Add initial version of analytics and crash reporting package.

pkg/telemetry/lib/crash_reporting.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:http/http.dart' as http;
+import 'package:stack_trace/stack_trace.dart';
+import 'package:usage/usage.dart';
+
+/// Tells crash backend that this is a Dart error as opposed to, say, Java.
+const String _dartTypeId = 'DartError';
+
+/// Crash backend host.
+const String _crashServerHost = 'clients2.google.com';
+
+/// Path to the crash servlet.
+const String _crashEndpointPath = '/cr/report'; // or, staging_report
+
+/// The field corresponding to the multipart/form-data file attachment where
+/// crash backend expects to find the Dart stack trace.
+const String _stackTraceFileField = 'DartError';
+
+/// The name of the file attached as [stackTraceFileField].
+///
+/// The precise value is not important. It is ignored by the crash back end, but
+/// it must be supplied in the request.
+const String _stackTraceFilename = 'stacktrace_file';
+
+/// Sends crash reports to Google.

[Brian Wilkerson, 2017/06/23 21:41:09]

If we might publish this as a package someday, consider adding a disclaimer
stating that clients aren't allowed to extend, mixin or implement this class, or
make this an interface with a factory constructor that creates an internally
defined class.

[devoncarew, 2017/06/26 15:53:46]

Done.

+class CrashReportSender {

[kevmoo, 2017/06/23 21:01:04]

Should likely have a way to close/dispose this – and propagate that close to
_httpClient

Otherwise, processes can hang...

[devoncarew, 2017/06/26 15:53:46]

Good point! Added a dispose() method, doc'd it, and had it call through to
http.Client.close().

+  static final Uri _baseUri = new Uri(
+      scheme: 'https',
+      host: _crashServerHost,
+      port: 443,

[kevmoo, 2017/06/23 21:01:04]

A bit redundant w/ https?

[devoncarew, 2017/06/26 15:53:46]

removed

+      path: _crashEndpointPath);
+
+  final Analytics analytics;
+
+  http.Client _httpClient;

[kevmoo, 2017/06/23 21:01:05]

make final?

[Brian Wilkerson, 2017/06/23 21:41:09]

It can't be because of the assignment on line 46.

[kevmoo, 2017/06/23 21:43:31]

That can be done in the initializer. No worries.

[devoncarew, 2017/06/26 15:53:46]

refactored to allow final

+
+  /// Create a new [CrashReportSender], using the data from the given
+  /// [Analytics] instance.
+  CrashReportSender(this.analytics, {http.Client httpClient}) {
+    _httpClient = httpClient ?? new http.Client();
+  }
+
+  /// Sends one crash report.
+  ///
+  /// The report is populated from data in [error] and [stackTrace].
+  Future sendReport(dynamic error, [StackTrace stackTrace]) async {

[Brian Wilkerson, 2017/06/23 21:41:09]

Consider making stackTrace a named parameter. Adding more parameters in the
future will be cleaner.

[devoncarew, 2017/06/26 15:53:46]

Makes sense, will do.

+    if (!analytics.enabled) {
+      return;
+    }
+
+    try {
+      final Uri uri = _baseUri.replace(
+        queryParameters: <String, String>{
+          'product': analytics.trackingId,
+          'version': analytics.applicationVersion,
+        },
+      );
+
+      final http.MultipartRequest req = new http.MultipartRequest('POST', uri);
+      req.fields['uuid'] = analytics.clientId;
+      req.fields['product'] = analytics.trackingId;
+      req.fields['version'] = analytics.applicationVersion;
+      req.fields['osName'] = Platform.operatingSystem;
+      req.fields['osVersion'] = Platform.operatingSystem; // includes the vesion

[Brian Wilkerson, 2017/06/23 21:41:09]

"vesion" --> "version"

Should we parse out the name and version?

[devoncarew, 2017/06/26 15:53:45]

On investigation, this field does not contain the operating system version (as
text or otherwise) :(

I filed https://github.com/dart-lang/sdk/issues/30018 to be able to get this
info.

+      req.fields['type'] = _dartTypeId;
+      req.fields['error_runtime_type'] = '${error.runtimeType}';
+
+      final Chain chain = new Chain.parse(stackTrace.toString());
+      req.files.add(new http.MultipartFile.fromString(
+          _stackTraceFileField, chain.terse.toString(),
+          filename: _stackTraceFilename));
+
+      final http.StreamedResponse resp = await _httpClient.send(req);
+
+      if (resp.statusCode != 200) {
+        throw 'server responded with HTTP status code ${resp.statusCode}';
+      }
+    } catch (sendError, sendStackTrace) {

[kevmoo, 2017/06/23 21:01:04]

A tiny more conventional to use `on SocketException` then another blank catch

Also: good to avoid just throwing `String`

[devoncarew, 2017/06/26 15:53:45]

Done.

+      if (sendError is SocketException) {
+        throw 'network error while sending crash report: $sendError';
+      } else {
+        // If the sender itself crashes, just print.
+        throw 'exception while sending crash report: $sendError\n$sendStackTrace';

[kevmoo, 2017/06/23 21:01:05]

long line

[devoncarew, 2017/06/26 15:53:46]

Done.

+      }
+    }
+  }
+}