From 458b3975ea0c0de7c38df6998aa2b3facf6f730d Mon Sep 17 00:00:00 2001
From: Max Mikhailov <seven.phases.max@gmail.com>
Date: Wed, 31 May 2017 23:25:26 +0300
Subject: [PATCH] update mergeRules (no separate !important rules + cleanup)

---
 lib/less/visitors/to-css-visitor.js | 71 ++++++++++-------------------
 test/css/merge.css                  |  9 ++--
 test/less/merge.less                |  9 ++--
 3 files changed, 34 insertions(+), 55 deletions(-)

diff --git a/lib/less/visitors/to-css-visitor.js b/lib/less/visitors/to-css-visitor.js
index 009ac056..74990bc9 100644
--- a/lib/less/visitors/to-css-visitor.js
+++ b/lib/less/visitors/to-css-visitor.js
@@ -321,62 +321,37 @@ ToCSSVisitor.prototype = {
         }
     },
 
-    _mergeRules: function (rules) {
-        if (!rules) { return; }
-
-        var groups = {},
-            parts,
-            rule,
-            key;
+    _mergeRules: function(rules) {
+        if (!rules) {
+            return; 
+        }
 
+        var groups    = {},
+            groupsArr = [];
+        
         for (var i = 0; i < rules.length; i++) {
-            rule = rules[i];
-
-            if ((rule instanceof tree.Declaration) && rule.merge) {
-                key = [rule.name,
-                    rule.important ? "!" : ""].join(",");
-
-                if (!groups[key]) {
-                    groups[key] = [];
-                } else {
-                    rules.splice(i--, 1);
-                }
-
+            var rule = rules[i];
+            if (rule.merge) {
+                var key = rule.name;
+                groups[key] ? rules.splice(i--, 1) : 
+                    groupsArr.push(groups[key] = []);
                 groups[key].push(rule);
             }
         }
 
-        Object.keys(groups).map(function (k) {
-
-            function toExpression(values) {
-                return new (tree.Expression)(values.map(function (p) {
-                    return p.value;
-                }));
-            }
-
-            function toValue(values) {
-                return new (tree.Value)(values.map(function (p) {
-                    return p;
-                }));
-            }
-
-            parts = groups[k];
-
-            if (parts.length > 1) {
-                rule = parts[0];
-                var spacedGroups = [];
-                var lastSpacedGroup = [];
-                parts.map(function (p) {
-                    if (p.merge === "+") {
-                        if (lastSpacedGroup.length > 0) {
-                            spacedGroups.push(toExpression(lastSpacedGroup));
-                        }
-                        lastSpacedGroup = [];
+        groupsArr.forEach(function(group) {
+            if (group.length > 0) {
+                var result = group[0],
+                    space  = [],
+                    comma  = [new tree.Expression(space)];
+                group.forEach(function(rule) {
+                    if ((rule.merge === '+') && (space.length > 0)) {
+                        comma.push(new tree.Expression(space = []));
                     }
-                    lastSpacedGroup.push(p);
+                    space.push(rule.value);
+                    result.important = result.important || rule.important;
                 });
-                spacedGroups.push(toExpression(lastSpacedGroup));
-                rule.value = toValue(spacedGroups);
+                result.value = new tree.Value(comma);
             }
         });
     },
diff --git a/test/css/merge.css b/test/css/merge.css
index fe29dc83..b5d079b5 100644
--- a/test/css/merge.css
+++ b/test/css/merge.css
@@ -10,16 +10,17 @@
   background: url(data://img1.png);
 }
 .test4 {
-  transform: rotate(90deg), skew(30deg);
-  transform: scale(2, 4) !important;
+  transform: rotate(90deg), skew(30deg), scale(2, 4) !important;
 }
 .test5 {
-  transform: rotate(90deg), skew(30deg);
-  transform: scale(2, 4) !important;
+  transform: rotate(90deg), skew(30deg), scale(2, 4) !important;
 }
 .test6 {
   transform: scale(2, 4);
 }
+.test7 {
+  transform: scale(2, 4), scale(2, 4), scale(2, 4) !important;
+}
 .test-interleaved {
   transform: t1, t2, t3;
   background: b1, b2, b3;
diff --git a/test/less/merge.less b/test/less/merge.less
index 9d37f67a..7cac833b 100644
--- a/test/less/merge.less
+++ b/test/less/merge.less
@@ -36,17 +36,20 @@
   .first-background();
 }
 .test4 {
-  // Won't merge values from sources that merked as !important, for backwards compatibility with css
   .first-transform();
   .fifth-transform();
 }
 .test5 {
-  // Won't merge values from mixins that merked as !important, for backwards compatibility with css
   .first-transform();
   .second-transform() !important;
 }
 .test6 {
-  // Ignores !merge if no peers found
+  .second-transform();
+}
+.test7 {
+  // inherit !important from merged subrules
+  .second-transform();
+  .second-transform() !important;
   .second-transform();
 }