Support empty list insertion for attributes

lib/PhpParser/PrettyPrinterAbstract.php

@@ -920,7 +920,7 @@ abstract class PrettyPrinterAbstract {
                 $result .= $this->p($delayedAddNode, true);
                 $first = false;
             }
-            $result .= $extraRight;
+            $result .= $extraRight === "\n" ? $this->nl : $extraRight;
         }
 
         return $result;
@@ -1448,6 +1448,16 @@ abstract class PrettyPrinterAbstract {
             'Stmt_ClassMethod->params' => ['(', '', ''],
             'Stmt_Interface->extends' => [null, ' extends ', ''],
             'Stmt_Function->params' => ['(', '', ''],
+            'Stmt_Interface->attrGroups' => [null, '', "\n"],
+            'Stmt_Class->attrGroups' => [null, '', "\n"],
+            'Stmt_ClassConst->attrGroups' => [null, '', "\n"],
+            'Stmt_ClassMethod->attrGroups' => [null, '', "\n"],
+            'Stmt_Function->attrGroups' => [null, '', "\n"],
+            'Stmt_Property->attrGroups' => [null, '', "\n"],
+            'Stmt_Trait->attrGroups' => [null, '', "\n"],
+            'Expr_ArrowFunction->attrGroups' => [null, '', ' '],
+            'Expr_Closure->attrGroups' => [null, '', ' '],
+            'Expr_PrintableNewAnonClass->attrGroups' => [\T_NEW, ' ', ''],
 
             /* These cannot be empty to start with:
              * Expr_Isset->vars

test/code/formatPreservation/attributes.test

@@ -102,7 +102,6 @@ function() {};
 fn()
     => 42;
 -----
-// TODO: Currently we lose formatting for this case.
 $attrGroup = new Node\AttributeGroup([
     new Node\Attribute(new Node\Name('A'), []),
 ]);
@@ -119,39 +118,32 @@ $stmts[6]->expr->attrGroups[] = $attrGroup;
 -----
 <?php
 #[A]
-class X
-{
+class X {
     #[A]
-    public function m()
-    {
-    }
+    public function m() {}
+
     #[A]
-    public $prop;
+    public
+        $prop;
+
     #[A]
-    const X = 42;
+    const
+        X = 42;
 }
 
 #[A]
-trait X
-{
-}
+trait X {}
 
 #[A]
-interface X
-{
-}
+interface X {}
 
 #[A]
-function f()
-{
-}
+function f() {}
 
-new #[A] class
-{
-};
-#[A] function () {
-};
-#[A] fn() => 42;
+new #[A] class {};
+#[A] function() {};
+#[A] fn()
+    => 42;
 -----
 <?php
 
@@ -176,4 +168,4 @@ class X {};
     B,
     C,
 ]
-class X {};
+class X {};

test/code/formatPreservation/emptyListInsertion.test

@@ -107,4 +107,4 @@ Foo
 
 new class
 ($a, $b)
-extends Foo {};
+extends Foo {};