Bugfix: Don't clear selections after running an x command w/ no matches

Operations now return a range to select rather than actually performing a selection in `execute`. This allows the composite command to aggregate all ranges to select and only change the selection if it's non empty. Before we had to clear the selections ahead of time and then rely on each operation to imperatively add its selection. This is easier to control. It also ensures that when we execute a previewed operation, we don't add a selection but instead change the selection.

spec/extensions/command-interpreter-spec.coffee

@@ -232,6 +232,16 @@ describe "CommandInterpreter", ->
           expect(selections[2].getBufferRange()).toEqual [[6,34], [6,41]]
           expect(selections[3].getBufferRange()).toEqual [[6,56], [6,63]]
 
+    describe "when nothing is matched", ->
+      it "preserves the existing selection", ->
+        previousSelections = null
+        waitsForPromise ->
+          previousSelections = editSession.getSelectedBufferRanges()
+          interpreter.eval(',x/this will match nothing', editSession)
+
+        runs ->
+          expect(editSession.getSelectedBufferRanges()).toEqual previousSelections
+
   describe "substitution", ->
     it "does nothing if there are no matches", ->
       waitsForPromise ->
@@ -333,7 +343,7 @@ describe "CommandInterpreter", ->
         expect(operations.length).toBeGreaterThan 3
         for operation in operations
           editSession = project.buildEditSessionForPath(operation.getPath())
-          operation.execute(editSession)
+          editSession.setSelectedBufferRange(operation.execute(editSession))
           expect(editSession.getSelectedText()).toMatch /a+/
           editSession.destroy()
           operation.destroy()

src/extensions/command-panel/commands/composite-command.coffee

@@ -24,10 +24,13 @@ class CompositeCommand
         if currentCommand.previewOperations
           deferred.resolve(operations)
         else
-          editSession?.clearAllSelections() unless currentCommand.preserveSelections
+          bufferRanges = []
           for operation in operations
-            operation.execute(editSession)
+            bufferRange = operation.execute(editSession)
+            bufferRanges.push(bufferRange) if bufferRange
             operation.destroy()
+          if bufferRanges.length and not currentCommand.preserveSelections
+            editSession.setSelectedBufferRanges(bufferRanges)
           deferred.resolve()
 
     deferred.promise()

src/extensions/command-panel/operation.coffee

@@ -14,7 +14,7 @@ class Operation
 
   execute: (editSession) ->
     @buffer.change(@getBufferRange(), @newText) if @newText
-    editSession.addSelectionForBufferRange(@getBufferRange()) unless @preserveSelection
+    @getBufferRange() unless @preserveSelection
 
   preview: ->
     range = @anchorRange.getBufferRange()

src/extensions/command-panel/preview-list.coffee

@@ -58,7 +58,8 @@ class PreviewList extends View
   executeSelectedOperation: ->
     operation = @getSelectedOperation()
     editSession = @rootView.open(operation.getPath())
-    operation.execute(editSession)
+    bufferRange = operation.execute(editSession)
+    editSession.setSelectedBufferRange(bufferRange) if bufferRange
     @rootView.focus()
     false