bug #4778 Fix null coalescing operator with imported macros (fabpot)

This PR was merged into the 3.x branch.

Discussion
----------

Fix null coalescing operator with imported macros

Closes #4776

When using the null coalescing operator with a macro imported via the `from` tag, the `TemplateVariable` node inside `MacroReferenceExpression` was deep-cloned, causing the clone to generate a different `$macros` key than the one assigned by `AssignTemplateVariable`. This resulted in a `Call to a member function hasMacro() on null` error.

Commits
-------

efa004c Fix null coalescing operator with imported macros

Author: fabpot

src/Node/Expression/MacroReferenceExpression.php

@@ -29,6 +29,16 @@ public function __construct(TemplateVariable $template, string $name, AbstractEx
         parent::__construct(['template' => $template, 'arguments' => $arguments], ['name' => $name], $lineno);
     }
 
+    public function __clone()
+    {
+        // The template node must not be deep-cloned because its name is
+        // lazily generated during compilation and must stay in sync with
+        // the AssignTemplateVariable that populates the $macros array.
+        $template = $this->nodes['template'];
+        parent::__clone();
+        $this->nodes['template'] = $template;
+    }
+
     public function compile(Compiler $compiler): void
     {
         if ($this->definedTest) {

tests/TemplateTest.php

@@ -150,6 +150,43 @@ public static function getRenderTemplateWithoutOutputData()
         ];
     }
 
+    /**
+     * @dataProvider getNullCoalesceWithImportedMacroData
+     */
+    public function testNullCoalesceWithImportedMacro(array $templates, string $expected)
+    {
+        $twig = new Environment(new ArrayLoader($templates));
+
+        $this->assertSame($expected, trim($twig->render('index.twig')));
+    }
+
+    public static function getNullCoalesceWithImportedMacroData(): array
+    {
+        return [
+            'from import' => [
+                [
+                    'index.twig' => '{% from "helper.twig" import foo %}{{ foo("bar") ?? "" }}',
+                    'helper.twig' => '{% macro foo(param) %}{{ param }}{% endmacro %}',
+                ],
+                'bar',
+            ],
+            'from import with undefined macro falls back' => [
+                [
+                    'index.twig' => '{% from "helper.twig" import foo, nonexistent %}{{ nonexistent("bar") ?? "fallback" }}',
+                    'helper.twig' => '{% macro foo(param) %}{{ param }}{% endmacro %}',
+                ],
+                'fallback',
+            ],
+            'from import used multiple times' => [
+                [
+                    'index.twig' => '{% from "helper.twig" import foo %}{{ foo("a") ?? "" }}-{{ foo("b") ?? "" }}',
+                    'helper.twig' => '{% macro foo(param) %}{{ param }}{% endmacro %}',
+                ],
+                'a-b',
+            ],
+        ];
+    }
+
     public function testRenderBlockWithUndefinedBlock()
     {
         $twig = new Environment(new ArrayLoader());