Allow empty pattern when any attribute is present

plugins/removeEmptyContainers.js

@@ -24,12 +24,13 @@ var container = require('./_collections').elemsGroups.container;
  *
  * @author Kir Belevich
  */
-exports.fn = function(item) {
+exports.fn = function (item) {
   return (
     item.isElem(container) === false ||
     item.isEmpty() === false ||
     item.isElem('svg') ||
-    (item.isElem('pattern') && item.hasAttrLocal('href')) ||
+    // empty patterns may contain reusable configuration
+    (item.isElem('pattern') && Object.keys(item.attrs).length !== 0) ||
     // The 'g' may not have content, but the filter may cause a rectangle
     // to be created and filled with pattern.
     (item.isElem('g') && item.hasAttr('filter')) ||

test/regression.js

@@ -95,6 +95,8 @@ const runTests = async ({ svgFiles }) => {
     if (
       // hard to detect the end of animation
       name.startsWith('animate-') ||
+      // breaks because of optimisation despite of script
+      name === 'interact-pointer-04-f' ||
       // other cases which require complex changes
       name === 'painting-marker-07-f' ||
       name === 'pservers-grad-18-b' ||
@@ -108,8 +110,6 @@ const runTests = async ({ svgFiles }) => {
       // unstable test
       name === 'filters-light-04-f' ||
       // mismatched draft cases
-      name === 'interact-pointer-04-f' ||
-      name === 'pservers-pattern-05-f' ||
       name === 'struct-cond-overview-03-f' ||
       name === 'struct-use-07-b' ||
       name === 'styling-css-10-f' ||