From da992a527c6f0c6998799ea1616cce5bac28be98 Mon Sep 17 00:00:00 2001
From: Eric Hwang <e@lever.co>
Date: Wed, 5 Jun 2024 15:12:51 -0700
Subject: [PATCH] Add new App event 'page', emitted when a new Page instance is
 created

---
 package.json          |  1 +
 src/App.ts            | 16 ++++++++--------
 src/AppForServer.ts   |  1 +
 test/all/App.mocha.js | 42 ++++++++++++++++++++++++++++++++++++++----
 4 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/package.json b/package.json
index 5febdbfb..540c59f7 100644
--- a/package.json
+++ b/package.json
@@ -77,6 +77,7 @@
     "mocha": "^10.0.0",
     "prettier": "^3.0.1",
     "racer": "^v2.0.0-beta.11",
+    "sinon": "^18.0.0",
     "ts-node": "^10.9.2",
     "typescript": "~5.1.3"
   },
diff --git a/src/App.ts b/src/App.ts
index 98b5504b..51ea96b7 100644
--- a/src/App.ts
+++ b/src/App.ts
@@ -51,14 +51,13 @@ type Routes = [string, string, any][];
  * APP EVENTS
  *
   'error', Error
-  'pageRendered', Page
-  'destroy'
-  'model', Model
-  'route', Page
-  'routeDone', Page, transition: boolean
-  'ready', Page
-  'load', Page
-  'destroyPage', Page
+  'model', Model - a new root model was created by the app, server and client
+  'page', Page - a new Page was created by the app, server and client
+  'ready', Page - app is ready to attach to server-rendered HTML, client only
+  'load', Page - app is fully loaded, client only
+  'destroyPage', Page - current Page is about to be destroyed, client only
+  'route', Page - app is about to invoke a route handler, client only
+  'routeDone', Page, routeType - app has finished running a route handler, client only
  */
 
 export abstract class App extends EventEmitter {
@@ -427,6 +426,7 @@ export class AppForClient extends App {
     const ClientPage = this.Page as unknown as typeof PageForClient;
     const page = new ClientPage(this, this.model);
     this.page = page;
+    this.emit('page', page);
     return page;
   }
 
diff --git a/src/AppForServer.ts b/src/AppForServer.ts
index 91bdc284..e591ee7e 100644
--- a/src/AppForServer.ts
+++ b/src/AppForServer.ts
@@ -159,6 +159,7 @@ export class AppForServer extends App {
       });
       page.on('error', next);
     }
+    this.emit('page', page);
     return page;
   }
 
diff --git a/test/all/App.mocha.js b/test/all/App.mocha.js
index 9c877a8f..6c9a5c79 100644
--- a/test/all/App.mocha.js
+++ b/test/all/App.mocha.js
@@ -1,14 +1,48 @@
-var expect = require('chai').expect;
-var AppForClient = require('../../src/App').AppForClient;
+const expect = require('chai').expect;
+const racer = require('racer');
+const sinon = require('sinon');
+const AppForClient = require('../../src/App').AppForClient;
+const { DerbyForClient } = require('../../src/Derby');
+const { DerbyForServer } = require('../../src/DerbyForServer');
+
+describe('App', () => {
+  afterEach(() => {
+    sinon.restore();
+  });
+
+  [DerbyForClient, DerbyForServer].forEach((DerbyClass) => {
+    describe(`from ${DerbyClass.name}`, () => {
+      it('createPage emits \'page\' event with newly created page', () => {
+        const derby = new DerbyClass();
+        // A properly working _init() requires a more complicated setup,
+        // especially for AppForClient, so stub it out since createPage()
+        // doesn't depend on anything in _init().
+        sinon.stub(derby.App.prototype, '_init');
+
+        const app = derby.createApp();
+        app.model = racer.createModel();
+
+        let pageFromEvent = null;
+        app.on('page', (page) => {
+          pageFromEvent = page;
+        });
+        const page1 = app.createPage({});
+        expect(pageFromEvent).to.equal(page1);
+        const page2 = app.createPage({});
+        expect(pageFromEvent).to.equal(page2);
+      });
+    });
+  });
+});
 
 describe('App._parseInitialData', () => {
   it('parses simple json', () => {
-    var actual = AppForClient._parseInitialData('{"foo": "bar"}');
+    const actual = AppForClient._parseInitialData('{"foo": "bar"}');
     expect(actual).to.deep.equal({ foo: 'bar' });
   });
 
   it('parses escaped json', () => {
-    var actual = AppForClient._parseInitialData('{"foo": "<\\u0021bar><\\/bar>"}');
+    const actual = AppForClient._parseInitialData('{"foo": "<\\u0021bar><\\/bar>"}');
     expect(actual).to.deep.equal({ foo: '<!bar></bar>' });
   });