perf(ngRepeat): move work to compile fn

this has impact only on nested repeaters where the number of columns is significant

src/ng/directive/ngRepeat.js

@@ -233,50 +233,56 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
     priority: 1000,
     terminal: true,
     $$tlb: true,
-    link: function($scope, $element, $attr, ctrl, $transclude){
-        var expression = $attr.ngRepeat;
-        var match = expression.match(/^\s*([\s\S]+?)\s+in\s+([\s\S]+?)(?:\s+as\s+([\s\S]+?))?(?:\s+track\s+by\s+([\s\S]+?))?\s*$/),
-          trackByExp, trackByExpGetter, aliasAs, trackByIdExpFn, trackByIdArrayFn, trackByIdObjFn,
-          lhs, rhs, valueIdentifier, keyIdentifier,
-          hashFnLocals = {$id: hashKey};
+    compile: function ngRepeatCompile($element, $attr) {
+      var expression = $attr.ngRepeat;
+      var ngRepeatEndComment = document.createComment(' end ngRepeat: ' + expression + ' ');
 
-        var ngRepeatEndComment = document.createComment(' end ngRepeat: ' + expression + ' ');
+      var match = expression.match(/^\s*([\s\S]+?)\s+in\s+([\s\S]+?)(?:\s+as\s+([\s\S]+?))?(?:\s+track\s+by\s+([\s\S]+?))?\s*$/);
 
-        if (!match) {
-          throw ngRepeatMinErr('iexp', "Expected expression in form of '_item_ in _collection_[ track by _id_]' but got '{0}'.",
+      if (!match) {
+        throw ngRepeatMinErr('iexp', "Expected expression in form of '_item_ in _collection_[ track by _id_]' but got '{0}'.",
             expression);
-        }
+      }
 
-        lhs = match[1];
-        rhs = match[2];
-        aliasAs = match[3];
-        trackByExp = match[4];
+      var lhs = match[1];
+      var rhs = match[2];
+      var aliasAs = match[3];
+      var trackByExp = match[4];
 
-        if (trackByExp) {
-          trackByExpGetter = $parse(trackByExp);
+      match = lhs.match(/^(?:([\$\w]+)|\(([\$\w]+)\s*,\s*([\$\w]+)\))$/);
+
+      if (!match) {
+        throw ngRepeatMinErr('iidexp', "'_item_' in '_item_ in _collection_' should be an identifier or '(_key_, _value_)' expression, but got '{0}'.",
+            lhs);
+      }
+      var valueIdentifier = match[3] || match[1];
+      var keyIdentifier = match[2];
+
+      var trackByExpGetter, trackByIdExpFn, trackByIdArrayFn, trackByIdObjFn;
+      var hashFnLocals = {$id: hashKey};
+
+      if (trackByExp) {
+        trackByExpGetter = $parse(trackByExp);
+      } else {
+        trackByIdArrayFn = function (key, value) {
+          return hashKey(value);
+        };
+        trackByIdObjFn = function (key) {
+          return key;
+        };
+      }
+
+      return function ngRepeatLink($scope, $element, $attr, ctrl, $transclude) {
+
+        if (trackByExpGetter) {
           trackByIdExpFn = function(key, value, index) {
             // assign key, value, and $index to the locals so that they can be used in hash functions
             if (keyIdentifier) hashFnLocals[keyIdentifier] = key;
             hashFnLocals[valueIdentifier] = value;
             hashFnLocals.$index = index;
             return trackByExpGetter($scope, hashFnLocals);
           };
-        } else {
-          trackByIdArrayFn = function(key, value) {
-            return hashKey(value);
-          };
-          trackByIdObjFn = function(key) {
-            return key;
-          };
-        }
-
-        match = lhs.match(/^(?:([\$\w]+)|\(([\$\w]+)\s*,\s*([\$\w]+)\))$/);
-        if (!match) {
-          throw ngRepeatMinErr('iidexp', "'_item_' in '_item_ in _collection_' should be an identifier or '(_key_, _value_)' expression, but got '{0}'.",
-                                                                    lhs);
         }
-        valueIdentifier = match[3] || match[1];
-        keyIdentifier = match[2];
 
         // Store a list of elements from previous run. This is a hash where key is the item from the
         // iterator, and the value is objects with following properties.
@@ -402,6 +408,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
           }
           lastBlockMap = nextBlockMap;
         });
+      };
     }
   };