Add lints from package:pedantic (flutter#66)

- Fix a control_flow_in_finally by removing the nested try/catch which
  was set up for ordering of behavior and instead check for a closed
  controller in both places.
- Fix a prefer_is_not_empty.

Author: natebosch

analysis_options.yaml

@@ -1,3 +1,4 @@
+include: package:pedantic/analysis_options.yaml
 analyzer:
   strong-mode:
     implicit-casts: false

lib/src/file_watcher/polling.dart

@@ -60,16 +60,14 @@ class _PollingFileWatcher implements FileWatcher, ManuallyClosedWatcher {
 
     DateTime modified;
     try {
-      try {
-        modified = await getModificationTime(path);
-      } finally {
-        if (_eventsController.isClosed) return;
-      }
+      modified = await getModificationTime(path);
     } on FileSystemException catch (error, stackTrace) {
-      _eventsController.addError(error, stackTrace);
-      close();
-      return;
+      if (!_eventsController.isClosed) {
+        _eventsController.addError(error, stackTrace);
+        await close();
+      }
     }
+    if (_eventsController.isClosed) return;
 
     if (_lastModified == modified) return;
 
@@ -84,8 +82,8 @@ class _PollingFileWatcher implements FileWatcher, ManuallyClosedWatcher {
     }
   }
 
-  void close() {
+  Future<void> close() async {
     _timer.cancel();
-    _eventsController.close();
+    await _eventsController.close();
   }
 }

lib/src/path_set.dart

@@ -136,7 +136,7 @@ class PathSet {
       if (entry == null) return false;
     }
 
-    return !entry.contents.isEmpty;
+    return entry.contents.isNotEmpty;
   }
 
   /// All of the paths explicitly added to this set.

pubspec.yaml

@@ -16,5 +16,6 @@ dependencies:
 
 dev_dependencies:
   benchmark_harness: ^1.0.4
+  pedantic: ^1.1.0
   test: '>=0.12.42 <2.0.0'
   test_descriptor: ^1.0.0