Macro arguments using leading/tailing underscore (BC introduced in v3.15)

[kampalex]

Hi. I discovered a side effect after upgrading to the latest version, related to this line in PR 4391.
For me, it's a BC, which may affect others as well.
The usage of macro arguments having leading/tailing underscores worked well until 3.15.

Example:

{% macro testing(_message) %}
The message: '{{ _message }}'.
{% endmacro %}
{{ _self.testing('Hello World!') }}

Output:
3.14: The message: 'Hello World!'.
3.15: The message: ''.

Compiled template:
In the referred line of the PR, underscores are trimmed off from arguments as they are assigned onto $context. _message becomes message, but the original _message is requested in the escape-method later. That's an error.

[...]
class __TwigTemplate_[...] extends Template
[...]
    // line 1
    public function macro_testing($_message = null, ...$varargs): string|Markup
    {
        $macros = $this->macros;
        $context = [
            "message" => $_message,
            "varargs" => $varargs,
        ] + $this->env->getGlobals();

        $blocks = [];

        return ('' === $tmp = \Twig\Extension\CoreExtension::captureOutput((function () use (&$context, $macros, $blocks) {
            // line 2
            yield "The message: '";
            yield $this->env->getRuntime('Twig\Runtime\EscaperRuntime')->escape(($context["_message"] ?? null), "html", null, true);
            yield "'.
";
            yield from [];
        })())) ? '' : new Markup($tmp, $this->env->getCharset());
    }

I'm curious how I should see the code change. If this is the intention, maybe a trigger_deprecation should be called while evaluating the macro arguments.
I just wanted to let you know - the affected templates will be fixed on my side.

[stof]

@fabpot what was the reason to trim _ in the names ?

[kampalex]

In v3.14.2...v3.15.0 diff:

File doc/coding_standards.rst:
Line 91 | Old: * Use lower cased and underscored variable names:
Line 91 | New: * Use snake case for all variable names (provided by the application and created in templates):
[....]
Added: * Use snake case for all function/filter/test names:

....Okay! This explanation has clarified my issue.

The compiled template looks much cleaner without the __ wrap per macro argument:
3.14: public function macro_testing($___message__ = null, ...$__varargs__)
3.15: public function macro_testing($_message = null, ...$varargs): string|Markup
According to the doc changes, _message as macro argument is deprecated.

I think the reason for trim is RESERVED_NAMES which are wrapped using '_'.

[mathieu-dumoutier]

Hello. I have an error too when I upgraded 3.14.2 to 3.15

An exception has been thrown during the rendering of a template ("Warning: Undefined variable $_v0"). on each rendered of easyadmin's crud routes (4.15.1)

Like the missing variable is $_v0 with an underscore, I think is may be in relation with this issue. It seems to appear with |trans filter.

[fabpot]

#4475 should fix this issue