Maintain selection directionality when merging selections with keyboard

spec/atom/editor-spec.coffee

@@ -1077,6 +1077,7 @@ describe "Editor", ->
           editor.selectDown()
           expect(editor.compositeSelection.getSelections()).toEqual [selection1]
           expect(selection1.getScreenRange()).toEqual([[0, 9], [4, 25]])
+          expect(selection1.isReversed()).toBeFalsy()
           expect(selection2.parent()).not.toExist()
           expect(selection3.parent()).not.toExist()
 
@@ -1088,6 +1089,7 @@ describe "Editor", ->
           editor.selectUp()
           expect(editor.compositeSelection.getSelections()).toEqual [selection1]
           expect(selection1.getScreenRange()).toEqual([[0, 0], [1, 20]])
+          expect(selection1.isReversed()).toBeTruthy()
           expect(selection2.parent()).not.toExist()
 
         it "merges selections when they intersect when moving left", ->
@@ -1098,6 +1100,7 @@ describe "Editor", ->
           editor.selectLeft()
           expect(editor.compositeSelection.getSelections()).toEqual [selection1]
           expect(selection1.getScreenRange()).toEqual([[0, 8], [1, 20]])
+          expect(selection1.isReversed()).toBeTruthy()
           expect(selection2.parent()).not.toExist()
 
         it "merges selections when they intersect when moving right", ->
@@ -1108,6 +1111,7 @@ describe "Editor", ->
           editor.selectRight()
           expect(editor.compositeSelection.getSelections()).toEqual [selection1]
           expect(selection1.getScreenRange()).toEqual([[0, 9], [1, 21]])
+          expect(selection1.isReversed()).toBeFalsy()
           expect(selection2.parent()).not.toExist()
 
     describe "cursor merging", ->

spec/atom/selection-spec.coffee

@@ -205,3 +205,12 @@ describe "Selection", ->
        editor.setCursorScreenPosition [0,2]
        selection.selectLine(1)
        expect(selection.getText()).toBe "  var sort = function(items) {"
+
+  describe ".isReversed()", ->
+    it "returns true if the cursor precedes the anchor", ->
+      selection.cursor.setScreenPosition([0, 20])
+      selection.selectToScreenPosition([0, 10])
+      expect(selection.isReversed()).toBeTruthy()
+
+      selection.selectToScreenPosition([0, 25])
+      expect(selection.isReversed()).toBeFalsy()

src/atom/composite-selection.coffee

@@ -49,11 +49,11 @@ class CompositeSeleciton
 
   selectLeft: ->
     selection.selectLeft() for selection in @getSelections()
-    @mergeIntersectingSelections()
+    @mergeIntersectingSelections reverse: true
 
   selectUp: ->
     selection.selectUp() for selection in @getSelections()
-    @mergeIntersectingSelections()
+    @mergeIntersectingSelections reverse: true
 
   selectDown: ->
     selection.selectDown() for selection in @getSelections()
@@ -71,14 +71,14 @@ class CompositeSeleciton
   lastSelection: ->
     _.last(@selections)
 
-  mergeIntersectingSelections: ->
+  mergeIntersectingSelections: (options) ->
     for selection in @getSelections()
       otherSelections = @getSelections()
       _.remove(otherSelections, selection)
       for otherSelection in otherSelections
         if selection.intersectsWith(otherSelection)
-          selection.merge(otherSelection)
-          @mergeIntersectingSelections()
+          selection.merge(otherSelection, options)
+          @mergeIntersectingSelections(options)
           return
 
   modifySelectedText: (fn) ->

src/atom/selection.coffee

@@ -139,11 +139,14 @@ class Selection extends View
   isEmpty: ->
     @getBufferRange().isEmpty()
 
+  isReversed: ->
+    @cursor.getBufferPosition().isLessThan(@anchorBufferPosition)
+
   intersectsWith: (otherSelection) ->
     @getScreenRange().intersectsWith(otherSelection.getScreenRange())
 
-  merge: (otherSelection) ->
-    @setScreenRange(@getScreenRange().union(otherSelection.getScreenRange()))
+  merge: (otherSelection, options) ->
+    @setScreenRange(@getScreenRange().union(otherSelection.getScreenRange()), options)
     otherSelection.remove()
 
   remove: ->