Resize dock to fit on double-click of resize handle

spec/dock-spec.js

@@ -1,3 +1,7 @@
+/** @babel */
+
+import {it, fit, ffit, fffit, beforeEach, afterEach} from './async-spec-helpers'
+
 describe('Dock', () => {
   describe('when a pane in a dock is activated', () => {
     it('opens the dock', () => {
@@ -12,4 +16,72 @@ describe('Dock', () => {
       expect(atom.workspace.getLeftDock().isOpen()).toBe(true)
     })
   })
-})
+
+  describe('when the dock resize handle is double-clicked', () => {
+    describe('when the dock is open', () => {
+      it('resizes a vertically-oriented dock to the current item\'s preferred width', async () => {
+        const workspaceElement = atom.views.getView(atom.workspace)
+        jasmine.attachToDOM(workspaceElement)
+
+        const item = {
+          element: document.createElement('div'),
+          getDefaultLocation() { return 'left' },
+          getPreferredWidth() { return 142 },
+          getPreferredHeight() { return 122 }
+        }
+
+        await atom.workspace.open(item)
+        const dock = atom.workspace.getLeftDock()
+        const dockElement = dock.getElement()
+
+        dock.setState({size: 300})
+        expect(dockElement.offsetWidth).toBe(300)
+        dockElement.querySelector('.atom-dock-resize-handle').dispatchEvent(new MouseEvent('mousedown', {detail: 2}))
+
+        expect(dockElement.offsetWidth).toBe(item.getPreferredWidth())
+      })
+
+      it('resizes a horizontally-oriented dock to the current item\'s preferred width', async () => {
+        const workspaceElement = atom.views.getView(atom.workspace)
+        jasmine.attachToDOM(workspaceElement)
+
+        const item = {
+          element: document.createElement('div'),
+          getDefaultLocation() { return 'bottom' },
+          getPreferredWidth() { return 122 },
+          getPreferredHeight() { return 142 }
+        }
+
+        await atom.workspace.open(item)
+        const dock = atom.workspace.getBottomDock()
+        const dockElement = dock.getElement()
+
+        dock.setState({size: 300})
+        expect(dockElement.offsetHeight).toBe(300)
+        dockElement.querySelector('.atom-dock-resize-handle').dispatchEvent(new MouseEvent('mousedown', {detail: 2}))
+
+        expect(dockElement.offsetHeight).toBe(item.getPreferredHeight())
+      })
+    })
+
+    describe('when the dock is closed', () => {
+      it('does nothing', async () => {
+        const workspaceElement = atom.views.getView(atom.workspace)
+        jasmine.attachToDOM(workspaceElement)
+
+        const item = {
+          element: document.createElement('div'),
+          getDefaultLocation() { return 'bottom' },
+          getPreferredWidth() { return 122 },
+          getPreferredHeight() { return 142 }
+        }
+
+        await atom.workspace.open(item, {activatePane: false})
+
+        const dockElement = atom.workspace.getBottomDock().getElement()
+        dockElement.querySelector('.atom-dock-resize-handle').dispatchEvent(new MouseEvent('mousedown', {detail: 2}))
+        expect(dockElement.offsetHeight).toBe(0)
+      })
+    })
+  })
+})