dartfmt gets opinionated about 'gratuitous' linebreaks.

pkg/analyzer/lib/src/services/formatter_impl.dart

Index: pkg/analyzer/lib/src/services/formatter_impl.dart
===================================================================
--- pkg/analyzer/lib/src/services/formatter_impl.dart	(revision 31210)
+++ pkg/analyzer/lib/src/services/formatter_impl.dart	(working copy)
@@ -352,6 +352,10 @@
   /// A flag to indicate that a newline should be emitted before the next token.
   bool needsNewline = false;
 
+  /// A flag to indicate that user introduced newlines should be emitted before
+  /// the next token.
+  bool preserveNewlines = false;
+
   /// A counter for spaces that should be emitted preceding the next token.
   int leadingSpaces = 0;
 
@@ -462,7 +466,8 @@
   visitCascadeExpression(CascadeExpression node) {
     visit(node.target);
     indent(2);
-    visitNodes(node.cascadeSections);
+    newlines();
+    visitNodes(node.cascadeSections, separatedBy: newlines);
     unindent(2);
   }
 
@@ -490,6 +495,7 @@
   }
 
   visitClassDeclaration(ClassDeclaration node) {
+    preserveLeadingNewlines();
     modifier(node.abstractKeyword);
     token(node.classKeyword);
     space();
@@ -547,6 +553,8 @@
 
     visitNodes(node.declarations, separatedBy: newlines);
 
+    preserveLeadingNewlines();
+
     // Handle trailing whitespace
     token(node.endToken /* EOF */);
 
@@ -801,6 +809,7 @@
   }
 
   visitFunctionDeclaration(FunctionDeclaration node) {
+    preserveLeadingNewlines();
     visitNode(node.returnType, followedBy: space);
     token(node.propertyKeyword, followedBy: space);
     visit(node.name);
@@ -965,10 +974,12 @@
     modifier(node.constKeyword);
     visitNode(node.typeArguments, followedBy: space);
     token(node.leftBracket);
+    newlines();
     indent();
-    visitCommaSeparatedNodes(node.entries);
+    visitCommaSeparatedNodes(node.entries, followedBy: newlines);
     optionalTrailingComma(node.rightBracket);
     unindent();
+    newlines();
     token(node.rightBracket);
   }
 
@@ -1309,7 +1320,11 @@
   }
 
   /// Visit a comma-separated list of [nodes] if not null.
-  visitCommaSeparatedNodes(NodeList<ASTNode> nodes) {
+  visitCommaSeparatedNodes(NodeList<ASTNode> nodes, {followedBy(): null}) {
+    //TODO(pquitslund): handle this more neatly

[pquitslund, 2013/12/18 17:16:47]

EG: by introducing a const pointer to the space function.

[Brian Wilkerson, 2013/12/18 17:53:07]

In order to do that, the space function will have to be a static function. But
if it's a static function, then it's already a constant, so you don't need an
additional const variable to point to it and should be able to write
"{followedBy(): space}".

+    if (followedBy == null) {
+      followedBy = space;
+    }
     if (nodes != null) {
       var size = nodes.length;
       if (size > 0) {
@@ -1319,7 +1334,7 @@
           if (i > 0) {
             var comma = node.beginToken.previous;
             token(comma);
-            space();
+            followedBy();
           }
           node.accept(this);
         }
@@ -1368,6 +1383,12 @@
     }
   }
 
+  /// Indicate that user introduced newlines should be emitted before the next
+  /// token.
+  preserveLeadingNewlines() {
+    preserveNewlines = true;
+  }
+
   token(Token token, {precededBy(), followedBy(), int minNewlines: 0}) {
     if (token != null) {
       if (needsNewline) {
@@ -1478,7 +1499,11 @@
       currentToken = comment != null ? comment : token;
     }
 
-    var lines = max(min, countNewlinesBetween(previousToken, currentToken));
+    var lines = 0;
+    if (needsNewline || preserveNewlines) {
+      lines = max(min, countNewlinesBetween(previousToken, currentToken));
+      preserveNewlines = false;
+    }
     emitNewlines(lines);
 
     previousToken =