Only emit did-update when there are changes; set consistent classes on error

lib/buffer-search.js

@@ -237,7 +237,7 @@ class BufferSearch {
       }
     }
 
-    this.emitter.emit('did-update', this.markers.slice());
+    if (changes.length) this.emitter.emit('did-update', this.markers.slice());
     this.currentResultMarker = null;
     this.setCurrentMarkerFromSelection();
   }

lib/find-view.coffee

@@ -307,7 +307,6 @@ class FindView extends View
       atom.beep()
 
   markersUpdated: (@markers) =>
-    @findError = null
     @updateResultCounter()
     @updateReplaceEnablement()
 
@@ -342,6 +341,8 @@ class FindView extends View
     @descriptionLabel.text(infoMessage).removeClass('text-error')
 
   setErrorMessage: (errorMessage) ->
+    this.removeClass('has-results')
+    this.addClass('has-no-results')
     @descriptionLabel.text(errorMessage).addClass('text-error')
 
   clearMessage: ->

spec/find-view-spec.coffee

@@ -506,6 +506,29 @@ describe 'FindView', ->
             expect(findView.descriptionLabel).toHaveClass 'text-error'
             expect(findView.descriptionLabel.text()).toContain 'Invalid regular expression'
 
+          it "does not reset when the buffer is updated", ->
+            # This is a rather specific test: the error message only disappeared
+            # when there were no changes. Backspacing nothing can reproduce this,
+            # as well as saving or undoing and then redoing.
+            editor.setCursorBufferPosition([0, 0])
+            # Since we're at the beginning of the file, backspacing will do nothing but still send a change event
+            editor.backspace()
+            advanceClock(editor.buffer.stoppedChangingDelay)
+
+            expect(findView.descriptionLabel).toHaveClass 'text-error'
+            expect(findView.descriptionLabel.text()).toContain 'Invalid regular expression'
+
+          it "adds the has-no-results class", ->
+            findView.findEditor.setText 'it'
+            atom.commands.dispatch(findView.findEditor.element, 'core:confirm')
+            expect(findView).toHaveClass 'has-results'
+            expect(findView).not.toHaveClass 'has-no-results'
+
+            findView.findEditor.setText 'i[t'
+            atom.commands.dispatch(findView.findEditor.element, 'core:confirm')
+            expect(findView).toHaveClass 'has-no-results'
+            expect(findView).not.toHaveClass 'has-results'
+
           it "will be reset when there is no longer an error", ->
             expect(findView.descriptionLabel).toHaveClass 'text-error'