Add null-safe operator

[felds]

Adds native support for Twig’s null-safe ?. operator so templates can traverse objects and arrays without defensive plumbing: {{ user?.address?.city }} now renders the value when present and stays silent when any hop is null.

?. reuses the existing GetAttrExpression operator, so it should have otherwise the same precedence and behavior as ..

Usage cases can be found in the tests:

Twig/tests/ExpressionParserTest.php

Lines 304 to 343 in 7d98d45

	[
	'{{ foo?.bar }}',
	['foo' => (object)['bar' => 'baz']],
	'baz',
	],
	[
	'{{ foo?.bar }}',
	['foo' => null],
	'',
	],
	[
	'{{ foo?.bar?.baz }}',
	['foo' => (object)['bar' => (object)['baz' => 'qux']]],
	'qux',
	],
	[
	'{{ foo?.bar?.baz }}',
	['foo' => (object)['bar' => null]],
	'',
	],
	[
	'{{ foo?.bar?.baz }}',
	['foo' => null],
	'',
	],
	[
	'{{ foo?.bar?.baz ?? "qux" }}',
	['foo' => null],
	'qux',
	],
	[
	'{{ foo?.bar ?? "qux" }}',
	['foo' => (object)['bar' => 0]],
	'0',
	],
	[
	'{{ foo?.bar ?? "qux" }}',
	['foo' => (object)['bar' => false]],
	'',
	],

Tests cover both the rendered output and the generated PHP.

Let me know if any tests are missing or if the implementation should be done any other way.

[felds]

This should fix issue #3260

[felds]

The failing tests are already present in twigphp:3.x. I have no idea what they refer to, and I don't think they are related to the changes in this PR.

[felds]

I've found the bug.

It was not in this repo, but it appeared when symfony/intl had some data updated.

I think testing for exact results from dependencies is not a good idea, since it would require updating the tests in this lib every time the depended package was updated, so I changed the test to expect at least N results instead of exactly N results.

[willrowe]

This is a duplicate of #4623

[felds]

@willrowe thanks for pointing that out. I wonder why that PR is stuck. It looks pretty good too...

[johndodev]

up