Avoid printing braces for one-statement blocks in js-printer.

pkg/compiler/lib/src/js/printer.dart

Index: pkg/compiler/lib/src/js/printer.dart
diff --git a/pkg/compiler/lib/src/js/printer.dart b/pkg/compiler/lib/src/js/printer.dart
index b1acebaa8f82e18b0159660b79714a7ba7637f7c..71ee7b75e2f61768da176b95b298a6c36b17e802 100644
--- a/pkg/compiler/lib/src/js/printer.dart
+++ b/pkg/compiler/lib/src/js/printer.dart
@@ -204,10 +204,14 @@ class Printer implements NodeVisitor {
     visitAll(program.body);
   }
 
-  bool blockBody(Node body, {bool needsSeparation, bool needsNewline}) {
+  bool blockBody(Statement body, {bool needsSeparation, bool needsNewline}) {
+    if (body is Block && body.statements.length == 1) {
+      Block block = body;
+      body = block.statements.single;
+    }
     if (body is Block) {
       spaceOut();
-      blockOut(body, false, needsNewline);
+      blockOut(body, shouldIndent: false, needsNewline: needsNewline);
       return true;
     }
     if (shouldCompressOutput && needsSeparation) {
@@ -234,7 +238,7 @@ class Printer implements NodeVisitor {
     }
   }
 
-  void blockOut(Block node, bool shouldIndent, bool needsNewline) {
+  void blockOut(Block node, {bool shouldIndent, bool needsNewline}) {
     if (shouldIndent) indent();
     context.enterNode(node);
     out("{");
@@ -249,7 +253,7 @@ class Printer implements NodeVisitor {
   }
 
   visitBlock(Block block) {
-    blockOut(block, true, true);
+    blockOut(block, shouldIndent: true, needsNewline: true);
   }
 
   visitExpressionStatement(ExpressionStatement expressionStatement) {
@@ -264,19 +268,17 @@ class Printer implements NodeVisitor {
   }
 
   void ifOut(If node, bool shouldIndent) {
-    Node then = node.then;
-    Node elsePart = node.otherwise;
+    Statement then = node.then;
+    Statement elsePart = node.otherwise;
     bool hasElse = node.hasElse;
 
     // Handle dangling elses and a work-around for Android 4.0 stock browser.
     // Android 4.0 requires braces for a single do-while in the `then` branch.
     // See issue 10923.
-    if (hasElse) {
-      bool needsBraces = node.then.accept(danglingElseVisitor) || then is Do;
-      if (needsBraces) {
-        then = new Block(<Statement>[then]);
-      }
-    }
+    bool needsBracesInThen = hasElse

[floitsch, 2015/02/23 13:46:08]

bool needsBracesInThen =
    hasElse && (then.accept(danglingElseVisitor) || then is Do);

[sigurdm, 2015/02/23 14:13:22]

Acknowledged.
This change has been undone.

+        ? node.then.accept(danglingElseVisitor) || then is Do
+        : false;
+
     if (shouldIndent) indent();
     out("if");
     spaceOut();
@@ -284,8 +286,15 @@ class Printer implements NodeVisitor {
     visitNestedExpression(node.condition, EXPRESSION,
                           newInForInit: false, newAtStatementBegin: false);
     out(")");
-    bool thenWasBlock =
-        blockBody(then, needsSeparation: false, needsNewline: !hasElse);
+    bool thenWasBlock;
+    if (needsBracesInThen) {
+      spaceOut();
+      blockOut(new Block([then]), shouldIndent: false, needsNewline: !hasElse);
+      thenWasBlock = true;
+    } else {

[floitsch, 2015/02/23 13:46:08]

This probably broke the dangling-else:

if (x) {
  if (y) print('foo');
} else print('bar');

The danglingElseVisitor says that 'node.then' is a block and therefore doesn't
need braces.

However, the 'blockBody' will now remove it.

[sigurdm, 2015/02/23 14:13:22]

Yes, I just realized that. I will remove the blocks as a pass before.

+      thenWasBlock =
+          blockBody(then, needsSeparation: false, needsNewline: !hasElse);
+    }
     if (hasElse) {
       if (thenWasBlock) {
         spaceOut();
@@ -423,14 +432,16 @@ class Printer implements NodeVisitor {
 
   visitTry(Try node) {
     outIndent("try");
-    blockBody(node.body, needsSeparation: true, needsNewline: false);
+    spaceOut();
+    blockOut(node.body, shouldIndent: false, needsNewline: false);
     if (node.catchPart != null) {
       visit(node.catchPart);
     }
     if (node.finallyPart != null) {
       spaceOut();
       out("finally");
-      blockBody(node.finallyPart, needsSeparation: true, needsNewline: true);
+      spaceOut();
+      blockOut(node.finallyPart, shouldIndent: false, needsNewline: true);
     } else {
       lineOut();
     }
@@ -444,7 +455,8 @@ class Printer implements NodeVisitor {
     visitNestedExpression(node.declaration, EXPRESSION,
                           newInForInit: false, newAtStatementBegin: false);
     out(")");
-    blockBody(node.body, needsSeparation: false, needsNewline: true);
+    spaceOut();
+    blockOut(node.body, shouldIndent: false, needsNewline: false);
   }
 
   visitSwitch(Switch node) {
@@ -517,7 +529,8 @@ class Printer implements NodeVisitor {
         out(' async*');
         break;
     }
-    blockBody(fun.body, needsSeparation: false, needsNewline: false);
+    spaceOut();
+    blockOut(fun.body, shouldIndent: false, needsNewline: false);
     localNamer.leaveScope();
   }