symfony · fabpot · Jul 25, 2022 · Apr 18, 2022 · syntaxerro · Apr 19, 2023
diff --git a/src/Symfony/Component/ExpressionLanguage/CHANGELOG.md b/src/Symfony/Component/ExpressionLanguage/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 6.1
 ---
 
+ * Add support for null-coalescing syntax
  * Add support for null-safe syntax when parsing object's methods and properties
  * Add new operators: `contains`, `starts with` and `ends with`
  * Support lexing numbers with the numeric literal separator `_`

diff --git a/src/Symfony/Component/ExpressionLanguage/Lexer.php b/src/Symfony/Component/ExpressionLanguage/Lexer.php
@@ -77,6 +77,10 @@ public function tokenize(string $expression): TokenStream
                 // null-safe
                 $tokens[] = new Token(Token::PUNCTUATION_TYPE, '?.', ++$cursor);
                 ++$cursor;
+            } elseif ('?' === $expression[$cursor] && '?' === ($expression[$cursor + 1] ?? '')) {
+                // null-coalescing
+                $tokens[] = new Token(Token::PUNCTUATION_TYPE, '??', ++$cursor);
+                ++$cursor;
             } elseif (str_contains('.,?:', $expression[$cursor])) {
                 // punctuation
                 $tokens[] = new Token(Token::PUNCTUATION_TYPE, $expression[$cursor], $cursor + 1);

diff --git a/src/Symfony/Component/ExpressionLanguage/Node/GetAttrNode.php b/src/Symfony/Component/ExpressionLanguage/Node/GetAttrNode.php
@@ -25,6 +25,7 @@ class GetAttrNode extends Node
     public const ARRAY_CALL = 3;
 
     private bool $isShortCircuited = false;
+    public bool $isNullCoalesce = false;
 
     public function __construct(Node $node, Node $attribute, ArrayNode $arguments, int $type)
     {
@@ -72,8 +73,7 @@ public function evaluate(array $functions, array $values)
         switch ($this->attributes['type']) {
             case self::PROPERTY_CALL:
                 $obj = $this->nodes['node']->evaluate($functions, $values);
-
-                if (null === $obj && $this->nodes['attribute']->isNullSafe) {
+                if (null === $obj && ($this->nodes['attribute']->isNullSafe || $this->isNullCoalesce)) {
                     $this->isShortCircuited = true;
 
                     return null;
@@ -88,6 +88,10 @@ public function evaluate(array $functions, array $values)
 
                 $property = $this->nodes['attribute']->attributes['value'];
 
+                if ($this->isNullCoalesce) {
+                    return $obj->$property ?? null;
+                }
+
                 return $obj->$property;
 
             case self::METHOD_CALL:
@@ -118,10 +122,14 @@ public function evaluate(array $functions, array $values)
                     return null;
                 }
 
-                if (!\is_array($array) && !$array instanceof \ArrayAccess) {
+                if (!\is_array($array) && !$array instanceof \ArrayAccess && !(null === $array && $this->isNullCoalesce)) {
                     throw new \RuntimeException(sprintf('Unable to get an item of non-array "%s".', $this->nodes['node']->dump()));
                 }
 
+                if ($this->isNullCoalesce) {
+                    return $array[$this->nodes['attribute']->evaluate($functions, $values)] ?? null;
+                }
+
                 return $array[$this->nodes['attribute']->evaluate($functions, $values)];
         }
     }

