OSError：[Errno 78]函数未实现Flask-Assets

Question

当我使用Flask-Assets访问一个URL时，我得到了下面的错误，这个URL应该渲染和缩小css。

ERROR    2016-09-01 02:45:00,096 app.py:1587] Exception on /SomeFile [GET]
Traceback (most recent call last):
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/app.py", line 1988, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/app.py", line 1641, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/app.py", line 1544, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/app.py", line 1639, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/app.py", line 1625, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/vinay/App-Engine/zion-alpha/app/routes/home_routes.py", line 14, in show_file
    return render_template('main.html')
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/templating.py", line 134, in render_template
    context, ctx.app)
  File "/Users/vinay/App-Engine/zion-alpha/lib/flask/templating.py", line 116, in _render
    rv = template.render(context)
  File "/Users/vinay/App-Engine/zion-alpha/lib/jinja2/environment.py", line 989, in render
    return self.environment.handle_exception(exc_info, True)
  File "/Users/vinay/App-Engine/zion-alpha/lib/jinja2/environment.py", line 754, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/vinay/App-Engine/zion-alpha/app/templates/main.html", line 6, in top-level template code
    {% assets "css_all" %}
OSError: [Errno 78] Function not implemented
INFO     2016-09-01 02:45:00,116 module.py:788] default: "GET /SomeFile HTTP/1.1" 500 291
INFO     2016-09-01 02:45:00,853 module.py:402] [default] Detected file changes:
  /Users/vinay/App-Engine/zion-alpha/app

以下是包含Flask-Assets的代码

def create_app():
    """Create the Flask App"""
    app = Flask(__name__)
    configure_blueprints(app)
    css = Bundle('css/main.css',
                 'css/main2.css',
                 filters="cssmin",
                 output="static/css/min.css"
                 )
    assets = Environment(app)
    assets.register('css_all', css)
    return app

HTML

{% assets "css_all" %}
    <link rel="stylesheet" href="{{ ASSET_URL }}"/>
{% endassets %}

文件夹结构

.
├── admin
│   ├── __init__.py
│   ├── __init__.pyc
│   ├── routes
│   │   ├── __init__.py
│   │   ├── __init__.pyc
│   │   ├── admin_routes.py
│   │   └── admin_routes.pyc
│   ├── static
│   │   └── css
│   │       ├── admin-2.css
│   │       └── admin.css
│   └── templates
│       └── adminindex.html
├── app
│   ├── __init__.py
│   ├── __init__.pyc
│   ├── routes
│   │   ├── __init__.py
│   │   ├── __init__.pyc
│   │   ├── home_routes.py
│   │   └── home_routes.pyc
│   ├── static
│   │   └── css
│   │       ├── main.css
│   │       └── main2.css
│   └── templates
│       └── main.html
├── app.yaml
├── appengine_config.py
├── appengine_config.pyc

4个目录，9个文件

Answer 1

这似乎是flask-assets和Google App Engine的一个问题，因为GAE不允许在运行时创建文件。

可能的重复项：GAE: Flask/webassets throws an expection on {% extends "base.html" %}

要么在部署到GAE之前缩小css，要么在运行时(不首选)或构建时(首选)找到一种不同的方法来服务缩小的css。

一种可能性是在第一次运行(buildtime)时创建精简的js，然后可以将其上传到google存储桶中。

另一种选择是在运行时创建精简的js，并将其存储在memcache中。