Function run_plugins 

pub fn run_plugins(
    directives: &mut Vec<Spanned<Directive>>,
    file_plugins: &[Plugin],
    file_options: &Options,
    options: &LoadOptions,
    source_map: &SourceMap,
    errors: &mut Vec<LedgerError>,
    pass: PluginPass,
) -> Result<(), ProcessError>

pass selects which subset of plugins to run — see PluginPass. The loader pipeline calls this twice (synth pass before Early, regular pass after booking).