Integrate Latte into Laravel directly without using a package

app.php

<?php

return [
    'providers' => [
        App\Providers\LatteProvider::class
    ]
];

composer.json

{
    "require": {
        "latte/latte": "^2.0"
    }
}

LatteProvider.php

<?php

namespace App\Providers;

use Illuminate\Contracts\View\Factory;
use Illuminate\Foundation\Application;
use Illuminate\Support\ServiceProvider;
use Illuminate\Support\Str;
use Latte\Engine;
use Latte\Macros\MacroSet;

class LatteProvider extends ServiceProvider
{
    public function register(): void
    {
        $this->app->singleton('latte.engine', function ($app) {
            $latte = $this->createEngine($app);
            $this->installMacros($latte);
            $this->installFilters($latte);
            return $latte;
        });

        $this->app->resolving('view', function (Factory $viewFactory, Application $app) {
            return $this->resolveView($viewFactory, $app);
        });
    }

    protected function createEngine(Application $app): Engine
    {
        $isDebug = $app['config']['app.debug'];
        $compiledViewsDir = $app['config']['view.compiled'];
        $mainViewDir = $app['config']['view.paths.0'];

        $latte = new Engine;
        $latte->setAutoRefresh($isDebug);
        $latte->setTempDirectory($compiledViewsDir);
        $latte->setLoader(new LatteProviderFileLoader($mainViewDir));

        return $latte;
    }

    protected function resolveView(Factory $viewFactory, Application $app): void
    {
        if (! ($viewFactory instanceof \Illuminate\View\Factory)) {
            $class = get_class($viewFactory);
            throw new \InvalidArgumentException("Can't register Latte\Engine: {$class} is not supported.");
        }
        $resolver = fn() => new LatteProviderEngineBridge($app['latte.engine']);
        $viewFactory->addExtension('latte', 'latte', $resolver);
    }

    protected function installMacros(Engine $latte): void
    {
        $macros = new MacroSet($latte->getCompiler());

        // Allow injecting sections à la Blade
        $macros->addMacro('yield', 'echo $__env->yieldContent(%node.word);');
    }

    protected function installFilters(Engine $latte): void
    {
        // Slug filter
        $latte->addFilter('slug', fn($string) => Str::slug($string));

        // Retrieve translation string
        $latte->addFilter('translate', function ($key, $replace = [], $locale = null) {
            if (is_string($replace) && ! $locale) {
                $locale = $replace;
                $replace = [];
            }

            return __($key, $replace, $locale);
        });
    }
}

LatteProviderEngineBridge.php

<?php

namespace App\Providers;

use Illuminate\Contracts\View\Engine as EngineInterface;
use Latte\Engine;

class LatteProviderEngineBridge implements EngineInterface
{
    private $latte;

    public function __construct(Engine $latte)
    {
        $this->latte = $latte;
    }

    public function get($path, array $data = []): string
    {
        return $this->latte->renderToString($path, $data);
    }
}

LatteProviderFileLoader.php

<?php

namespace App\Providers;

use Illuminate\Support\Str;
use Latte\Loaders\FileLoader;

class LatteProviderFileLoader extends FileLoader
{
    public function getContent($fileName): string
    {
        // Remove base dir from beginning
        if ($this->baseDir) {
            $fileName = Str::after($fileName, $this->baseDir);
        }
        // Allow dot syntax for folders
        $fileName = Str::before($fileName, '.latte');
        $fileName = str_replace('.', '/', $fileName);
        $fileName = "{$fileName}.latte";

        return parent::getContent($fileName);
    }

    public function getReferredName($file, $referringFile): string
    {
        return $file;
    }
}