Merge pull request #17702 from atom/fb-rh-text-editor-component-updateClassList

Modify TextEditorComponent updateClassList to always add managed classes to element

spec/text-editor-component-spec.js

@@ -818,6 +818,18 @@ describe('TextEditorComponent', () => {
       expect(element.className).toBe('editor a b')
     })
 
+    it('does not blow away class names managed by the component when packages change the element class name', async () => {
+      assertDocumentFocused()
+      const {component, element, editor} = buildComponent({mini: true})
+      element.classList.add('a', 'b')
+      element.focus()
+      await component.getNextUpdatePromise()
+      expect(element.className).toBe('editor mini a b is-focused')
+      element.className = 'a c d';
+      await component.getNextUpdatePromise()
+      expect(element.className).toBe('a c d editor is-focused mini')
+    })
+
     it('ignores resize events when the editor is hidden', async () => {
       const {component, element, editor} = buildComponent({autoHeight: false})
       element.style.height = 5 * component.getLineHeight() + 'px'

src/text-editor-component.js

@@ -848,10 +848,7 @@ class TextEditorComponent {
     }
 
     for (let i = 0; i < newClassList.length; i++) {
-      const className = newClassList[i]
-      if (!oldClassList || !oldClassList.includes(className)) {
-        this.element.classList.add(className)
-      }
+      this.element.classList.add(newClassList[i])
     }
 
     this.classList = newClassList