Illuminate\View\Compilers\Compiler::isExpired should cache results -- huge optimization benefit!

[skeets23]

Currently, there is no cache mechanism in Illuminate\View\Compilers\Compiler::isExpired, so if you include a view 10,000 times in your output (very possible if you have a super modular design, or a table / row / cell set up with lots of rows), it will literally check if the file exists 10,000 times and execute filemtime 20,000 times (checking both target and source creation dates).

I ran into this when I discovered (using xdebug profiling) that the "isExpired" function is the biggest bottleneck I have on a datagrid I have created, were the "cell" blade on the lowest level of the blade is used many thousand times (our customers like to have a lot of rows visible at once)

I attempted to add a cache in Illuminate/View/Compilers/Compiler.php like so:

public function isExpired($path)
{
    static $cache = [];

    $compiled = $this->getCompiledPath($path);

    if (isset($cache[$path])) {
        return $cache[$path];
    }

    // If the compiled file doesn't exist we will indicate that the view is expired
    // so that it can be re-compiled. Else, we will verify the last modification
    // of the views is less than the modification times of the compiled views.
    if ( ! $this->files->exists($compiled)) {
        $cache[$path] = true;

        return true;
    }

    $cache[$path] = $this->files->lastModified($path) >= $this->files->lastModified($compiled);

    return $cache[$path];
}

Using xdebug, I can see that adding the cache dropped the time spent in this function dramatically.

Without cache: 43.46% of total time
With cache: 1.32% of total time

43% -> 1%!! it seems like adding a cache would be worth it for such a huge difference.