Only load serialized content if the disk content's have not changed.

spec/text-buffer-spec.coffee

@@ -949,24 +949,48 @@ describe 'TextBuffer', ->
           expect(buffer2.getText()).toBe(buffer.getText())
 
     describe "when the serialized buffer had unsaved changes", ->
-      it "restores the previous unsaved state of the buffer", ->
-        previousText = buffer.getText()
-        buffer.setText("abc")
+      describe "when the disk contents were changed since serialization", ->
+        it "loads the disk contents instead of the previous unsaved state", ->
+          buffer.release()
 
-        state = buffer.serialize()
-        expect(state.getObject('text')).toBe 'abc'
+          filePath = temp.openSync('atom').path
+          fs.writeSync(filePath, "words")
+          buffer = project.openSync(filePath).buffer
+          buffer.setText("BUFFER CHANGE")
 
-        buffer2 = deserialize(state, {project})
+          state = buffer.serialize()
+          expect(state.getObject('text')).toBe 'BUFFER CHANGE'
+          fs.writeSync(filePath, "DISK CHANGE")
 
-        waitsFor ->
-          buffer2.cachedDiskContents
+          buffer2 = deserialize(state, {project})
 
-        runs ->
-          expect(buffer2.getPath()).toBe(buffer.getPath())
-          expect(buffer2.getText()).toBe(buffer.getText())
-          expect(buffer2.isModified()).toBeTruthy()
-          buffer2.setText(previousText)
-          expect(buffer2.isModified()).toBeFalsy()
+          waitsFor ->
+            buffer2.cachedDiskContents
+
+          runs ->
+            expect(buffer2.getPath()).toBe(buffer.getPath())
+            expect(buffer2.getText()).toBe("DISK CHANGE")
+            expect(buffer2.isModified()).toBeFalsy()
+
+      describe "when the disk contents are the same since serialization", ->
+        it "restores the previous unsaved state of the buffer", ->
+          previousText = buffer.getText()
+          buffer.setText("abc")
+
+          state = buffer.serialize()
+          expect(state.getObject('text')).toBe 'abc'
+
+          buffer2 = deserialize(state, {project})
+
+          waitsFor ->
+            buffer2.cachedDiskContents
+
+          runs ->
+            expect(buffer2.getPath()).toBe(buffer.getPath())
+            expect(buffer2.getText()).toBe(buffer.getText())
+            expect(buffer2.isModified()).toBeTruthy()
+            buffer2.setText(previousText)
+            expect(buffer2.isModified()).toBeFalsy()
 
     describe "when the serialized buffer was unsaved and had no path", ->
       it "restores the previous unsaved state of the buffer", ->

src/file.coffee

@@ -1,3 +1,4 @@
+crypto = require 'crypto'
 path = require 'path'
 pathWatcher = require 'pathwatcher'
 Q = require 'q'
@@ -68,6 +69,9 @@ class File
     else
       @cachedContents
 
+    @setDigest(@cachedContents)
+    @cachedContents
+
   # Public: Reads the contents of the file.
   #
   # * flushCache:
@@ -101,12 +105,19 @@ class File
       promise = Q(@cachedContents)
 
     promise.then (contents) =>
+      @setDigest(contents)
       @cachedContents = contents
 
   # Public: Returns whether the file exists.
   exists: ->
     fsUtils.exists(@getPath())
 
+  setDigest: (contents)->
+    @digest = crypto.createHash('sha1').update(contents ? '').digest('hex')
+
+  getDigest: ->
+    @digest ? @setDigest(@readSync())
+
   # Private:
   handleNativeChangeEvent: (eventType, path) ->
     if eventType is "delete"

src/text-buffer.coffee

@@ -1,4 +1,5 @@
 {Emitter, Subscriber} = require 'emissary'
+crypto = require 'crypto'
 guid = require 'guid'
 Q = require 'q'
 {P} = require 'scandal'
@@ -57,7 +58,6 @@ class TextBuffer
         deserializer: @constructor.name
         version: @constructor.version
         text: @text
-      @loadFromDisk = true
 
     @loaded = false
     @subscribe @text, 'changed', @handleTextChange
@@ -68,12 +68,12 @@ class TextBuffer
 
   loadSync: ->
     @updateCachedDiskContentsSync()
-    @reload() if @loadFromDisk
+    @reload() if @loadFromDisk or @state.get('diskContentsDigest') != @file?.getDigest()
     @text.clearUndoStack()
 
   load: ->
     @updateCachedDiskContents().then =>
-      @reload() if @loadFromDisk
+      @reload() if @loadFromDisk or @state.get('diskContentsDigest') != @file?.getDigest()
       @text.clearUndoStack()
       this
 
@@ -108,6 +108,7 @@ class TextBuffer
   serialize: ->
     state = @state.clone()
     state.set('isModified', @isModified())
+    state.set('diskContentsDigest', @file.getDigest()) if @file
     for marker in state.get('text').getMarkers() when marker.isRemote()
       marker.destroy()
     state