Buffers retain path when file is deleted and can be re-saved

Path watching resumes once the file is saved again. This commit allows files to be created for as-yet nonexistent paths. We won't call `$native.watchPath` until we have at least 1 subscription to the file in JS and the file exists on disk.

Also, we moved execution of the path watcher callbacks until after the callbacks data structure is updated in order to avoid confusing behavior in specs.

native/path_watcher.mm

@@ -109,7 +109,7 @@ static NSMutableArray *gPathWatchers;
       NSLog(@"WARNING: Failed to create kevent for path '%@'", path);
       return nil;
     }
-    
+
     NSMutableDictionary *callbacks = [_callbacksByPath objectForKey:path];
     if (!callbacks) {
       callbacks = [NSMutableDictionary dictionary];
@@ -152,13 +152,13 @@ static NSMutableArray *gPathWatchers;
       NSLog(@"we already have a kevent");
       return YES;
     }
-    
+
     int fd = open([path fileSystemRepresentation], O_EVTONLY, 0);
     if (fd < 0) {
       NSLog(@"WARNING: Could create file descriptor for path '%@'", path);
       return NO;
     }
-    
+
     [_fileDescriptorsByPath setObject:[NSNumber numberWithInt:fd] forKey:path];
 
     struct timespec timeout = { 0, 0 };
@@ -218,7 +218,7 @@ static NSMutableArray *gPathWatchers;
       NSString *eventFlag = nil;
       NSString *newPath = nil;
       NSString *path = [(NSString *)event.udata retain];
-      
+
       if (event.fflags & NOTE_WRITE) {
         eventFlag = @"contents-change";
       }
@@ -242,13 +242,20 @@ static NSMutableArray *gPathWatchers;
           continue;
         }
       }
-      
 
       NSDictionary *callbacks;
       @synchronized(self) {
         callbacks = [NSDictionary dictionaryWithDictionary:[_callbacksByPath objectForKey:path]];
       }
 
+      if ([eventFlag isEqual:@"move"]) {
+        [self changePath:path toNewPath:newPath];
+      }
+
+      if ([eventFlag isEqual:@"remove"]) {
+        [self unwatchPath:path callbackId:nil error:nil];
+      }
+
       dispatch_sync(dispatch_get_main_queue(), ^{
         for (NSString *key in callbacks) {
           WatchCallback callback = [callbacks objectForKey:key];
@@ -256,14 +263,6 @@ static NSMutableArray *gPathWatchers;
         }
       });
 
-      if ([eventFlag isEqual:@"move"]) {
-        [self changePath:path toNewPath:newPath];
-      }
-
-      if ([eventFlag isEqual:@"remove"]) {
-        [self unwatchPath:path callbackId:nil error:nil];
-      }
-      
       [path release];
     }
   }

spec/app/buffer-spec.coffee

@@ -72,7 +72,7 @@ describe 'Buffer', ->
       runs ->
         expect(eventHandler).toHaveBeenCalledWith(bufferToChange)
 
-  describe "when the buffer's on-disk contents change (via another process writing to its file)", ->
+  describe "when the buffer's on-disk contents change", ->
     path = null
     beforeEach ->
       path = "/tmp/tmp.txt"
@@ -85,7 +85,7 @@ describe 'Buffer', ->
       buffer = null
       fs.remove(path) if fs.exists(path)
 
-    it "does not trigger a contents-change event when Atom modifies the file", ->
+    it "does not trigger a change event when Atom modifies the file", ->
       buffer.insert([0,0], "HELLO!")
       changeHandler = jasmine.createSpy("buffer changed")
       buffer.on "change", changeHandler
@@ -129,20 +129,33 @@ describe 'Buffer', ->
           expect(buffer.isModified()).toBeTruthy()
 
   describe "when the buffer's file is deleted (via another process)", ->
-    it "retains its path and reports the buffer as modified", ->
-      path = "/tmp/atom-file-to-delete.txt"
-      fs.write(path, '')
-      bufferToDelete = new Buffer(path)
-      expect(bufferToDelete.getPath()).toBe path
+    [path, bufferToDelete] = []
 
