in src/CodegenFile.hack [63:77]
public function __construct(
private IHackCodegenConfig $config,
string $file_name,
) {
$root = $config->getRootDir();
if (!Str\starts_with($file_name, '/')) {
$this->relativeFileName = $file_name;
$file_name = $root.'/'.$file_name;
} else if (Str\starts_with($file_name, $root)) {
$this->relativeFileName = Str\slice($file_name, Str\length($root) + 1);
} else {
$this->relativeFileName = $file_name;
}
$this->fileName = $file_name;
}