this->once() ],
+		];
+	}
 }