minor #2618 Optimized compilation for arrays when using a['b'] notation (fabpot)

This PR was squashed before being merged into the 2.x branch (closes #2618).

Discussion
----------

Optimized compilation for arrays when using a['b'] notation

Under certain conditions, and thanks to the `??` operator, it's possible to optimize array calls (and avoid the call to `twig_get_attribute()`).

On my local machine, code is almost twice as fast, which is nice if you are using a lot of `a["b"]` calls of nested ones.

refs #2547

Commits
-------

6f7ea45c optimized nested array calls
f3b8f4a8 added some tests
d501e0e5 optimized compilation for arrays when using a['b'] notation under certain conditions

lib/Twig/Node/Expression/GetAttr.php

@@ -23,6 +23,30 @@ class Twig_Node_Expression_GetAttr extends Twig_Node_Expression
 
     public function compile(Twig_Compiler $compiler)
     {
+        // optimize array calls
+        if (
+            (!$compiler->getEnvironment()->isStrictVariables() || $this->getAttribute('ignore_strict_check'))
+            && !$this->getAttribute('is_defined_test')
+            && Twig_Template::ARRAY_CALL === $this->getAttribute('type')
+        ) {
+            $var = '$'.$compiler->getVarName();
+            $compiler
+                ->raw('(('.$var.' = ')
+                ->subcompile($this->getNode('node'))
+                ->raw(') && is_array(')
+                ->raw($var)
+                ->raw(') || ')
+                ->raw($var)
+                ->raw(' instanceof ArrayAccess ? (')
+                ->raw($var)
+                ->raw('[')
+                ->subcompile($this->getNode('attribute'))
+                ->raw('] ?? null) : null)')
+            ;
+
+            return;
+        }
+
         $compiler->raw('twig_get_attribute($this->env, $this->source, ');
 
         if ($this->getAttribute('ignore_strict_check')) {

test/Twig/Tests/Fixtures/expressions/array.test

@@ -37,8 +37,11 @@ Twig supports array notation
 {% set ary = { (a): 'a', (b): 'b', 'c': 'c', (a ~ b): 'd' } %}
 {{ ary|keys|join(',') }}
 {{ ary|join(',') }}
+
+{# ArrayAccess #}
+{{ array_access['a'] }}
 --DATA--
-return array('bar' => 'bar', 'foo' => array('bar' => 'bar'))
+return array('bar' => 'bar', 'foo' => array('bar' => 'bar'), 'array_access' => new ArrayObject(array('a' =>  'b')))
 --EXPECT--
 1,2
 foo,bar
@@ -59,3 +62,5 @@ FOO,BAR,
 
 1,foo,c,1foo
 a,b,c,d
+
+b

test/Twig/Tests/Fixtures/expressions/array_non_strict.test

@@ -0,0 +1,68 @@
+--TEST--
+Twig supports array notation
+--TEMPLATE--
+{# empty array #}
+{{ []|join(',') }}
+
+{{ [1, 2]|join(',') }}
+{{ ['foo', "bar"]|join(',') }}
+{{ {0: 1, 'foo': 'bar'}|join(',') }}
+{{ {0: 1, 'foo': 'bar'}|keys|join(',') }}
+
+{{ {0: 1, foo: 'bar'}|join(',') }}
+{{ {0: 1, foo: 'bar'}|keys|join(',') }}
+
+{# nested arrays #}
+{% set a = [1, 2, [1, 2], {'foo': {'foo': 'bar'}}] %}
+{{ a[2]|join(',') }}
+{{ a[3]["foo"]|join(',') }}
+
+{# works even if [] is used inside the array #}
+{{ [foo[bar]]|join(',') }}
+
+{# elements can be any expression #}
+{{ ['foo'|upper, bar|upper, bar == foo]|join(',') }}
+
+{# arrays can have a trailing , like in PHP #}
+{{
+  [
+    1,
+    2,
+  ]|join(',')
+}}
+
+{# keys can be any expression #}
+{% set a = 1 %}
+{% set b = "foo" %}
+{% set ary = { (a): 'a', (b): 'b', 'c': 'c', (a ~ b): 'd' } %}
+{{ ary|keys|join(',') }}
+{{ ary|join(',') }}
+
+{# ArrayAccess #}
+{{ array_access['a'] }}
+--DATA--
+return array('bar' => 'bar', 'foo' => array('bar' => 'bar'), 'array_access' => new ArrayObject(array('a' =>  'b')))
+--CONFIG--
+return array('strict_variables' => false)
+--EXPECT--
+1,2
+foo,bar
+1,bar
+0,foo
+
+1,bar
+0,foo
+
+1,2
+bar
+
+bar
+
+FOO,BAR,
+
+1,2
+
+1,foo,c,1foo
+a,b,c,d
+
+b

test/Twig/Tests/Node/Expression/GetAttrTest.php

@@ -37,7 +37,8 @@ class Twig_Tests_Node_Expression_GetAttrTest extends Twig_Test_NodeTestCase
         $tests[] = array($node, sprintf('%s%s, "bar", array())', $this->getAttributeGetter(), $this->getVariableGetter('foo', 1)));
 
         $node = new Twig_Node_Expression_GetAttr($expr, $attr, $args, Twig_Template::ARRAY_CALL, 1);
-        $tests[] = array($node, sprintf('%s%s, "bar", array(), "array")', $this->getAttributeGetter(), $this->getVariableGetter('foo', 1)));
+        $tests[] = array($node, '(($__internal_%s = // line 1'."\n".
+            '($context["foo"] ?? null)) && is_array($__internal_%s) || $__internal_%s instanceof ArrayAccess ? ($__internal_%s["bar"] ?? null) : null)', null, true);
 
         $args = new Twig_Node_Expression_Array(array(), 1);
         $args->addElement(new Twig_Node_Expression_Name('foo', 1));