minor #4133 Simplify Loop code (fabpot)

This PR was squashed before being merged into the 4.x branch.

Discussion
----------

Simplify Loop code

Let's compute values as late as possible.

Commits
-------

437ad31d Move some code to LoopContext
0c2a69ce Simplify Loop code

src/Node/ForNode.php

@@ -44,11 +44,11 @@ class ForNode extends Node
             ->write("\$context['_parent'] = \$context;\n")
             ->write("\$$loopName = new \Twig\Runtime\Loop(")
             ->subcompile($this->getNode('seq'))
-            ->raw(", \$context['_parent']);\n")
+            ->raw(");\n")
         ;
 
         if ($this->getAttribute('with_loop')) {
-            $compiler->write("\$context['loop'] = new \Twig\Runtime\LoopContext(\${$loopName});\n");
+            $compiler->write("\$context['loop'] = new \Twig\Runtime\LoopContext(\${$loopName}, \$context['_parent']);\n");
         }
 
         $compiler

src/Runtime/Loop.php

@@ -23,14 +23,10 @@ use Twig\Error\RuntimeError;
 final class Loop implements \Iterator
 {
     private \Iterator $seq;
-    private bool $iterated;
     private int $index0;
-    private int $revindex0;
-    private bool $first;
-    private bool $last;
     private int $length;
 
-    public function __construct($seq, private $parent)
+    public function __construct($seq)
     {
         $this->seq = is_iterable($seq) ? (is_array($seq) ? new \ArrayIterator($seq) : $seq) : new \ArrayIterator([]);
         $this->rewind();
@@ -49,29 +45,13 @@ final class Loop implements \Iterator
     public function next(): void
     {
         $this->seq->next();
-
-        $this->iterated = true;
         ++$this->index0;
-        $this->first = false;
-        if (isset($this->length)) {
-            --$this->revindex0;
-            $this->last = 0 === $this->revindex0;
-        }
     }
 
     public function rewind(): void
     {
         $this->seq->rewind();
-
-        $this->iterated = false;
         $this->index0 = 0;
-        $this->first = true;
-        if ($this->seq instanceof \Countable) {
-            $length = count($this->seq);
-            $this->revindex0 = $length - 1;
-            $this->length = $length;
-            $this->last = 1 === $length;
-        }
     }
 
     public function valid(): bool
@@ -81,21 +61,7 @@ final class Loop implements \Iterator
 
     public function iterated(): bool
     {
-        return $this->iterated;
-    }
-
-    public function getParent(): mixed
-    {
-        return $this->parent;
-    }
-
-    public function getRevindex0(): int
-    {
-        if (!$this->seq instanceof \Countable) {
-            throw new RuntimeError('The "loop.revindex0" variable is not defined as the loop iterates on a non-countable iterator.');
-        }
-
-        return $this->revindex0;
+        return 0 !== $this->index0;
     }
 
     public function getIndex0(): int
@@ -103,26 +69,16 @@ final class Loop implements \Iterator
         return $this->index0;
     }
 
-    public function getLength(): int
+    public function getLength($var = 'length'): int
     {
-        if (!$this->seq instanceof \Countable) {
-            throw new RuntimeError('The "loop.length" variable is not defined as the loop iterates on a non-countable iterator.');
+        if (isset($this->length)) {
+            return $this->length;
         }
 
-        return $this->length;
-    }
-
-    public function isFirst(): bool
-    {
-        return $this->first;
-    }
-
-    public function isLast(): bool
-    {
         if (!$this->seq instanceof \Countable) {
-            throw new RuntimeError('The "loop.last" variable is not defined as the loop iterates on a non-countable iterator.');
+            throw new RuntimeError(sprintf('The "loop.%s" variable is not defined as the loop iterates on a non-countable iterator.', $var));
         }
 
