Better progress reporting.

sdk/lib/_internal/pub/lib/src/progress.dart

Index: sdk/lib/_internal/pub/lib/src/progress.dart
diff --git a/sdk/lib/_internal/pub/lib/src/progress.dart b/sdk/lib/_internal/pub/lib/src/progress.dart
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+// Copyright (c) 2012, 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.
+
+library pub.progress;
+
+import 'dart:async';
+import 'dart:io';
+
+import 'log.dart' as log;
+
+/// A live-updating progress indicator for long-running log entries.
+class Progress {
+  /// The timer used to write "..." during a progress log.
+  Timer _timer;
+
+  /// The [Stopwatch] used to track how long a progress log has been running.
+  final _stopwatch = new Stopwatch();
+
+  /// The progress message as it's being incrementally appended. When the
+  /// progress is done, a single entry will be added to the log for it.
+  final String _message;
+
+  Progress(this._message) {
+    _stopwatch.start();
+
+    if (log.json.enabled) return;
+
+    // Only animate if we're writing to a TTY in human format.
+    if (stdioType(stdout) == StdioType.TERMINAL) {
+      _update();
+      _timer = new Timer.periodic(new Duration(milliseconds: 100), (_) {
+        _update();
+      });
+    } else {
+      stdout.write("$_message... ");
+    }
+  }
+
+  /// Stops the progress indicator.
+  ///
+  /// Returns the complete final progress message.
+  String stop() {
+    _stopwatch.stop();
+
+    // If we aren't animating, just log the final time.
+    if (log.json.enabled) {
+      // Do nothing.
+    } else if (_timer == null) {
+      stdout.writeln(_time);
+    } else {
+      _timer.cancel();
+
+      // Show one final update.
+      _update();
+      stdout.writeln();
+    }
+
+    return "$_message... ${_time}";
+  }
+
+  /// Gets the current progress time as a parenthesized, formatted string.
+  String get _time {
+    var elapsed = _stopwatch.elapsed;
+    var time = "(";
+
+    // TODO(rnystrom): Move this somewhere reusable.
+    if (elapsed.inMinutes > 0) {
+      time += "${elapsed.inMinutes}:";
+    }
+
+    var s = elapsed.inSeconds % 59;
+    var ms = (elapsed.inMilliseconds % 1000) ~/ 100;
+    return time + "$s.${ms}s)";
+  }
+
+  /// Refreshes the progress line.
+  void _update() {
+    stdout.write("\r$_message... ");
+
+    // Show the time only once it gets noticeably long.
+    if (_stopwatch.elapsed.inSeconds > 0) {
+      stdout.write(log.gray(_time));
+    }
+  }
+}