diff --git a/src/Symfony/Component/ExpressionLanguage/Node/NullCoalesceNode.php b/src/Symfony/Component/ExpressionLanguage/Node/NullCoalesceNode.php
@@ -0,0 +1,52 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ExpressionLanguage\Node;
+
+use Symfony\Component\ExpressionLanguage\Compiler;
+
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @internal
+ */
+class NullCoalesceNode extends Node
+{
+    public function __construct(Node $expr1, Node $expr2)
+    {
+        parent::__construct(['expr1' => $expr1, 'expr2' => $expr2]);
+    }
+
+    public function compile(Compiler $compiler)
+    {
+        $compiler
+            ->raw('((')
+            ->compile($this->nodes['expr1'])
+            ->raw(') ?? (')
+            ->compile($this->nodes['expr2'])
+            ->raw('))')
+        ;
+    }
+
+    public function evaluate(array $functions, array $values)
+    {
+        if ($this->nodes['expr1'] instanceof GetAttrNode) {
+            $this->nodes['expr1']->isNullCoalesce = true;
+        }
+
+        return $this->nodes['expr1']->evaluate($functions, $values) ?? $this->nodes['expr2']->evaluate($functions, $values);
+    }
+
+    public function toArray()
+    {
+        return ['(', $this->nodes['expr1'], ') ?? (', $this->nodes['expr2'], ')'];
+    }
+}
diff --git a/src/Symfony/Component/ExpressionLanguage/Parser.php b/src/Symfony/Component/ExpressionLanguage/Parser.php
@@ -176,6 +176,13 @@ protected function getPrimary()
 
     protected function parseConditionalExpression(Node\Node $expr)
     {
+        while ($this->stream->current->test(Token::PUNCTUATION_TYPE, '??')) {
+            $this->stream->next();
+            $expr2 = $this->parseExpression();
+
+            $expr = new Node\NullCoalesceNode($expr, $expr2);
+        }
+
         while ($this->stream->current->test(Token::PUNCTUATION_TYPE, '?')) {
             $this->stream->next();
             if (!$this->stream->current->test(Token::PUNCTUATION_TYPE, ':')) {

diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php
@@ -315,6 +315,44 @@ public function provideInvalidNullSafe()
         yield ['foo?.bar["baz"].qux.quux', (object) ['bar' => ['baz' => null]], 'Unable to get property "qux" of non-object "foo.bar["baz"]".'];
     }
 
+    /**
+     * @dataProvider provideNullCoalescing
+     */
+    public function testNullCoalescingEvaluate($expression, $foo)
+    {
+        $expressionLanguage = new ExpressionLanguage();
+        $this->assertSame($expressionLanguage->evaluate($expression, ['foo' => $foo]), 'default');
+    }
+
+    /**
+     * @dataProvider provideNullCoalescing
+     */
+    public function testNullCoalescingCompile($expression, $foo)
+    {
+        $expressionLanguage = new ExpressionLanguage();
+        $this->assertSame(eval(sprintf('return %s;', $expressionLanguage->compile($expression, ['foo' => 'foo']))), 'default');
+    }
+
+    public function provideNullCoalescing()
+    {
+        $foo = new class() extends \stdClass {
+            public function bar()
+            {
+                return null;
+            }
+        };
+
+        yield ['foo.bar ?? "default"', null];
+        yield ['foo.bar.baz ?? "default"', (object) ['bar' => null]];
+        yield ['foo.bar ?? foo.baz ?? "default"', null];
+        yield ['foo[0] ?? "default"', []];
+        yield ['foo["bar"] ?? "default"', ['bar' => null]];
+        yield ['foo["baz"] ?? "default"', ['bar' => null]];
+        yield ['foo["bar"]["baz"] ?? "default"', ['bar' => null]];
+        yield ['foo["bar"].baz ?? "default"', ['bar' => null]];
+        yield ['foo.bar().baz ?? "default"', $foo];
+    }
+
     /**
      * @dataProvider getRegisterCallbacks
      */

diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
@@ -163,6 +163,16 @@ public function getParseData()
                 'foo?.not()',
                 ['foo'],
             ],
+            [
+                new Node\NullCoalesceNode(new Node\GetAttrNode(new Node\NameNode('foo'), new Node\ConstantNode('bar', true), new Node\ArgumentsNode(), Node\GetAttrNode::PROPERTY_CALL), new Node\ConstantNode('default')),
+                'foo.bar ?? "default"',
+                ['foo'],
+            ],
+            [
+                new Node\NullCoalesceNode(new Node\GetAttrNode(new Node\NameNode('foo'), new Node\ConstantNode('bar'), new Node\ArgumentsNode(), Node\GetAttrNode::ARRAY_CALL), new Node\ConstantNode('default')),
+                'foo["bar"] ?? "default"',
+                ['foo'],
+            ],
 
             // chained calls
             [