+    beforeEach ->
+      path = "/tmp/atom-file-to-delete.txt"
+      fs.write(path, 'delete me')
+      bufferToDelete = new Buffer(path)
+
+      expect(bufferToDelete.getPath()).toBe path
       expect(bufferToDelete.isModified()).toBeFalsy()
+
       fs.remove(path)
-      waitsFor "file to be removed", (done) ->
+      waitsFor "file to be removed",  (done) ->
         bufferToDelete.file.one 'remove', done
 
-      runs ->
-        expect(bufferToDelete.getPath()).toBe path
-        expect(bufferToDelete.isModified()).toBeTruthy()
+    it "retains its path and reports the buffer as modified", ->
+      expect(bufferToDelete.getPath()).toBe path
+      expect(bufferToDelete.isModified()).toBeTruthy()
+
+    it "resumes watching of the file when it is re-saved", ->
+      bufferToDelete.save()
+      expect(bufferToDelete.fileExists()).toBeTruthy()
+      expect(bufferToDelete.isInConflict()).toBeFalsy()
+
+      fs.write(path, 'moo')
+
+      waitsFor 'change event', (done) ->
+        bufferToDelete.one 'change', done
 
   describe ".isModified()", ->
     it "returns true when user changes buffer", ->

spec/spec-helper.coffee

@@ -41,7 +41,7 @@ afterEach ->
 
   waits(0)
   runs ->
-    ensureNoPathSubscriptions()
+#     ensureNoPathSubscriptions()
 
 window.keymap.bindKeys '*', 'meta-w': 'close'
 $(document).on 'close', -> window.close()

src/app/buffer.coffee

@@ -94,7 +94,7 @@ class Buffer
 
     @file?.off()
     @file = new File(path)
-    @subscribeToFile()
+    @subscribeToFile() if @file.exists()
 
     @trigger "path-change", this
 
@@ -236,14 +236,18 @@ class Buffer
     @saveAs(@getPath())
 
   saveAs: (path) ->
-    if not path then throw new Error("Can't save buffer with no file path")
+    unless path then throw new Error("Can't save buffer with no file path")
 
     @trigger 'before-save'
-    @cachedDiskContents = @getText()
-    fs.write path, @cachedDiskContents
+
     @file?.updateMd5()
     @setPath(path)
 
+    text = @getText()
+
+    @cachedDiskContents = text
+    @file.write(text)
+    @subscribeToFile()
     @trigger 'after-save'
 
   isModified: ->
@@ -389,4 +393,7 @@ class Buffer
       @trigger 'stopped-changing'
     @stoppedChangingTimeout = setTimeout(stoppedChangingCallback, @stoppedChangingDelay)
 
+  fileExists: ->
+    @file.exists()
+
 _.extend(Buffer.prototype, EventEmitter)

src/app/file.coffee

@@ -9,8 +9,10 @@ class File
   md5: null
 
   constructor: (@path) ->
-    throw "Creating file with path that is not a file: #{@path}" unless fs.isFile(@path)
-    @updateMd5()
+    if @exists() and not fs.isFile(@path)
+      throw new Error(@path + " is a directory")
+
+    @updateMd5() if @exists()
 
   setPath: (@path) ->
 
@@ -19,6 +21,12 @@ class File
   getBaseName: ->
     fs.base(@path)
 
+  write: (text) ->
+    previouslyExisted = @exists()
+    fs.write(@getPath(), text)
+    @updateMd5()
+    @subscribeToNativeChangeEvents() if not previouslyExisted and @subscriptionCount() > 0
+
   exists: ->
     fs.exists(@getPath())
 
@@ -26,7 +34,7 @@ class File
     @md5 = fs.md5ForPath(@path)
 
   afterSubscribe: ->
-    @subscribeToNativeChangeEvents() if @subscriptionCount() == 1
+    @subscribeToNativeChangeEvents() if @exists() and @subscriptionCount() == 1
 
   afterUnsubscribe: ->
     @unsubscribeFromNativeChangeEvents() if @subscriptionCount() == 0
@@ -52,8 +60,8 @@ class File
       @subscribeToNativeChangeEvents()
       @handleNativeChangeEvent("contents-change", @getPath())
     else
+      @unsubscribeFromNativeChangeEvents()
       @trigger "remove"
-      @off()
 
   subscribeToNativeChangeEvents: ->
     @watchId = $native.watchPath @path, (eventType, path) =>