🐛 Fix error raised on destruction due to remaining decorations

Fixes #273

lib/minimap.coffee

@@ -70,6 +70,7 @@ class Minimap
   # Destroys the model.
   destroy: ->
     @subscriptions.dispose()
+    @removeAllDecorations()
     @textEditor = null
     @emitter.emit 'did-destroy'
     @destroyed = true

lib/mixins/decoration-management.coffee

@@ -105,6 +105,7 @@ class DecorationManagement extends Mixin
   #
   # Returns a `Decoration` object.
   decorateMarker: (marker, decorationParams) ->
+    return if @destroyed
     return unless marker?
     marker = @getMarker(marker.id)
     return unless marker?
@@ -226,6 +227,21 @@ class DecorationManagement extends Mixin
     delete @decorationMarkerChangedSubscriptions[marker.id]
     delete @decorationMarkerDestroyedSubscriptions[marker.id]
 
+  removeAllDecorations: ->
+    sub.dispose() for id,sub of @decorationMarkerChangedSubscriptions
+    sub.dispose() for id,sub of @decorationMarkerDestroyedSubscriptions
+    sub.dispose() for id,sub of @decorationUpdatedSubscriptions
+    sub.dispose() for id,sub of @decorationDestroyedSubscriptions
+    decoration.destroy() for id,decoration of @decorationsById
+
+    @decorationsById = {}
+    @decorationsByMarkerId = {}
+    @decorationMarkerChangedSubscriptions = {}
+    @decorationMarkerDestroyedSubscriptions = {}
+    @decorationUpdatedSubscriptions = {}
+    @decorationDestroyedSubscriptions = {}
+
+
   # Internal: Receive the update event of a decoration and trigger
   # a `minimap:decoration-updated` event.
   #

spec/minimap-spec.coffee

@@ -257,3 +257,17 @@ describe 'Minimap', ->
       it 'creates a change corresponding to the marker range', ->
         expect(changeSpy.calls[1].args[0].start).toEqual(0)
         expect(changeSpy.calls[1].args[0].end).toEqual(0)
+
+    describe 'destroying the minimap', ->
+      beforeEach ->
+        minimap.destroy()
+
+      it 'removes all the previously added decorations', ->
+        expect(minimap.decorationsById).toEqual({})
+        expect(minimap.decorationsByMarkerId).toEqual({})
+
+      it 'prevents the creation of new decorations', ->
+        marker = editor.markBufferRange [[0,6], [0,11]]
+        decoration = minimap.decorateMarker marker, type: 'highlight', class: 'dummy'
+
+        expect(decoration).toBeUndefined()