Refollow host when they close last remote editor on guest

lib/guest-portal-binding.js

@@ -71,14 +71,19 @@ class GuestPortalBinding {
   removeEditorProxy (editorProxy) {
     this.lastEditorProxyChangePromise = this.lastEditorProxyChangePromise.then(async () => {
       const editorBinding = this.editorBindingsByEditorProxy.get(editorProxy)
-      editorBinding.dispose()
-
-      await this.toggleEmptyPortalPaneItem()
-
-      const isRetracted = this.portal.resolveFollowState() === FollowState.RETRACTED
-      this.shouldRelayActiveEditorChanges = !isRetracted
-      editorBinding.editor.destroy()
-      this.shouldRelayActiveEditorChanges = true
+      if (editorBinding) {
+        editorBinding.dispose()
+        if (this.editorBindingsByEditorProxy.size === 0) {
+          this.portal.follow(1)
+        }
+
+        await this.toggleEmptyPortalPaneItem()
+
+        const isRetracted = this.portal.resolveFollowState() === FollowState.RETRACTED
+        this.shouldRelayActiveEditorChanges = !isRetracted
+        editorBinding.editor.destroy()
+        this.shouldRelayActiveEditorChanges = true
+      }
     })
 
     return this.lastEditorProxyChangePromise
@@ -137,8 +142,8 @@ class GuestPortalBinding {
       this.editorBindingsByEditorProxy.set(editorProxy, editorBinding)
       this.editorProxiesByEditor.set(editor, editorProxy)
       editorBinding.onDidDispose(() => {
-        this.editorBindingsByEditorProxy.delete(editorProxy)
         this.editorProxiesByEditor.delete(editor)
+        this.editorBindingsByEditorProxy.delete(editorProxy)
       })
 
       this.sitePositionsController.addEditorBinding(editorBinding)
@@ -243,7 +248,9 @@ class GuestPortalBinding {
       this.sitePositionsController.hide()
     }
 
-    if (this.shouldRelayActiveEditorChanges) this.portal.activateEditorProxy(editorProxy)
+    if (this.shouldRelayActiveEditorChanges && paneItem !== this.getEmptyPortalPaneItem()) {
+      this.portal.activateEditorProxy(editorProxy)
+    }
   }
 
   hasPaneItem (paneItem) {

test/guest-portal-binding.test.js

@@ -151,6 +151,30 @@ suite('GuestPortalBinding', () => {
     assert(atomEnv.workspace.getActivePaneItem().getTitle().includes('editor-1'))
   })
 
+  test('host closing last remote editor on guest workspace', async () => {
+    const portal = new FakePortal()
+    const client = {joinPortal: () => portal}
+    const atomEnv = buildAtomEnvironment()
+    const portalBinding = buildGuestPortalBinding(client, atomEnv, 'some-portal')
+
+    await portalBinding.initialize()
+    portal.setFollowState(FollowState.RETRACTED)
+
+    const editorProxy1 = new FakeEditorProxy('editor-1')
+    await portalBinding.updateTether(FollowState.RETRACTED, editorProxy1)
+
+    const editorProxy2 = new FakeEditorProxy('editor-2')
+    portal.setFollowState(FollowState.DISCONNECTED)
+    await portalBinding.updateTether(FollowState.DISCONNECTED)
+
+    await portalBinding.removeEditorProxy(editorProxy2)
+    assert.equal(portal.resolveFollowState(), FollowState.DISCONNECTED)
+
+    await portalBinding.removeEditorProxy(editorProxy1)
+    assert.equal(portal.getFollowedSiteId(), 1)
+    assert.equal(portal.resolveFollowState(), FollowState.RETRACTED)
+  })
+
   test('toggling site position components visibility when switching tabs', async () => {
     const stubPubSubGateway = {}
     const client = new TeletypeClient({pubSubGateway: stubPubSubGateway})