我们可以在编译时使用twig删除空格，而不是在渲染时删除它吗？

Question

Twig has the {% spaceless %} tag, which removes all the white space between HTML tags.

However, it does this with a preg_replace when you render the template. Fine on small files, but if you have a large complex template there's a performance hit.

I feel like it should be possible to strip the whitespace out at compile time?

My compiled template is full of stuff like

        echo "    <h2>Heading</h2>
";

Where the template has included the following:

<section>
    <h2>Heading</h2>
</section>

What I want on the final rendered HTML is

<section><h2>Heading</h2></section>

Why couldn't twig (very simply) add a trim in when building the compiled template, to give us:

echo "<h2>Heading</h2>";

in the compiled template php code.

I get that there could still be whitespace in whatever data I populate the template with inside {{ }}, but I can control that from my PHP easily.

Answer 1

OK, after much digging in the library trying to work out which files generate which bits of the output, I've finally found this "fix".

Change

->string($this->getAttribute('data'))

to

->string(trim(preg_replace('/>\s+</', '><', $this->getAttribute('data'))))

On line 30 of /lib/Twig/Node/Text.php.

Doing that correctly gives me a "spaceless" output, but without requiring the expensive template-render-time preg_replace call.

Will it cause problems? Possibly in some use cases, maybe with a partial <pre> or <textarea> tag. I can't see either of those being an issue for me though.

Any gotchas that I've not thought of?