Buffer.setText emits the proper change events

spec/atom/buffer-spec.coffee

@@ -102,6 +102,24 @@ describe 'Buffer', ->
           expect(buffer.getLine(3)).toBe "    var pivot = sort(Array.apply(this, arguments));"
           expect(buffer.getLine(4)).toBe "};"
 
+  describe ".setText(text)", ->
+    it "changes the entire contents of the buffer and emits a change event", ->
+      lastRow = buffer.lastRow()
+      expectedPreRange = new Range([0,0], [lastRow, buffer.getLine(lastRow).length])
+      changeHandler = jasmine.createSpy('changeHandler')
+      buffer.on 'change', changeHandler
+
+      newText = "I know you are.\nBut what am I?"
+      buffer.setText(newText)
+
+      expect(buffer.getText()).toBe newText
+      expect(changeHandler).toHaveBeenCalled()
+
+      [event] = changeHandler.argsForCall[0]
+      expect(event.string).toBe newText
+      expect(event.preRange).toEqual expectedPreRange
+      expect(event.postRange).toEqual(new Range([0, 0], [1, 14]))
+
   describe ".save()", ->
     describe "when the buffer has a path", ->
       filePath = null

src/atom/buffer.coffee

@@ -8,6 +8,7 @@ class Buffer
 
   constructor: (@path) ->
     @url = @path # we want this to be path on master, but let's not break it on a branch
+    @lines = ['']
     if @path and fs.exists(@path)
       @setText(fs.read(@path))
     else
@@ -17,7 +18,10 @@ class Buffer
     @lines.join('\n')
 
   setText: (text) ->
-    @lines = text.split('\n')
+    @change(@getRange(), text)
+
+  getRange: ->
+    new Range([0, 0], [@lastRow(), @lastLine().length])
 
   getTextInRange: (range) ->
     if range.start.row == range.end.row
@@ -37,6 +41,15 @@ class Buffer
   getLine: (row) ->
     @lines[row]
 
+  numLines: ->
+    @getLines().length
+
+  lastRow: ->
+    @getLines().length - 1
+
+  lastLine: ->
+    @getLine(@lastRow())
+
   change: (preRange, newText) ->
     postRange = new Range(_.clone(preRange.start), _.clone(preRange.start))
     prefix = @lines[preRange.start.row][0...preRange.start.column]
@@ -66,8 +79,7 @@ class Buffer
 
     @trigger 'change', { preRange, postRange, string: newText }
 
-  numLines: ->
-    @getLines().length
+
 
   save: ->
     if not @path then throw new Error("Tried to save buffer with no url")