Polyfill the fetch Headers object if needed (#1014)

* test: improve test description

* fix: polyfill the fetch Headers object if needed

src/browser/telemetry.js

@@ -1,4 +1,5 @@
 var _ = require('../utility');
+var headers = require('../utility/headers');
 var scrub = require('../scrub');
 var urlparser = require('./url');
 var domUtil = require('./domUtility');
@@ -362,7 +363,7 @@ Instrumenter.prototype.instrumentNetwork = function() {
         if (args[1] && args[1].headers) {
           // Argument may be a Headers object, or plain object. Ensure here that
           // we are working with a Headers object with case-insensitive keys.
-          var reqHeaders = new Headers(args[1].headers);
+          var reqHeaders = headers(args[1].headers);
 
           metadata.request_content_type = reqHeaders.get('Content-Type');
 

src/utility/headers.js

@@ -0,0 +1,94 @@
+/*
+ * headers - Detect when fetch Headers are undefined and use a partial polyfill.
+ *
+ * A full polyfill is not used in order to keep package size as small as possible.
+ * Since this is only used internally and is not added to the window object,
+ * the full interface doesn't need to be supported.
+ *
+ * This implementation is modified from whatwg-fetch:
+ * https://github.com/github/fetch
+ */
+function headers(headers) {
+  if (typeof Headers === 'undefined') {
+    return new FetchHeaders(headers);
+  }
+
+  return new Headers(headers);
+}
+
+function normalizeName(name) {
+  if (typeof name !== 'string') {
+    name = String(name)
+  }
+  return name.toLowerCase()
+}
+
+function normalizeValue(value) {
+  if (typeof value !== 'string') {
+    value = String(value)
+  }
+  return value
+}
+
+function iteratorFor(items) {
+  var iterator = {
+    next: function() {
+      var value = items.shift()
+      return {done: value === undefined, value: value}
+    }
+  }
+
+  return iterator
+}
+
+function FetchHeaders(headers) {
+  this.map = {}
+
+  if (headers instanceof FetchHeaders) {
+    headers.forEach(function(value, name) {
+      this.append(name, value)
+    }, this)
+  } else if (Array.isArray(headers)) {
+    headers.forEach(function(header) {
+      this.append(header[0], header[1])
+    }, this)
+  } else if (headers) {
+    Object.getOwnPropertyNames(headers).forEach(function(name) {
+      this.append(name, headers[name])
+    }, this)
+  }
+}
+
+FetchHeaders.prototype.append = function(name, value) {
+  name = normalizeName(name)
+  value = normalizeValue(value)
+  var oldValue = this.map[name]
+  this.map[name] = oldValue ? oldValue + ', ' + value : value
+}
+
+FetchHeaders.prototype.get = function(name) {
+  name = normalizeName(name)
+  return this.has(name) ? this.map[name] : null
+}
+
+FetchHeaders.prototype.has = function(name) {
+  return this.map.hasOwnProperty(normalizeName(name))
+}
+
+FetchHeaders.prototype.forEach = function(callback, thisArg) {
+  for (var name in this.map) {
+    if (this.map.hasOwnProperty(name)) {
+      callback.call(thisArg, this.map[name], name, this)
+    }
+  }
+}
+
+FetchHeaders.prototype.entries = function() {
+  var items = []
+  this.forEach(function(value, name) {
+    items.push([name, value])
+  })
+  return iteratorFor(items)
+}
+
+module.exports = headers;

test/browser.rollbar.test.js

@@ -1606,7 +1606,7 @@ describe('options.autoInstrument', function() {
     })
   });
 
-  it('should add telemetry events for fetch calls', function(done) {
+  it('should report error for http 4xx fetch calls, when enabled', function(done) {
     var server = window.server;
     stubResponse(server);
     server.requests.length = 0;
@@ -1659,6 +1659,74 @@ describe('options.autoInstrument', function() {
     })
   });
 
+  it('should add telemetry headers when fetch Headers object is undefined', function(done) {
+    var server = window.server;
+    stubResponse(server);
+    server.requests.length = 0;
+
+    window.fetchStub = sinon.stub(window, 'fetch');
+
+    var readableStream = new ReadableStream({
+      start(controller) {
+        controller.enqueue(JSON.stringify({name: 'foo', password: '123456'}));
+        controller.close();
+      }
+    });
+
+    window.fetch.returns(Promise.resolve(new Response(
+      readableStream,
+      { status: 200, statusText: 'OK', headers: { 'content-type': 'application/json', 'password': '123456' }}
+    )));
+
+    var options = {
+      accessToken: 'POST_CLIENT_ITEM_TOKEN',
+      autoInstrument: {
+        log: false,
+        network: true,
+        networkResponseHeaders: true,
+        networkRequestHeaders: true
+      }
+    };
+    var rollbar = window.rollbar = new Rollbar(options);
+
+    // Remove Headers from window object
+    var originalHeaders = window.Headers;
+    delete window.Headers;
+
+    const fetchInit = {
+      method: 'POST',
+      headers: {'Content-Type': 'application/json', Secret: '123456'},
+      body: JSON.stringify({name: 'bar', secret: 'xhr post'})
+    };
+    var fetchRequest = new Request('https://example.com/xhr-test');
+    window.fetch(fetchRequest, fetchInit)
+    .then(function(response) {
+      try {
+        rollbar.log('test'); // generate a payload to inspect
+        server.respond();
+
+        expect(server.requests.length).to.eql(1);
+        var body = JSON.parse(server.requests[0].requestBody);
+
+        // Verify request headers capture and case-insensitive scrubbing
+        expect(body.data.body.telemetry[0].body.request_headers).to.eql({'content-type': 'application/json', secret: '********'});
+
+        // Verify response headers capture and case-insensitive scrubbing
+        expect(body.data.body.telemetry[0].body.response.headers).to.eql({'content-type': 'application/json', password: '********'});
+
+        // Assert that the original stream reader hasn't been read.
+        expect(response.bodyUsed).to.eql(false);
+
+        rollbar.configure({ autoInstrument: false });
+        window.fetch.restore();
+        window.Headers = originalHeaders;
+        done();
+      } catch (e) {
+        done(e);
+      }
+    })
+  });
+
   it('should add a diagnostic message when wrapConsole fails', function(done) {
     var server = window.server;
     stubResponse(server);