Fix bugs when switching between EditSessions

spec/app/editor-spec.coffee

@@ -92,20 +92,24 @@ describe "Editor", ->
       expect(otherBuffer.subscriptionCount()).toBe 1
 
   describe ".setBuffer(buffer)", ->
+    otherBuffer = null
+
+    beforeEach ->
+      otherBuffer = new Buffer
+
     it "sets the cursor to the beginning of the file", ->
       expect(editor.getCursorScreenPosition()).toEqual(row: 0, column: 0)
 
     it "recalls the cursor position and scroll position when the same buffer is re-assigned", ->
       editor.attachToDom()
+
       editor.height(editor.lineHeight * 5)
       editor.width(editor.charWidth * 30)
       editor.setCursorScreenPosition([8, 28])
-      advanceClock()
-
       previousScrollTop = editor.verticalScrollbar.scrollTop()
       previousScrollLeft = editor.scrollView.scrollLeft()
 
-      editor.setBuffer(new Buffer)
+      editor.setBuffer(otherBuffer)
       expect(editor.getCursorScreenPosition()).toEqual [0, 0]
       expect(editor.verticalScrollbar.scrollTop()).toBe 0
       expect(editor.scrollView.scrollLeft()).toBe 0
@@ -118,7 +122,6 @@ describe "Editor", ->
     it "recalls the undo history of the buffer when it is re-assigned", ->
       editor.insertText('xyz')
 
-      otherBuffer = new Buffer
       editor.setBuffer(otherBuffer)
       editor.insertText('abc')
       expect(otherBuffer.lineForRow(0)).toBe 'abc'
@@ -135,15 +138,15 @@ describe "Editor", ->
       editor.redo()
       expect(otherBuffer.lineForRow(0)).toBe 'abc'
 
-    it "fully unsubscribes from the previously assigned buffer", ->
-      otherBuffer = new Buffer
-      previousSubscriptionCount = otherBuffer.subscriptionCount()
-
+    it "unsubscribes from the previously assigned buffer", ->
       editor.setBuffer(otherBuffer)
-      expect(otherBuffer.subscriptionCount()).toBeGreaterThan previousSubscriptionCount
+
+      previousSubscriptionCount = buffer.subscriptionCount()
 
       editor.setBuffer(buffer)
-      expect(otherBuffer.subscriptionCount()).toBe previousSubscriptionCount
+      editor.setBuffer(otherBuffer)
+
+      expect(buffer.subscriptionCount()).toBe previousSubscriptionCount
 
     it "resizes the vertical scrollbar based on the new buffer's height", ->
       editor.attachToDom(heightInLines: 5)
@@ -153,6 +156,17 @@ describe "Editor", ->
       editor.setBuffer(new Buffer(require.resolve('fixtures/sample.txt')))
       expect(editor.verticalScrollbar.prop('scrollHeight')).toBeLessThan originalHeight
 
+    it "handles buffer manipulation correctly after switching to a new buffer", ->
+      editor.attachToDom()
+      editor.insertText("abc\n")
+      expect(editor.lineElementForScreenRow(0).text()).toBe 'abc'
+
+      editor.setBuffer(otherBuffer)
+      expect(editor.lineElementForScreenRow(0).html()).toBe ' '
+
+      editor.insertText("def\n")
+      expect(editor.lineElementForScreenRow(0).text()).toBe 'def'
+
   describe ".clipScreenPosition(point)", ->
     it "selects the nearest valid position to the given point", ->
       expect(editor.clipScreenPosition(row: 1000, column: 0)).toEqual(row: buffer.getLastRow(), column: buffer.lineForRow(buffer.getLastRow()).length)

src/app/edit-session.coffee

@@ -20,6 +20,9 @@ class EditSession
   constructor: (@editor, @buffer) ->
     @setCursorScreenPosition([0, 0])
 
+  destroy: ->
+    @renderer.destroy()
+
   serialize: ->
     buffer: @buffer.serialize()
     scrollTop: @getScrollTop()

src/app/editor.coffee

@@ -317,36 +317,31 @@ class Editor extends View
     @renderer.destroyFoldsContainingBufferRow(bufferRow)
 
   setBuffer: (buffer) ->
-    if @buffer
-      @saveCurrentEditSession()
-      @unsubscribeFromBuffer()
-
-    @buffer = buffer
-    @trigger 'editor-path-change'
-    @buffer.on "path-change.editor#{@id}", => @trigger 'editor-path-change'
-
-    @loadEditSessionForBuffer(@buffer)
-
-    @buffer.on "change.editor#{@id}", (e) => @handleBufferChange(e)
-    @renderer.on 'change', (e) => @handleRendererChange(e)
+    @loadEditSessionForBuffer(buffer)
 
   setRenderer: (renderer) ->
     @renderer?.off()
     @renderer = renderer
+    @renderer.on 'change', (e) => @handleRendererChange(e)
 
-  editSessionForBuffer: (buffer) ->
+    @unsubscribeFromBuffer() if @buffer
+    @buffer = renderer.buffer
+    @buffer.on "path-change.editor#{@id}", => @trigger 'editor-path-change'
+    @buffer.on "change.editor#{@id}", (e) => @handleBufferChange(e)
+    @trigger 'editor-path-change'
+
+  editSessionIndexForBuffer: (buffer) ->
     for editSession, index in @editSessions
-      return [editSession, index] if editSession.buffer == buffer
-    [undefined, -1]
+      return index if editSession.buffer == buffer
+    null
 
   loadEditSessionForBuffer: (buffer) ->
-    [editSession, index] = @editSessionForBuffer(buffer)
-    if editSession
-      @activeEditSessionIndex = index
-    else
+    index = @editSessionIndexForBuffer(buffer)
+    unless index?
+      index = @editSessions.length
       @editSessions.push(new EditSession(this, buffer))
-      @activeEditSessionIndex = @editSessions.length - 1
-    @loadEditSession()
+
+    @loadEditSession(index)
 
   loadNextEditSession: ->
     nextIndex = (@activeEditSessionIndex + 1) % @editSessions.length
@@ -360,7 +355,8 @@ class Editor extends View
   loadEditSession: (index=@activeEditSessionIndex) ->
     editSession = @editSessions[index]
     throw new Error("Edit session not found") unless editSession
-    @setBuffer(editSession.buffer) unless @buffer == editSession.buffer
+    @saveCurrentEditSession() if @activeEditSessionIndex?
+
     @activeEditSessionIndex = index
     @setRenderer(editSession.getRenderer())
     if @attached
@@ -752,7 +748,10 @@ class Editor extends View
     return super if keepData
 
     @trigger 'before-remove'
+
+    @destroyEditSessions()
     @unsubscribeFromBuffer()
+
     $(window).off ".editor#{@id}"
     rootView = @rootView()
     rootView?.off ".editor#{@id}"
@@ -761,7 +760,9 @@ class Editor extends View
 
   unsubscribeFromBuffer: ->
     @buffer.off ".editor#{@id}"
-    @renderer.destroy()
+
+  destroyEditSessions: ->
+    session.destroy() for session in @editSessions
 
   stateForScreenRow: (row) ->
     @renderer.lineForRow(row).state