Fix backspacing into a block from offset 0 in Firefox

src/trix/models/composition.coffee

@@ -1,7 +1,7 @@
 #= require trix/models/document
 #= require trix/models/line_break_insertion
 
-{normalizeRange, rangesAreEqual, objectsAreEqual, arrayStartsWith, summarizeArrayChange, getAllAttributeNames, getBlockConfig, getTextConfig, extend} = Trix
+{normalizeRange, rangesAreEqual, rangeIsCollapsed, objectsAreEqual, arrayStartsWith, summarizeArrayChange, getAllAttributeNames, getBlockConfig, getTextConfig, extend} = Trix
 
 class Trix.Composition extends Trix.BasicObject
   constructor: ->
@@ -118,23 +118,26 @@ class Trix.Composition extends Trix.BasicObject
     @insertText(text)
 
   deleteInDirection: (direction) ->
-    range = [startPosition, endPosition] = @getSelectedRange()
+    range = @getSelectedRange()
+    selectionIsCollapsed = rangeIsCollapsed(range)
     block = @getBlock()
 
-    if startPosition is endPosition
-      startLocation = @document.locationFromPosition(startPosition)
-      if direction is "backward" and startLocation.offset is 0
-        if @canDecreaseBlockAttributeLevel()
-          if block.isListItem()
-            @decreaseListLevel()
-          else
-            @decreaseBlockAttributeLevel()
+    if selectionIsCollapsed and direction is "backward"
+      {offset} = @document.locationFromPosition(range[0])
+      deletingIntoPreviousBlock = offset is 0
 
-          @setSelection(startPosition)
-          return if block.isEmpty()
+    if deletingIntoPreviousBlock
+      if @canDecreaseBlockAttributeLevel()
+        if block.isListItem()
+          @decreaseListLevel()
+        else
+          @decreaseBlockAttributeLevel()
 
-      range = @getExpandedRangeInDirection(direction)
+        @setSelection(range[0])
+        return false if block.isEmpty()
 
+    if selectionIsCollapsed
+      range = @getExpandedRangeInDirection(direction)
       if direction is "backward"
         attachment = @getAttachmentAtRange(range)
 
@@ -144,7 +147,7 @@ class Trix.Composition extends Trix.BasicObject
     else
       @setDocument(@document.removeTextAtRange(range))
       @setSelection(range[0])
-      false if block.isListItem()
+      false if deletingIntoPreviousBlock
 
   moveTextFromRange: (range) ->
     [position] = @getSelectedRange()

src/trix/observers/mutation_observer.coffee

@@ -1,4 +1,4 @@
-{defer, findClosestElementFromNode, nodeIsEmptyTextNode, normalizeSpaces, summarizeStringChange, tagName} = Trix
+{defer, findClosestElementFromNode, nodeIsEmptyTextNode, nodeIsBlockStartComment, normalizeSpaces, summarizeStringChange, tagName} = Trix
 
 class Trix.MutationObserver extends Trix.BasicObject
   mutableAttributeName = "data-trix-mutable"
@@ -82,12 +82,24 @@ class Trix.MutationObserver extends Trix.BasicObject
     mutation for mutation in @mutations when mutation.type is type
 
   getTextChangesFromChildList: ->
-    textAdded = []
-    textRemoved = []
-
-    for {addedNodes, removedNodes} in @getMutationsByType("childList")
-      textAdded.push(getTextForNodes(addedNodes)...)
-      textRemoved.push(getTextForNodes(removedNodes)...)
+    addedNodes = []
+    removedNodes = []
+
+    for mutation in @getMutationsByType("childList")
+      addedNodes.push(mutation.addedNodes...)
+      removedNodes.push(mutation.removedNodes...)
+
+    singleBlockCommentRemoved =
+      addedNodes.length is 0 and
+        removedNodes.length is 1 and
+        nodeIsBlockStartComment(removedNodes[0])
+
+    if singleBlockCommentRemoved
+      textAdded = []
+      textRemoved = ["\n"]
+    else
+      textAdded = getTextForNodes(addedNodes)
+      textRemoved = getTextForNodes(removedNodes)
 
     additions: (normalizeSpaces(text) for text, index in textAdded when text isnt textRemoved[index])
     deletions: (normalizeSpaces(text) for text, index in textRemoved when text isnt textAdded[index])

test/src/system/mutation_input_test.coffee

@@ -46,6 +46,18 @@ testGroup "Mutation input", template: "editor_empty", ->
         assert.locationRange index: 0, offset: 0
         expectDocument("\n")
 
+  test "backspacing a block comment node", (expectDocument) ->
+    element = getEditorElement()
+    element.editor.loadHTML("""<blockquote>a</blockquote><div>b</div>""")
+    defer ->
+      element.editor.setSelectedRange(2)
+      triggerEvent(element, "keydown", charCode: 0, keyCode: 8, which: 8)
+      commentNode = element.lastChild.firstChild
+      commentNode.parentNode.removeChild(commentNode)
+      defer ->
+        assert.locationRange index: 0, offset: 1
+        expectDocument("ab\n")
+
   test "typing formatted text with autocapitalization on", (expectDocument) ->
     element = getEditorElement()