Merge pull request #2758 from devoncarew/listen_update

update listen to work w/ ios devices

packages/flutter_tools/lib/src/commands/listen.dart

@@ -5,17 +5,19 @@
 import 'dart:async';
 import 'dart:io';
 
+import '../base/os.dart';
 import '../base/process.dart';
 import '../globals.dart';
 import 'run.dart';
 
 class ListenCommand extends RunCommandBase {
+  ListenCommand({ this.singleRun: false });
+
   @override
   final String name = 'listen';
 
   @override
-  final String description =
+  final String description = 'Listen for changes to files and reload the running app.';
-    'Listen for changes to files and reload the running app (Android only).';
 
   @override
   final String usageFooter =
@@ -25,11 +27,6 @@ class ListenCommand extends RunCommandBase {
   /// Only run once. Used for testing.
   final bool singleRun;
 
-  ListenCommand({ this.singleRun: false });
-
-  @override
-  bool get androidOnly => true;
-
   @override
   bool get requiresDevice => true;
 
@@ -38,16 +35,30 @@ class ListenCommand extends RunCommandBase {
     await downloadApplicationPackages();
     await downloadToolchain();
 
-    List<String> watchCommand = _constructWatchCommand(() sync* {
+    Iterable<String> directories = () sync* {
       yield* argResults.rest;
       yield '.';
       yield 'lib';
-    }());
+    }();
+
+    List<String> watchCommand = _constructWatchCommand(directories);
+
+    if (watchCommand == null)
+      return 1;
+
+    printStatus('Listening for changes in '
+      '${directories.map((String name) => "'$name${Platform.pathSeparator}'").join(', ')}'
+      '.');
 
     int result = 0;
     bool firstTime = true;
     do {
-      printStatus('Updating running Flutter apps...');
+      printStatus('');
+
+      // TODO(devoncarew): We could print out here what changes we detected that caused a re-run.
+      if (!firstTime)
+        printStatus('Re-running app...');
+
       result = await startApp(
         deviceForCommand,
         applicationPackages,
@@ -62,29 +73,26 @@ class ListenCommand extends RunCommandBase {
       );
       firstTime = false;
     } while (!singleRun && result == 0 && _watchDirectory(watchCommand));
+
     return 0;
   }
 
   List<String> _constructWatchCommand(Iterable<String> directories) {
     if (Platform.isMacOS) {
-      try {
+      if (os.which('fswatch') == null) {
-        runCheckedSync(<String>['which', 'fswatch']);
-      } catch (e) {
         printError('"listen" command is only useful if you have installed '
-            'fswatch on Mac.  Run "brew install fswatch" to install it with '
+          'fswatch on Mac. Run "brew install fswatch" to install it with homebrew.');
-            'homebrew.');
         return null;
-      }
+      } else {
         return <String>['fswatch', '-r', '-v', '-1']..addAll(directories);
+      }
     } else if (Platform.isLinux) {
-      try {
+      if (os.which('inotifywait') == null) {
-        runCheckedSync(<String>['which', 'inotifywait']);
-      } catch (e) {
         printError('"listen" command is only useful if you have installed '
           'inotifywait on Linux. Run "apt-get install inotify-tools" or '
           'equivalent to install it.');
         return null;
-      }
+      } else {
         return <String>[
           'inotifywait',
           '-r',
@@ -93,14 +101,15 @@ class ListenCommand extends RunCommandBase {
           // from the editor watching files.
           'modify,close_write,move,create,delete',
         ]..addAll(directories);
+      }
     } else {
       printError('"listen" command is only available on Mac and Linux.');
     }
+
     return null;
   }
 
   bool _watchDirectory(List<String> watchCommand) {
-    printStatus('Attempting to listen to these directories: ${watchCommand.join(", ")}');
     assert(watchCommand != null);
     try {
       runCheckedSync(watchCommand);