When insertion of text during autocomplete results in no matches, automatically select current match and insert the inserted text after it

spec/app/autocomplete-spec.coffee

@@ -190,23 +190,39 @@ describe "Autocomplete", ->
           expect(autocomplete.buildWordList).not.toHaveBeenCalled()
 
       describe "when the change was not caused by autocomplete", ->
-        it "rebuilds the match list based on the new prefix and suffix", ->
-          editor.buffer.insert([10, 0] ,"t")
-          editor.setCursorBufferPosition [10, 0]
-          editor.trigger "autocomplete:toggle"
-          expect($(document).find('#autocomplete')).toExist()
+        describe "when the change produces a prefix that still has matches in the word list", ->
+          it "rebuilds the match list based on the new prefix and suffix", ->
+            editor.buffer.insert([10, 0] ,"t")
+            editor.setCursorBufferPosition [10, 0]
+            editor.trigger "autocomplete:toggle"
+            expect($(document).find('#autocomplete')).toExist()
 
-          editor.insertText('c')
+            editor.insertText('c')
 
-          expect($(document).find('#autocomplete')).toExist()
+            expect($(document).find('#autocomplete')).toExist()
 
-          expect(editor.lineForBufferRow(10)).toBe "current"
-          expect(editor.getCursorBufferPosition()).toEqual [10,6]
-          expect(editor.getSelection().getBufferRange()).toEqual [[10,1], [10,6]]
+            expect(editor.lineForBufferRow(10)).toBe "current"
+            expect(editor.getCursorBufferPosition()).toEqual [10,6]
+            expect(editor.getSelection().getBufferRange()).toEqual [[10,1], [10,6]]
 
-          expect(autocomplete.matchesList.find('li').length).toBe 2
-          expect(autocomplete.matchesList.find('li:eq(0)')).toHaveText('current')
-          expect(autocomplete.matchesList.find('li:eq(1)')).toHaveText('concat')
+            expect(autocomplete.matchesList.find('li').length).toBe 2
+            expect(autocomplete.matchesList.find('li:eq(0)')).toHaveText('current')
+            expect(autocomplete.matchesList.find('li:eq(1)')).toHaveText('concat')
+
+        describe "when the change produces a prefix that has no matches in the word list", ->
+          it "accepts the selected match and appends the change after it", ->
+            editor.buffer.insert([10, 0] ,"c")
+            editor.setCursorBufferPosition [10, 1]
+            editor.trigger "autocomplete:toggle"
+            expect($(document).find('#autocomplete')).toExist()
+
+            editor.insertText(' ')
+
+            expect(editor.lineForBufferRow(10)).toBe "current "
+            expect(editor.getCursorBufferPosition()).toEqual [10,8]
+            expect(editor.getSelection().getBufferRange()).toEqual [[10,8], [10,8]]
+
+            expect($(document).find('#autocomplete')).not.toExist()
 
   describe "when editor's buffer is assigned a new buffer", ->
     it 'creates and uses a new word list based on new buffer', ->

src/app/autocomplete.coffee

@@ -37,7 +37,7 @@ class Autocomplete extends View
     @currentBuffer = buffer
     @buildWordList()
 
-    @currentBuffer.on 'change.autocomplete', => @bufferChanged()
+    @currentBuffer.on 'change.autocomplete', (e) => @bufferChanged(e)
 
   cancel: ->
     @detach()
@@ -86,13 +86,27 @@ class Autocomplete extends View
     nextIndex = (@currentMatchIndex + 1) % @matches.length
     @selectMatch(nextIndex)
 
-  bufferChanged: ->
-    @buildMatchList() if @parent()[0] and not @isAutocompleting
+  bufferChanged: (e) ->
+    if @parent()[0] and not @isAutocompleting
+      selectedMatch = @selectedMatch()
+      @buildMatchList()
+      if @matches.length == 0
+        @detach()
+        @currentBuffer.undo()
+        @completeUsingMatch(selectedMatch)
+        @editor.getSelection().clearSelection()
+        @editor.insertText(e.newText)
+        return
+
     @buildWordList() unless @isAutocompleting
 
   buildMatchList: ->
     selection = @editor.getSelection()
     {prefix, suffix} = @prefixAndSuffixOfSelection(selection)
+    if (prefix.length + suffix.length) == 0
+      @matches = []
+      return
+
     currentWord = prefix + @editor.getSelectedText() + suffix
 
     @matches = (match for match in @wordMatches(prefix, suffix) when match[0] != currentWord)
@@ -121,10 +135,12 @@ class Autocomplete extends View
     @currentMatchIndex = index
     @matchesList.find("li").removeClass "selected"
     @matchesList.find("li:eq(#{index})").addClass "selected"
-    @completeUsingMatch(index)
+    @completeUsingMatch(@selectedMatch())
 
-  completeUsingMatch: (matchIndex) ->
-    match = @matches[matchIndex]
+  selectedMatch: ->
+    @matches[@currentMatchIndex]
+
+  completeUsingMatch: (match) ->
     selection = @editor.getSelection()
     startPosition = selection.getBufferRange().start
     @isAutocompleting = true