Maintain change counts for debugging purposes

When we have an unexpected display-buffer or tokenized-buffer state,
we can include the change counts to make sure that every change to the
buffer has been processed by display-buffer and tokenized-buffer. If
they haven’t, there’s something wrong with our event ordering. If they
have, there’s a logic error somewhere else.

package.json

@@ -57,7 +57,7 @@
     "space-pen": "3.8.2",
     "stacktrace-parser": "0.1.1",
     "temp": "0.8.1",
-    "text-buffer": "6.3.8",
+    "text-buffer": "6.3.9",
     "theorist": "^1.0.2",
     "typescript-simple": "1.0.0",
     "underscore-plus": "^1.6.6",

src/display-buffer.coffee

@@ -23,6 +23,7 @@ class DisplayBuffer extends Model
   verticalScrollMargin: 2
   horizontalScrollMargin: 6
   scopedCharacterWidthsChangeCount: 0
+  changeCount: 0
 
   constructor: ({tabLength, @editorWidthInChars, @tokenizedBuffer, buffer, ignoreInvisibles, @largeFileMode}={}) ->
     super
@@ -800,6 +801,11 @@ class DisplayBuffer extends Model
           foldCount: @findFoldMarkers().length
           lastBufferRow: @buffer.getLastRow()
           lastScreenRow: @getLastRow()
+          bufferRow: row
+          screenRow: screenRow
+          displayBufferChangeCount: @changeCount
+          tokenizedBufferChangeCount: @tokenizedBuffer.changeCount
+          bufferChangeCount: @buffer.changeCount
 
       maxBufferColumn = screenLine.getMaxBufferColumn()
       if screenLine.isSoftWrapped() and column > maxBufferColumn
@@ -898,6 +904,9 @@ class DisplayBuffer extends Model
         screenColumn: column
         maxScreenRow: @getLastRow()
         screenLinesDefined: @screenLines.map (sl) -> sl?
+        displayBufferChangeCount: @changeCount
+        tokenizedBufferChangeCount: @tokenizedBuffer.changeCount
+        bufferChangeCount: @buffer.changeCount
       }
       throw error
 
@@ -1179,6 +1188,7 @@ class DisplayBuffer extends Model
     @tokenizedBuffer.rootScopeDescriptor
 
   handleTokenizedBufferChange: (tokenizedBufferChange) =>
+    @changeCount = @tokenizedBuffer.changeCount
     {start, end, delta, bufferChange} = tokenizedBufferChange
     @updateScreenLines(start, end + 1, delta, refreshMarkers: false)
     @setScrollTop(Math.min(@getScrollTop(), @getMaxScrollTop())) if delta < 0

src/tokenized-buffer.coffee

@@ -23,6 +23,7 @@ class TokenizedBuffer extends Model
   invalidRows: null
   visible: false
   configSettings: null
+  changeCount: 0
 
   constructor: ({@buffer, @tabLength, @ignoreInvisibles, @largeFileMode}) ->
     @emitter = new Emitter
@@ -229,6 +230,8 @@ class TokenizedBuffer extends Model
         row + delta
 
   handleBufferChange: (e) ->
+    @changeCount = @buffer.changeCount
+
     {oldRange, newRange} = e
     start = oldRange.start.row
     end = oldRange.end.row
@@ -296,10 +299,12 @@ class TokenizedBuffer extends Model
     # undefined. This should paper over the problem but we want to figure out
     # what is happening:
     tokenizedLine = @tokenizedLineForRow(row)
-    atom.assert tokenizedLine?, "TokenizedLine is defined", (error) =>
+    atom.assert tokenizedLine?, "TokenizedLine is undefined", (error) =>
       error.metadata = {
         row: row
         rowCount: @tokenizedLines.length
+        tokenizedBufferChangeCount: @changeCount
+        bufferChangeCount: @buffer.changeCount
       }
 
     return false unless tokenizedLine?