bug #2995 Fix partial output leak when a PHP fatal error occurs (fabpot)

This PR was merged into the 1.x branch.

Discussion
----------

Fix partial output leak when a PHP fatal error occurs

closes #1962 (thank you @fluff for the "trick")

Commits
-------

6196fe5 fixed partial output leak when a PHP fatal error occurs

Author: fabpot

CHANGELOG

@@ -1,5 +1,6 @@
 * 1.41.0 (2019-XX-XX)
 
+ * fixed partial output leak when a PHP fatal error occurs
  * optimized context access on PHP 7.4
 
 * 1.40.1 (2019-04-29)

src/Extension/DebugExtension.php

@@ -54,7 +54,7 @@ function twig_var_dump(Environment $env, $context, array $vars = [])
         return;
     }
 
-    ob_start();
+    ob_start(function () { return ''; });
 
     if (!$vars) {
         $vars = [];

src/Node/MacroNode.php

@@ -104,7 +104,7 @@ public function compile(Compiler $compiler)
             ->outdent()
             ->write("]);\n\n")
             ->write("\$blocks = [];\n\n")
-            ->write("ob_start();\n")
+            ->write("ob_start(function () { return ''; });\n")
             ->write("try {\n")
             ->indent()
             ->subcompile($this->getNode('body'))

src/Node/SetNode.php

@@ -58,7 +58,7 @@ public function compile(Compiler $compiler)
         } else {
             if ($this->getAttribute('capture')) {
                 $compiler
-                    ->write("ob_start();\n")
+                    ->write("ob_start(function () { return ''; });\n")
                     ->subcompile($this->getNode('values'))
                 ;
             }

src/Node/SpacelessNode.php

@@ -31,7 +31,7 @@ public function compile(Compiler $compiler)
     {
         $compiler
             ->addDebugInfo($this)
-            ->write("ob_start();\n")
+            ->write("ob_start(function () { return ''; });\n")
             ->subcompile($this->getNode('body'))
             ->write("echo trim(preg_replace('/>\s+</', '><', ob_get_clean()));\n")
         ;

src/Template.php

@@ -253,7 +253,7 @@ public function displayBlock($name, array $context, array $blocks = [], $useBloc
      */
     public function renderParentBlock($name, array $context, array $blocks = [])
     {
-        ob_start();
+        ob_start(function () { return ''; });
         $this->displayParentBlock($name, $context, $blocks);
 
         return ob_get_clean();
@@ -274,7 +274,7 @@ public function renderParentBlock($name, array $context, array $blocks = [])
      */
     public function renderBlock($name, array $context, array $blocks = [], $useBlocks = true)
     {
-        ob_start();
+        ob_start(function () { return ''; });
         $this->displayBlock($name, $context, $blocks, $useBlocks);
 
         return ob_get_clean();
@@ -417,7 +417,7 @@ public function display(array $context, array $blocks = [])
     public function render(array $context)
     {
         $level = ob_get_level();
-        ob_start();
+        ob_start(function () { return ''; });
         try {
             $this->display($context);
         } catch (\Exception $e) {

src/TemplateWrapper.php

@@ -96,7 +96,7 @@ public function renderBlock($name, $context = [])
     {
         $context = $this->env->mergeGlobals($context);
         $level = ob_get_level();
-        ob_start();
+        ob_start(function () { return ''; });
         try {
             $this->template->displayBlock($name, $context);
         } catch (\Exception $e) {

test/Twig/Tests/Node/MacroTest.php

@@ -59,7 +59,7 @@ public function getfoo(\$__foo__ = null, \$__bar__ = "Foo"$declaration)
 
     \$blocks = [];
 
-    ob_start();
+    ob_start(function () { return ''; });
     try {
         echo "foo";
     } catch (\Exception \$e) {

test/Twig/Tests/Node/SetTest.php

@@ -49,7 +49,7 @@ public function getTests()
         $node = new SetNode(true, $names, $values, 1);
         $tests[] = [$node, <<<EOF
 // line 1
-ob_start();
+ob_start(function () { return ''; });
 echo "foo";
 \$context["foo"] = ('' === \$tmp = ob_get_clean()) ? '' : new Markup(\$tmp, \$this->env->getCharset());
 EOF

test/Twig/Tests/Node/SpacelessTest.php

@@ -32,7 +32,7 @@ public function getTests()
         return [
             [$node, <<<EOF
 // line 1
-ob_start();
+ob_start(function () { return ''; });
 echo "<div>   <div>   foo   </div>   </div>";
 echo trim(preg_replace('/>\s+</', '><', ob_get_clean()));
 EOF