Merge pull request #7778 from atom/ns-mb-suppress-line-measurement-exceptions

Suppress line measurement exceptions and gather data to solve them

src/atom.coffee

@@ -721,17 +721,12 @@ class Atom extends Model
   Section: Private
   ###
 
-  assert: (condition, message, metadata) ->
+  assert: (condition, message, callback) ->
     return true if condition
 
     error = new Error("Assertion failed: #{message}")
     Error.captureStackTrace(error, @assert)
-
-    if metadata?
-      if typeof metadata is 'function'
-        error.metadata = metadata()
-      else
-        error.metadata = metadata
+    callback?(error)
 
     @emitter.emit 'did-fail-assertion', error
 

src/lines-tile-component.coffee

@@ -346,17 +346,44 @@ class LinesTileComponent
             rangeForMeasurement ?= document.createRange()
             iterator =  document.createNodeIterator(lineNode, NodeFilter.SHOW_TEXT, AcceptFilter)
             textNode = iterator.nextNode()
+            textNodeLength = textNode.length
             textNodeIndex = 0
             nextTextNodeIndex = textNode.textContent.length
 
           while nextTextNodeIndex <= charIndex
             textNode = iterator.nextNode()
+            textNodeLength = textNode.length
             textNodeIndex = nextTextNodeIndex
             nextTextNodeIndex = textNodeIndex + textNode.textContent.length
 
           i = charIndex - textNodeIndex
           rangeForMeasurement.setStart(textNode, i)
-          rangeForMeasurement.setEnd(textNode, i + charLength)
+
+          if i + charLength <= textNodeLength
+            rangeForMeasurement.setEnd(textNode, i + charLength)
+          else
+            rangeForMeasurement.setEnd(textNode, textNodeLength)
+            atom.assert false, "Expected index to be less than the length of text node while measuring", (error) =>
+              editor = @presenter.model
+              screenRow = tokenizedLine.screenRow
+              bufferRow = editor.bufferRowForScreenRow(screenRow)
+
+              error.metadata = {
+                grammarScopeName: editor.getGrammar().scopeName
+                screenRow: screenRow
+                bufferRow: bufferRow
+                softWrapped: editor.isSoftWrapped()
+                softTabs: editor.getSoftTabs()
+                i: i
+                charLength: charLength
+                textNodeLength: textNode.length
+              }
+              error.privateMetadataDescription = "The contents of line #{bufferRow + 1}."
+              error.privateMetadata = {
+                lineText: editor.lineTextForBufferRow(bufferRow)
+              }
+              error.privateMetadataRequestName = "measured-line-text"
+
           charWidth = rangeForMeasurement.getBoundingClientRect().width
           @presenter.setScopedCharacterWidth(scopes, char, charWidth)
 

src/tokenized-buffer.coffee

@@ -296,10 +296,12 @@ 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", =>
-      metadata:
+    atom.assert tokenizedLine?, "TokenizedLine is defined", (error) =>
+      error.metadata = {
         row: row
         rowCount: @tokenizedLines.length
+      }
+
     return false unless tokenizedLine?
 
     return false if @buffer.isRowBlank(row) or tokenizedLine.isComment()