[Php] Add NullCoalescingOperatorRector

packages/Php/src/Rector/Assign/NullCoalescingOperatorRector.php

@@ -0,0 +1,60 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Php\Rector\Assign;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\Assign;
+use PhpParser\Node\Expr\BinaryOp\Coalesce;
+use Rector\Rector\AbstractRector;
+use Rector\RectorDefinition\CodeSample;
+use Rector\RectorDefinition\RectorDefinition;
+
+/**
+ * @see https://wiki.php.net/rfc/null_coalesce_equal_operator
+ */
+final class NullCoalescingOperatorRector extends AbstractRector
+{
+    public function getDefinition(): RectorDefinition
+    {
+        return new RectorDefinition('Use null coalescing operator ??=', [
+            new CodeSample(
+                <<<'CODE_SAMPLE'
+$array = [];
+$array['user_id'] = $array['user_id'] ?? 'value';
+CODE_SAMPLE
+                ,
+                <<<'CODE_SAMPLE'
+$array = [];
+$array['user_id'] ??= 'value';
+CODE_SAMPLE
+            ),
+        ]);
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getNodeTypes(): array
+    {
+        return [Assign::class];
+    }
+
+    /**
+     * @param Assign $node
+     */
+    public function refactor(Node $node): ?Node
+    {
+        if (! $node->expr instanceof Coalesce) {
+            return null;
+        }
+
+        if (! $this->areNodesEqual($node->var, $node->expr->left)) {
+            return null;
+        }
+
+        $coalesceNode = new Coalesce($node->var, $node->expr->right);
+        $coalesceNode->setAttribute('null_coalesce', true);
+
+        return $coalesceNode;
+    }
+}

packages/Php/tests/Rector/Assign/NullCoalescingOperatorRector/Fixture/fixture.php.inc

@@ -0,0 +1,15 @@
+<?php
+
+$array = [];
+$array['user_id'] = $array['user_id'] ?? 'value';
+$array['user_id'] = $array['user_id_'] ?? 'value';
+
+?>
+-----
+<?php
+
+$array = [];
+$array['user_id'] ??= 'value';
+$array['user_id'] = $array['user_id_'] ?? 'value';
+
+?>

packages/Php/tests/Rector/Assign/NullCoalescingOperatorRector/NullCoalescingOperatorRectorTest.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Php\Tests\Rector\Assign\NullCoalescingOperatorRector;
+
+use Rector\Php\Rector\Assign\NullCoalescingOperatorRector;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class NullCoalescingOperatorRectorTest extends AbstractRectorTestCase
+{
+    public function test(): void
+    {
+        $this->doTestFiles([__DIR__ . '/Fixture/fixture.php.inc']);
+    }
+
+    protected function getRectorClass(): string
+    {
+        return NullCoalescingOperatorRector::class;
+    }
+}

src/PhpParser/Printer/BetterStandardPrinter.php

@@ -6,6 +6,7 @@ use Nette\Utils\Strings;
 use PhpParser\Node;
 use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\Array_;
+use PhpParser\Node\Expr\BinaryOp\Coalesce;
 use PhpParser\Node\Expr\Closure;
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\MethodCall;
@@ -214,6 +215,18 @@ final class BetterStandardPrinter extends Standard
             . ($node->stmts !== null ? $this->nl . '{' . $this->pStmts($node->stmts) . $this->nl . '}' : ';');
     }
 
+    /**
+     * Print ??= since PHP 7.4
+     */
+    protected function pExpr_BinaryOp_Coalesce(Coalesce $node): string
+    {
+        if (! $node->getAttribute('null_coalesce')) {
+            return parent::pExpr_BinaryOp_Coalesce($node);
+        }
+
+        return $this->pInfixOp(Coalesce::class, $node->left, ' ??= ', $node->right);
+    }
+
     /**
      * Allows PHP 7.3 trailing comma in multiline args
      *