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

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

 // Copyright (c) 2012, 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.
 
 part of js_ast;
 
 
 class JavaScriptPrintingOptions {
   final bool shouldCompressOutput;
   final bool minifyLocalVariables;
@@ skipping 186 matching lines @@
   }
 
   visitAll(List<Node> nodes) {
     nodes.forEach(visit);
   }
 
   visitProgram(Program program) {
     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) {
       // If [shouldCompressOutput] is false, then the 'lineOut' will insert
       // the separation.
       out(" ");
     } else {
       lineOut();
     }
     indentMore();
     visit(body);
     indentLess();
     return false;
   }
 
   void blockOutWithoutBraces(Node node) {
     if (node is Block) {
       context.enterNode(node);
       Block block = node;
       block.statements.forEach(blockOutWithoutBraces);
       context.exitNode(node);
     } else {
       visit(node);
     }
   }
 
-  void blockOut(Block node, bool shouldIndent, bool needsNewline) {
+  void blockOut(Block node, {bool shouldIndent, bool needsNewline}) {
     if (shouldIndent) indent();
     context.enterNode(node);
     out("{");
     lineOut();
     indentMore();
     node.statements.forEach(blockOutWithoutBraces);
     indentLess();
     indent();
     out("}");
     context.exitNode(node);
     if (needsNewline) lineOut();
   }
 
   visitBlock(Block block) {
-    blockOut(block, true, true);
+    blockOut(block, shouldIndent: true, needsNewline: true);
   }
 
   visitExpressionStatement(ExpressionStatement expressionStatement) {
     indent();
     visitNestedExpression(expressionStatement.expression, EXPRESSION,
                           newInForInit: false, newAtStatementBegin: true);
     outSemicolonLn();
   }
 
   visitEmptyStatement(EmptyStatement nop) {
     outIndentLn(";");
   }
 
   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();
     out("(");
     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();
       } else {
         indent();
       }
       out("else");
       if (elsePart is If) {
         pendingSpace = true;
         ifOut(elsePart, false);
@@ skipping 117 matching lines @@
   visitThrow(Throw node) {
     outIndent("throw");
     pendingSpace = true;
     visitNestedExpression(node.expression, EXPRESSION,
                           newInForInit: false, newAtStatementBegin: false);
     outSemicolonLn();
   }
 
   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();
     }
   }
 
   visitCatch(Catch node) {
     spaceOut();
     out("catch");
     spaceOut();
     out("(");
     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) {
     outIndent("switch");
     spaceOut();
     out("(");
     visitNestedExpression(node.key, EXPRESSION,
                           newInForInit: false, newAtStatementBegin: false);
     out(")");
     spaceOut();
@@ skipping 52 matching lines @@
       case const AsyncModifier.async():
         out(' async');
         break;
       case const AsyncModifier.syncStar():
         out(' sync*');
         break;
       case const AsyncModifier.asyncStar():
         out(' async*');
         break;
     }
-    blockBody(fun.body, needsSeparation: false, needsNewline: false);
+    spaceOut();
+    blockOut(fun.body, shouldIndent: false, needsNewline: false);
     localNamer.leaveScope();
   }
 
   visitFunctionDeclaration(FunctionDeclaration declaration) {
     VarCollector vars = new VarCollector();
     vars.visitFunctionDeclaration(declaration);
     indent();
     functionOut(declaration.function, declaration.name, vars);
     lineOut();
   }
@@ skipping 711 matching lines @@
         codes.add(nthLetter((n ~/ nameSpaceSize) % LETTERS));
       }
       codes.add(charCodes.$0 + digit);
       newName = new String.fromCharCodes(codes);
     }
     assert(new RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
     maps.last[oldName] = newName;
     return newName;
   }
 }