fix(ListWrapper): follow JS semantics

modules/angular2/src/facade/collection.dart

@@ -135,16 +135,7 @@ class ListWrapper {
   static String join(List l, String s) => l.join(s);
   static bool isEmpty(Iterable list) => list.isEmpty;
   static void fill(List l, value, [int start = 0, int end]) {
-    // JS semantics
+    l.fillRange(_startOffset(l, start), _endOffset(l, end), value);
-    // see https://github.com/google/traceur-compiler/blob/81880cd3f17bac7de90a4cd0339e9f1a9f61d24c/src/runtime/polyfills/Array.js#L94
-    int len = l.length;
-    start = start < 0 ? max(len + start, 0) : min(start, len);
-    if (end == null) {
-      end = len;
-    } else {
-      end = end < 0 ? max(len + end, 0) : min(end, len);
-    }
-    l.fillRange(start, end, value);
   }
   static bool equals(List a, List b) {
     if (a.length != b.length) return false;
@@ -153,10 +144,11 @@ class ListWrapper {
     }
     return true;
   }
-  static List slice(List l, int from, int to) {
+  static List slice(List l, [int from = 0, int to]) {
-    return l.sublist(from, to);
+    return l.sublist(_startOffset(l, from), _endOffset(l, to));
   }
   static List splice(List l, int from, int length) {
+    from = _startOffset(l, from);
     var to = from + length;
     var sub = l.sublist(from, to);
     l.removeRange(from, to);
@@ -165,6 +157,21 @@ class ListWrapper {
   static void sort(List l, compareFn(a,b)) {
     l.sort(compareFn);
   }
+
+  // JS splice, slice, fill functions can take start < 0 which indicates a position relative to
+  // the end of the list
+  static int _startOffset(List l, int start) {
+    int len = l.length;
+    return start = start < 0 ? max(len + start, 0) : min(start, len);
+  }
+
+  // JS splice, slice, fill functions can take end < 0 which indicates a position relative to
+  // the end of the list
+  static int _endOffset(List l, int end) {
+    int len = l.length;
+    if (end == null) return len;
+    return end < 0 ? max(len + end, 0) : min(end, len);
+  }
 }
 
 bool isListLikeIterable(obj) => obj is Iterable;

modules/angular2/src/facade/collection.es6

@@ -184,7 +184,7 @@ export class ListWrapper {
     return list.length == 0;
   }
   static fill(list:List, value, start:int = 0, end:int = null) {
-    list.fill(value, start, end === null ? undefined: end);
+    list.fill(value, start, end === null ? undefined : end);
   }
   static equals(a:List, b:List):boolean {
     if(a.length != b.length) return false;
@@ -193,8 +193,8 @@ export class ListWrapper {
     }
     return true;
   }
-  static slice(l:List, from:int, to:int):List {
+  static slice(l:List, from:int = 0, to:int = null):List {
-    return l.slice(from, to);
+    return l.slice(from, to === null ? undefined : to);
   }
   static splice(l:List, from:int, length:int):List {
     return l.splice(from, length);

modules/angular2/src/facade/collection.ts

@@ -170,7 +170,9 @@ export class ListWrapper {
     }
     return true;
   }
-  static slice<T>(l: List<T>, from: int, to: int): List<T> { return l.slice(from, to); }
+  static slice<T>(l: List<T>, from: int = 0, to: int = null): List<T> {
+    return l.slice(from, to === null ? undefined : to);
+  }
   static splice<T>(l: List<T>, from: int, length: int): List<T> { return l.splice(from, length); }
   static sort<T>(l: List<T>, compareFn: (a: T, b: T) => number) { l.sort(compareFn); }
 }

modules/angular2/test/facade/collection_spec.js

@@ -5,12 +5,68 @@ import {List, ListWrapper} from 'angular2/src/facade/collection';
 
 export function main() {
   describe('ListWrapper', () => {
+    var l: List;
+
     describe('splice', () => {
-      it('should remove sublist of given length and return it',  () => {
+      it('should remove sublist of given length and return it', () => {
         var list = [1, 2, 3, 4, 5, 6];
         expect(ListWrapper.splice(list, 1, 3)).toEqual([2, 3, 4]);
         expect(list).toEqual([1, 5, 6]);
       });
+
+      it('should support negative start', () => {
+        var list = [1, 2, 3, 4, 5, 6];
+        expect(ListWrapper.splice(list, -5, 3)).toEqual([2, 3, 4]);
+        expect(list).toEqual([1, 5, 6]);
+      });
+    });
+
+    describe('fill', () => {
+      beforeEach(() => {
+        l = [1, 2, 3, 4];
+      });
+
+      it('should fill the whole list if neither start nor end are specified', () => {
+        ListWrapper.fill(l, 9);
+        expect(l).toEqual([9, 9, 9, 9]);
+      });
+
+      it('should fill up to the end if end is not specified', () => {
+        ListWrapper.fill(l, 9, 1);
+        expect(l).toEqual([1, 9, 9, 9]);
+      });
+
+      it('should support negative start', () => {
+        ListWrapper.fill(l, 9, -1);
+        expect(l).toEqual([1, 2, 3, 9]);
+      });
+
+      it('should support negative end', () => {
+        ListWrapper.fill(l, 9, -2, -1);
+        expect(l).toEqual([1, 2, 9, 4]);
+      });
+    });
+
+    describe('slice', () => {
+      beforeEach(() => {
+        l = [1, 2, 3, 4];
+      });
+
+      it('should return the whole list if neither start nor end are specified', () => {
+        expect(ListWrapper.slice(l)).toEqual([1, 2, 3, 4]);
+      });
+
+      it('should return up to the end if end is not specified', () => {
+        expect(ListWrapper.slice(l, 1)).toEqual([2, 3, 4]);
+      });
+
+      it('should support negative start', () => {
+        expect(ListWrapper.slice(l, -1)).toEqual([4]);
+      });
+
+      it('should support negative end', () => {
+        expect(ListWrapper.slice(l, -3, -1)).toEqual([2, 3]);
+      });
     });
  });
 }