added a way to catch undefined filters (like functions)

lib/Twig/Environment.php

@@ -647,27 +647,46 @@ class Twig_Environment
     public function addFilter($name, Twig_FilterInterface $filter)
     {
         if (null === $this->filters) {
-            $this->getFilters();
+            $this->loadFilters();
         }
 
         $this->filters[$name] = $filter;
     }
 
+    /**
+     * Get a filter by name.
+     *
+     * Subclasses may override this method and load filters differently;
+     * so no list of filters is available.
+     *
+     * @param string $name The filter name
+     *
+     * @return Twig_Filter|false A Twig_Filter instance or false if the filter does not exists
+     */
+    public function getFilter($name)
+    {
+        if (null === $this->filters) {
+            $this->loadFilters();
+        }
+
+        if (isset($this->filters[$name])) {
+            return $this->filters[$name];
+        }
+
+        return false;
+    }
+
     /**
      * Gets the registered Filters.
      *
      * @return Twig_FilterInterface[] An array of Twig_FilterInterface instances
      */
-    public function getFilters()
+    protected function loadFilters()
     {
-        if (null === $this->filters) {
-            $this->filters = array();
-            foreach ($this->getExtensions() as $extension) {
-                $this->filters = array_merge($this->filters, $extension->getFilters());
-            }
+        $this->filters = array();
+        foreach ($this->getExtensions() as $extension) {
+            $this->filters = array_merge($this->filters, $extension->getFilters());
         }
-
-        return $this->filters;
     }
 
     /**
@@ -720,12 +739,12 @@ class Twig_Environment
     /**
      * Get a function by name.
      *
-     * Subclasses may override getFunction($name) and load functions differently;
+     * Subclasses may override this method and load functions differently;
      * so no list of functions is available.
      *
      * @param string $name function name
      *
-     * @return Twig_Function|null A Twig_Function instance or null if the function does not exists
+     * @return Twig_Function|false A Twig_Function instance or false if the function does not exists
      */
     public function getFunction($name)
     {
@@ -737,7 +756,7 @@ class Twig_Environment
             return $this->functions[$name];
         }
 
-        return null;
+        return false;
     }
 
     protected function loadFunctions() {

lib/Twig/Node/Expression/Filter.php

@@ -18,12 +18,10 @@ class Twig_Node_Expression_Filter extends Twig_Node_Expression
 
     public function compile(Twig_Compiler $compiler)
     {
-        $filterMap = $compiler->getEnvironment()->getFilters();
         $name = $this->getNode('filter')->getAttribute('value');
-        if (!isset($filterMap[$name])) {
+        if (false === $filter = $compiler->getEnvironment()->getFilter($name)) {
             throw new Twig_Error_Syntax(sprintf('The filter "%s" does not exist', $name), $this->getLine());
         }
-        $filter = $filterMap[$name];
 
         // The default filter is intercepted when the filtered value
         // is a name (like obj) or an attribute (like obj.attr)

lib/Twig/Node/Expression/Function.php

@@ -18,7 +18,7 @@ class Twig_Node_Expression_Function extends Twig_Node_Expression
     public function compile(Twig_Compiler $compiler)
     {
         $function = $compiler->getEnvironment()->getFunction($this->getNode('name')->getAttribute('name'));
-        if (!$function) {
+        if (false === $function) {
             throw new Twig_Error_Syntax(sprintf('The function "%s" does not exist', $this->getNode('name')->getAttribute('name')), $this->getLine());
         }
 

lib/Twig/NodeVisitor/Escaper.php

@@ -94,11 +94,10 @@ class Twig_NodeVisitor_Escaper implements Twig_NodeVisitorInterface
 
     protected function preEscapeFilterNode(Twig_Node_Expression_Filter $filter, Twig_Environment $env)
     {
-        $filterMap = $env->getFilters();
         $name = $filter->getNode('filter')->getAttribute('value');
 
-        if (isset($filterMap[$name])) {
-            $type = $filterMap[$name]->getPreEscape();
+        if (false !== $f = $env->getFilter($name)) {
+            $type = $f->getPreEscape();
             if (null === $type) {
                 return $filter;
             }

lib/Twig/NodeVisitor/SafeAnalysis.php

@@ -50,11 +50,10 @@ class Twig_NodeVisitor_SafeAnalysis implements Twig_NodeVisitorInterface
             $this->setSafe($node, $safe);
         } elseif ($node instanceof Twig_Node_Expression_Filter) {
             // filter expression is safe when the filter is safe
-            $filterMap = $env->getFilters();
             $name = $node->getNode('filter')->getAttribute('value');
             $args = $node->getNode('arguments');
-            if (isset($filterMap[$name])) {
-                $this->setSafe($node, $filterMap[$name]->getSafe($args));
+            if (false !== $filter = $env->getFilter($name)) {
+                $this->setSafe($node, $filter->getSafe($args));
             } else {
                 $this->setSafe($node, array());
             }
@@ -63,7 +62,7 @@ class Twig_NodeVisitor_SafeAnalysis implements Twig_NodeVisitorInterface
             $name = $node->getNode('name')->getAttribute('name');
             $args = $node->getNode('arguments');
             $function = $env->getFunction($name);
-            if (null !== $function) {
+            if (false !== $function) {
                 $this->setSafe($node, $function->getSafe($args));
             } else {
                 $this->setSafe($node, array());