From 98bb2615adb6815c91efcc59593b49e2ec8c3935 Mon Sep 17 00:00:00 2001
From: Yaniv Efraim <yaniv.efraim@gmail.com>
Date: Thu, 12 Apr 2018 18:26:50 +0300
Subject: [PATCH] feat(Tracing): return a buffer from tracing.stop (#2360)

Fixes #2148
---
 docs/api.md          |  4 ++--
 lib/Tracing.js       | 16 +++++++++++++---
 test/tracing.spec.js | 30 ++++++++++++++++++++++++++++--
 3 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/docs/api.md b/docs/api.md
index 7ce22aadd086d..4f206b8826866 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -1602,7 +1602,7 @@ await page.tracing.stop();
 
 #### tracing.start(options)
 - `options` <[Object]>
-  - `path` <[string]> A path to write the trace file to. **required**
+  - `path` <[string]> A path to write the trace file to.
   - `screenshots` <[boolean]> captures screenshots in the trace.
   - `categories` <[Array]<[string]>> specify custom categories to use instead of default.
 - returns: <[Promise]>
@@ -1610,7 +1610,7 @@ await page.tracing.stop();
 Only one trace can be active at a time per browser.
 
 #### tracing.stop()
-- returns: <[Promise]>
+- returns: <[Promise]<[Buffer]>> Promise which resolves to buffer with trace data.
 
 ### class: Dialog
 
diff --git a/lib/Tracing.js b/lib/Tracing.js
index 6b9a87e55a49e..1bce240b9b8fb 100644
--- a/lib/Tracing.js
+++ b/lib/Tracing.js
@@ -35,7 +35,6 @@ class Tracing {
    */
   async start(options) {
     console.assert(!this._recording, 'Cannot start recording trace while already recording trace.');
-    console.assert(options.path, 'Must specify a path to write trace file to.');
 
     const defaultCategories = [
       '-*', 'devtools.timeline', 'v8.execute', 'disabled-by-default-devtools.timeline',
@@ -73,15 +72,26 @@ class Tracing {
    */
   async _readStream(handle, path) {
     let eof = false;
-    const file = await openAsync(path, 'w');
+    let file;
+    if (path)
+      file = await openAsync(path, 'w');
+    const bufs = [];
     while (!eof) {
       const response = await this._client.send('IO.read', {handle});
       eof = response.eof;
+      bufs.push(new Buffer(response.data));
       if (path)
         await writeAsync(file, response.data);
     }
-    await closeAsync(file);
+    if (path)
+      await closeAsync(file);
     await this._client.send('IO.close', {handle});
+    let resultBuffer = null;
+    try {
+      resultBuffer = Buffer.concat(bufs);
+    } finally {
+      return resultBuffer;
+    }
   }
 }
 helper.tracePublicAPI(Tracing);
diff --git a/test/tracing.spec.js b/test/tracing.spec.js
index f41091110afee..00ccc7d6678fe 100644
--- a/test/tracing.spec.js
+++ b/test/tracing.spec.js
@@ -27,8 +27,10 @@ module.exports.addTests = function({testRunner, expect}) {
       state.outputFile = path.join(__dirname, 'assets', `trace-${state.parallelIndex}.json`);
     });
     afterEach(function(state) {
-      fs.unlinkSync(state.outputFile);
-      state.outputFile = null;
+      if (fs.existsSync(state.outputFile)) {
+        fs.unlinkSync(state.outputFile);
+        state.outputFile = null;
+      }
     });
     it('should output a trace', async({page, server, outputFile}) => {
       await page.tracing.start({screenshots: true, path: outputFile});
@@ -52,5 +54,29 @@ module.exports.addTests = function({testRunner, expect}) {
       expect(error).toBeTruthy();
       await page.tracing.stop();
     });
+    it('should return a buffer', async({page, server, outputFile}) => {
+      await page.tracing.start({screenshots: true, path: outputFile});
+      await page.goto(server.PREFIX + '/grid.html');
+      const trace = await page.tracing.stop();
+      const buf = fs.readFileSync(outputFile);
+      expect(trace.toString()).toEqual(buf.toString());
+    });
+    it('should return null in case of Buffer error', async({page, server}) => {
+      await page.tracing.start({screenshots: true});
+      await page.goto(server.PREFIX + '/grid.html');
+      const oldBufferConcat = Buffer.concat;
+      Buffer.concat = bufs => {
+        throw 'error';
+      };
+      const trace = await page.tracing.stop();
+      expect(trace).toEqual(null);
+      Buffer.concat = oldBufferConcat;
+    });
+    it('should support a buffer without a path', async({page, server}) => {
+      await page.tracing.start({screenshots: true});
+      await page.goto(server.PREFIX + '/grid.html');
+      const trace = await page.tracing.stop();
+      expect(trace.toString()).toContain('screenshot');
+    });
   });
 };