Fingerprinting and code execution when something changes

Castor provides a fingerprint functionality to execute tasks only if something changed. To detect whether something has changed, Castor uses a fingerprint that can be anything like a string content, the hash of a file or a group of files (based on content or modification time), etc.

The fingerprint() function

You can use the fingerprint() function to conditionally execute a callback if the given fingerprint has changed.

use Castor\Attribute\AsTask;
use function Castor\fingerprint;
use function Castor\io;

#[AsTask(description: 'Execute a callback only if the fingerprint has changed')]
function task_with_a_fingerprint(): void
{
    fingerprint(
        callback: function () {
            io()->writeln('Cool, no fingerprint! Executing...');
        },
        fingerprint: "my fingerprint",
    );
}

Note

You can use the $force parameter of the fingerprint() function to force the execution of the callback even if the fingerprint has not changed.

The hasher() function

Most of the time, you will want your fingerprint hash to be based on the content of a file, to scope it to a specific task or something else. To help you compute this hash, Castor provides a hasher() function. It returns an instance of Castor\Helper\HasherHelper with various helper methods:

• write(): Writes a hash of a specific (string) value.
• writeFile(): Writes a hash of a file content or its modification time.
• writeWithFinder(): Writes a hash of a group of files obtained through Finder.
• writeGlob(): Writes a hash of a group of files obtained via a glob pattern.
• writeTaskName(): Writes the name of the current task.
• writeTaskArgs(): Writes arguments passed to the current task.
• writeTask(): Writes a combination of the current task name and arguments.
• finish(): Finalizes the hash operation, returning a string of the hash.

The methods writeFile(), writeWithFinder() and writeGlob() accept a second parameter $strategy to specify on with criteria the hash should be based on. This parameter is a Castor\Fingerprint\FileHashStrategy enum that contains two values:

• Content will make the hash dependent on the file's content
• MTimes will make the hash depend on the file's last modification time. This is the default strategy.

Example usage:

use Castor\Attribute\AsTask;
use Castor\Fingerprint\FileHashStrategy;
use function Castor\fingerprint;
use function Castor\hasher;

#[AsTask(description: 'Execute a callback only if the fingerprint has changed')]
function task_with_a_fingerprint(): void
{
    fingerprint(
        callback: function () {
            io()->writeln('Executing the callback because my-file.json has changed.');
        },
        fingerprint: hasher()->writeFile('my-file.json', FileHashStrategy::Content)->finish(),
    );
}

The fingerprint_exists() and fingerprint_save() functions

If you want more control over the fingerprint behaviour, you can use the fingerprint_exists() and fingerprint_save() functions to conditionally execute your code:

use Castor\Attribute\AsTask;
use Castor\Fingerprint\FileHashStrategy;
use function Castor\finder;
use function Castor\fingerprint_exists;
use function Castor\fingerprint_save;
use function Castor\hasher;

#[AsTask(description: 'Check if the fingerprint has changed before executing some code')]
function task_with_some_fingerprint(): void
{
    if (!fingerprint_exists(my_fingerprint_check())) {
        io()->writeln('Executing some code because fingerprint has changed.');
        fingerprint_save(my_fingerprint_check());
    }
}

function my_fingerprint_check(): string
{
    return hasher()
        ->writeWithFinder(
            finder()
                ->in(__DIR__)
                ->name('*.json')
                ->files(),
            FileHashStrategy::Content
        )
        ->finish();
}