Add sourcePath parameter to StyleManager::addStyleSheet

spec/style-manager-spec.coffee

@@ -7,12 +7,18 @@ describe "StyleManager", ->
     manager = new StyleManager
 
   describe "::addStyleSheet(source, params)", ->
-    it "adds a stylesheet based on the given source and returns a disposable allowing it to be removed", ->
+    [addEvents, removeEvents, updateEvents] = []
+
+    beforeEach ->
       addEvents = []
       removeEvents = []
+      updateEvents = []
+
       manager.onDidAddStyleSheet (event) -> addEvents.push(event)
       manager.onDidRemoveStyleSheet (event) -> removeEvents.push(event)
+      manager.onDidUpdateStyleSheet (event) -> updateEvents.push(event)
 
+    it "adds a stylesheet based on the given source and returns a disposable allowing it to be removed", ->
       disposable = manager.addStyleSheet("a {color: red;}")
 
       expect(addEvents.length).toBe 1
@@ -27,3 +33,26 @@ describe "StyleManager", ->
       expect(removeEvents.length).toBe 1
       expect(removeEvents[0].styleElement.textContent).toBe "a {color: red;}"
       expect(manager.getStyleElements().length).toBe 0
+
+    describe "when a sourcePath parameter is specified", ->
+      it "ensures a maximum of one style element for the given source path, updating a previous if it exists", ->
+        disposable1 = manager.addStyleSheet("a {color: red;}", sourcePath: '/foo/bar')
+
+        expect(addEvents.length).toBe 1
+        expect(addEvents[0].sourcePath).toBe '/foo/bar'
+
+        disposable2 = manager.addStyleSheet("a {color: blue;}", sourcePath: '/foo/bar')
+
+        expect(addEvents.length).toBe 1
+        expect(updateEvents.length).toBe 1
+        expect(updateEvents[0].sourcePath).toBe '/foo/bar'
+        expect(updateEvents[0].styleElement.textContent).toBe "a {color: blue;}"
+
+        disposable2.dispose()
+        addEvents = []
+
+        manager.addStyleSheet("a {color: yellow;}", sourcePath: '/foo/bar')
+
+        expect(addEvents.length).toBe 1
+        expect(addEvents[0].sourcePath).toBe '/foo/bar'
+        expect(addEvents[0].styleElement.textContent).toBe "a {color: yellow;}"

src/style-manager.coffee

@@ -5,6 +5,7 @@ class StyleManager
   constructor: ->
     @emitter = new Emitter
     @styleElements = []
+    @styleElementsBySourcePath = {}
 
   onDidAddStyleSheet: (callback) ->
     @emitter.on 'did-add-style-sheet', callback
@@ -12,19 +13,35 @@ class StyleManager
   onDidRemoveStyleSheet: (callback) ->
     @emitter.on 'did-remove-style-sheet', callback
 
+  onDidUpdateStyleSheet: (callback) ->
+    @emitter.on 'did-update-style-sheet', callback
+
   getStyleElements: ->
     @styleElements.slice()
 
-  addStyleSheet: (source) ->
-    styleElement = document.createElement('style')
+  addStyleSheet: (source, params) ->
+    sourcePath = params?.sourcePath
+    if sourcePath? and styleElement = @styleElementsBySourcePath[sourcePath]
+      updated = true
+    else
+      styleElement = document.createElement('style')
+
     styleElement.textContent = source
+
     @styleElements.push(styleElement)
-    @emitter.emit 'did-add-style-sheet', {styleElement}
+    @styleElementsBySourcePath[sourcePath] ?= styleElement if sourcePath?
 
-    new Disposable => @removeStyleElement(styleElement)
+    if updated
+      @emitter.emit 'did-update-style-sheet', {styleElement, sourcePath}
+    else
+      @emitter.emit 'did-add-style-sheet', {styleElement, sourcePath}
 
-  removeStyleElement: (styleElement) ->
+    new Disposable => @removeStyleElement(styleElement, params)
+
+  removeStyleElement: (styleElement, params) ->
     index = @styleElements.indexOf(styleElement)
     unless index is -1
       @styleElements.splice(index, 1)
+      sourcePath = params?.sourcePath
+      delete @styleElementsBySourcePath[sourcePath] if sourcePath?
       @emitter.emit 'did-remove-style-sheet', {styleElement}