-        return $this->last;
+        return $this->length = count($this->seq);
     }
 }

src/Runtime/LoopContext.php

@@ -20,23 +20,23 @@ namespace Twig\Runtime;
  */
 final class LoopContext
 {
-    public function __construct(private Loop $loop)
+    public function __construct(private Loop $loop, private $parent)
     {
     }
 
     public function getParent(): mixed
     {
-        return $this->loop->getParent();
+        return $this->parent;
     }
 
     public function getRevindex0(): int
     {
-        return $this->loop->getRevindex0();
+        return $this->loop->getLength('revindex0') - $this->getIndex();
     }
 
     public function getRevindex(): int
     {
-        return $this->loop->getRevindex0() + 1;
+        return $this->loop->getLength('revindex') - $this->getIndex0();
     }
 
     public function getIndex0(): int
@@ -56,11 +56,11 @@ final class LoopContext
 
     public function isFirst(): bool
     {
-        return $this->loop->isFirst();
+        return 0 === $this->getIndex0();
     }
 
     public function isLast(): bool
     {
-        return $this->loop->isLast();
+        return 0 === $this->loop->getLength('last') - $this->getIndex();
     }
 }

tests/Fixtures/tags/for/loop_context.test

@@ -4,16 +4,20 @@
 {% for item in items %}
   * {{ loop.index }}/{{ loop.index0 }}
   * {{ loop.revindex }}/{{ loop.revindex0 }}
-  * {{ loop.first }}/{{ loop.last }}/{{ loop.length }}
+  * {{ loop.first ? 'FIRST' : '-' }}/{{ loop.last ? 'LAST' : '-' }}/{{ loop.length }}
 
 {% endfor %}
 --DATA--
-return ['items' => ['a', 'b']]
+return ['items' => ['a', 'b', 'c']]
 --EXPECT--
   * 1/0
-  * 2/1
-  * 1//2
+  * 3/2
+  * FIRST/-/3
 
   * 2/1
+  * 2/1
+  * -/-/3
+
+  * 3/2
   * 1/0
-  * /1/2
+  * -/LAST/3

tests/Fixtures/tags/for/non_countable.test

@@ -2,7 +2,7 @@
 "for" tag loop variable throws when last is used on a non-countable
 --TEMPLATE--
 {% for item in items %}
-  * {{ loop.last }}
+  * {{ loop.revindex }}
 {% endfor %}
 --DATA--
 class ItemsIteratorNotCountable implements \Iterator
@@ -16,4 +16,4 @@ class ItemsIteratorNotCountable implements \Iterator
 }
 return ['items' => new ItemsIteratorNotCountable()]
 --EXCEPTION--
-Twig\Error\RuntimeError: The "loop.last" variable is not defined as the loop iterates on a non-countable iterator in "index.twig" at line 3.
+Twig\Error\RuntimeError: The "loop.revindex" variable is not defined as the loop iterates on a non-countable iterator in "index.twig" at line 3.

tests/Node/ForTest.php

@@ -57,7 +57,7 @@ class ForTest extends NodeTestCase
         $tests[] = [$node, <<<EOF
 // line 1
 \$context['_parent'] = \$context;
-\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('items')}, \$context['_parent']);
+\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('items')});
 foreach (\$__internal_compile_0 as \$context["key"] => \$context["item"]) {
     yield {$this->getVariableGetter('foo')};
 }
@@ -78,8 +78,8 @@ EOF
         $tests[] = [$node, <<<EOF
 // line 1
 \$context['_parent'] = \$context;
-\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')}, \$context['_parent']);
-\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0);
+\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')});
+\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0, \$context['_parent']);
 foreach (\$__internal_compile_0 as \$context["k"] => \$context["v"]) {
     yield {$this->getVariableGetter('foo')};
 }
@@ -100,8 +100,8 @@ EOF
         $tests[] = [$node, <<<EOF
 // line 1
 \$context['_parent'] = \$context;
-\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')}, \$context['_parent']);
-\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0);
+\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')});
+\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0, \$context['_parent']);
 foreach (\$__internal_compile_0 as \$context["k"] => \$context["v"]) {
     yield {$this->getVariableGetter('foo')};
 }
@@ -122,8 +122,8 @@ EOF
         $tests[] = [$node, <<<EOF
 // line 1
 \$context['_parent'] = \$context;
-\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')}, \$context['_parent']);
-\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0);
+\$__internal_compile_0 = new \Twig\Runtime\Loop({$this->getVariableGetter('values')});
+\$context['loop'] = new \Twig\Runtime\LoopContext(\$__internal_compile_0, \$context['_parent']);
 foreach (\$__internal_compile_0 as \$context["k"] => \$context["v"]) {
     yield {$this->getVariableGetter('foo')};
 }