Insert a blank line before and after classes.

lib/src/source_visitor.dart

 // Copyright (c) 2014, 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 dart_style.src.source_visitor;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 
@@ skipping 417 matching lines @@
     // Put a blank line between the library tag and the other directives.
     var directives = node.directives;
     if (directives.isNotEmpty && directives.first is LibraryDirective) {
       visit(directives.first);
       twoNewlines();
 
       directives = directives.skip(1);
     }
 
     visitNodes(directives, between: oneOrTwoNewlines);
-    visitNodes(node.declarations,
-        before: twoNewlines, between: oneOrTwoNewlines);
+
+    if (node.declarations.isNotEmpty) {
+      twoNewlines();
+
+      for (var i = 0; i < node.declarations.length; i++) {
+        visit(node.declarations[i]);
+
+        if (i < node.declarations.length - 1) {
+          // Require blank lines around classes.
+          if (node.declarations[i] is ClassDeclaration ||
+              node.declarations[i + 1] is ClassDeclaration) {
+            twoNewlines();
+          } else {
+            // Functions and variables can be more tightly packed.
+            oneOrTwoNewlines();
+          }
+        }
+      }
+    }
   }
 
   visitConditionalExpression(ConditionalExpression node) {
     builder.nestExpression();
     visit(node.condition);
 
     builder.startSpan();
 
     // If we split after one clause in a conditional, always split after both.
     builder.startRule();
@@ skipping 1598 matching lines @@
   /// Gets the 1-based line number that the beginning of [token] lies on.
   int _startLine(Token token) => _lineInfo.getLocation(token.offset).lineNumber;
 
   /// Gets the 1-based line number that the end of [token] lies on.
   int _endLine(Token token) => _lineInfo.getLocation(token.end).lineNumber;
 
   /// Gets the 1-based column number that the beginning of [token] lies on.
   int _startColumn(Token token) =>
       _lineInfo.getLocation(token.offset).columnNumber;
 }