在flask-assets (webassets)中编写自定义过滤器

Question

使用Flask和flask-assets (来自webassets)，我为css压缩器following the documentation编写了自己的自定义过滤器。它似乎不起作用：

from csscompressor import compress
from flask_assets import Bundle
from webassets.filter import Filter, register_filter

class NoopFilter(Filter):
    name = 'csscompressor'
    print("noopfilter")

    def output(self, _in, out, **kwargs):
        print("output")

    def input(self, _in, out, **kwargs):
        print("input")

register_filter(NoopFilter)

bundles = {
    'home_css': Bundle(
        'css/main.css',
        'css/forms.css',
        output='gen/home.css',
        filters='csscompressor'
    )

该类在启动时被调用两次，过滤器是通过它的名称找到的，但input()或output()似乎从未被调用过。css文件被创建，但显然没有任何压缩。有没有人有这方面的经验？

Answer 1

显然，这是一个缓存问题。更改筛选器名称可使其正常工作。希望这能帮助一些人在一些kB上拔出他们的头发。

Answer 2

使用CSS压缩器包压缩CSS的示例(pip install CSS压缩器)

from csscompressor import compress
from flask_assets import Bundle
from webassets.filter import Filter, register_filter

class NoopFilter(Filter):
    name = 'css_compress'

    def output(self, _in, out, **kwargs):
        css = compress(_in.read())
        out.write(css)

    def input(self, _in, out, **kwargs):
        css = compress(_in.read())
        out.write(css)


register_filter(NoopFilter)


bundles = {
    'app_css': Bundle(
        'css/responsive.css',
        'css/ads.css',
         filters='css_compress',
         output='all/app.css'
    ),