compiler.py 文件源码

def compiles(class_, *specs):
    """Register a function as a compiler for a
    given :class:`.ClauseElement` type."""

    def decorate(fn):
        existing = class_.__dict__.get('_compiler_dispatcher', None)
        existing_dispatch = class_.__dict__.get('_compiler_dispatch')
        if not existing:
            existing = _dispatcher()

            if existing_dispatch:
                existing.specs['default'] = existing_dispatch

            # TODO: why is the lambda needed ?
            setattr(class_, '_compiler_dispatch',
                    lambda *arg, **kw: existing(*arg, **kw))
            setattr(class_, '_compiler_dispatcher', existing)

        if specs:
            for s in specs:
                existing.specs[s] = fn

        else:
            existing.specs['default'] = fn
        return fn
    return decorate