TemplateDoesNotExist在python app-engine django 1.2上,同时模板渲染相对路径

Question

我在Windows机器上本地运行1.4.2 appengine SDK.我有一个运行Django 0.96的应用程序.模板渲染使用的是django包装器

google.appengine.ext.webapp.template.render

渲染模板.我经常使用相对路径来链接我的模板,例如

{% extends "../templates/base.html" %}

升级到Django 1.2之后,appengine的Django 1.2 lib文件夹中的django.template.loader中的find_template方法现在在使用相对路径时引发TemplateDoesNotExist

for loader in template_source_loaders:
    try:
        #raises TemplateDoesNotExist name='../templates/home.html' dirs=None
        source, display_name = loader(name, dirs)
        return (source, make_origin(display_name, loader, name, dirs))
    except TemplateDoesNotExist:
        pass
raise TemplateDoesNotExist(name)

我已经一直在单步执行Django和AppEngine代码,但看不出任何理由.任何人都可以提供更多见解吗？

谢谢,

理查德

Answer 1

当我从0.96转换为1.2 Django模板时,这个问题也让我感到困惑.当SDK 1.4.2开始发出我需要选择版本的警告时,我最初被推动这样做,但是当我查看模板语言中急需的改进时,我急于做出改变.

然后一切都破了.和你一样,我在我extends和include命令中使用了很多相对路径.它花了很多调试和挖掘,但我确实找出了问题的原因和一个非常好的解决方案.

原因:在Django 1.2中,加载模板文件的代码开始使用一个命令safe_join来连接路径部分(你可以看到代码google_appengine\lib\django_1_2\django\template\loaders\filesystem.py).它不允许相对路径超出它认为的顶级目录.这与配置为阻止您通过将某些内容粘贴..到URL中来访问服务器的整个文件系统的Web服务器相同.最终的结果是

{% extends "../templates/base.html" %}

曾经很好的打破规则,它不会起作用.

我在我的应用程序中修复此问题而不完全重构模板的方式是通过实现自定义TemplateLoader.Django的模板渲染引擎允许应用程序拥有许多不同的类,这些类知道如何以不同的方式查找模板.如果你查看我上面给出的目录,你会看到提供了几个,它们都是从BaseLoader继承的类.我提供了自己的定制,我的模板是如何布局的.

我的项目有类似Rails的布局:

app/
   controllers/
      home_controller.py
      posts_controller.py
   models/
      ...
   views/
      home/
          index.html
          about.html
      posts/
          show.html
          new.html
      shared/
          base.html
          post.html

每个模板都扩展base.html,一对包括post.html,他们以前使用相对路径到达他们的位置base/.理想情况下,我甚至不想使用..up-dir到达那里,但它需要0.96.我创建了以下模板加载器来使用我的方案:

from django.conf import settings
from django.template import TemplateDoesNotExist
from django.template.loader import BaseLoader
from django.utils._os import safe_join
import os

class MvcTemplateLoader(BaseLoader):
    "A custom template loader for the MVCEngine framework."

    is_usable = True

    __view_paths = None

    def __init__(self, views_path):
        self.views_path = views_path
        # We only need to instantiate the view_paths class variable once.
        if MvcTemplateLoader.__view_paths is None:
            temp_paths = []
            for each_path in os.listdir(views_path):
                # We want to skip hidden directories, so avoid anything that starts with .
                # This works on both Windows and *NIX, but could it fail for other OS's?
                if not each_path.startswith('.'):
                    full_path = os.path.join(views_path, each_path)
                    if each_path == "shared":
                        # The shared directory is special. Since templates in many other directories will be
                        # inheriting from or including templates there, it should come second, right after the
                        # root views directory. For now, it will be first.
                        temp_paths.insert(0, full_path)
                    else:
                        temp_paths.append(full_path)
            # The root views_path itself will always be first in order to give resolution precendence to templates
            # that are specified with a parent directory. In other words, home/index.html will be immediately
            # resolved with no ambiguity; whereas, index.html could resolve as bar/index.html rather than
            # foo/index.html.
            temp_paths.insert(0, views_path)
            MvcTemplateLoader.__view_paths = temp_paths


    def get_template_sources(self, template_name):
        for template_dir in MvcTemplateLoader.__view_paths:
            try:
                yield safe_join(template_dir, template_name)
            except UnicodeDecodeError:
                # The template dir name was a bytestring that wasn't valid UTF-8.
                raise
            except ValueError:
                # The joined path was located outside of this particular
                # template_dir (it might be inside another one, so this isn't
                # fatal).
                pass

    def load_template_source(self, template_name, template_dirs=None):
        tried = []
        for filepath in self.get_template_sources(template_name):
            try:
                file = open(filepath)
                try:
                    return (file.read().decode(settings.FILE_CHARSET), filepath)
                finally:
                    file.close()
            except IOError:
                tried.append(filepath)

        error_msg = "Could not find %s in any of the views subdirectories." % template_name
        raise TemplateDoesNotExist(error_msg)
    load_template_source.is_usable = True

_loader = MvcTemplateLoader

我使我的自定义模板加载器包含在Django尝试的集合中,通过将我的应用程序的main功能更改为如下所示:

def main():    
    from google.appengine.dist import use_library
    use_library('django', '1.2')

    os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'

    from django.conf import settings 
    views_path = os.path.join(os.path.dirname(__file__), 'app','views')
    settings.TEMPLATE_LOADERS = (('gaemvclib.mvctemplateloader.MvcTemplateLoader', views_path), 'django.template.loaders.filesystem.Loader', 'django.template.loaders.app_directories.Loader')

(然后通常进入你的主要功能的所有其他东西).

所以,我认为你应该能够修改上面的TemplateLoader代码以符合您如何你的模板目录摆出来,它会给你不仅在更大的控制你如何布置你模板hierarcy而且你如何编写extends和include声明.您不再使用..,而是仅仅提供模板的路径相对于项目中的任何内容相当于我的views目录.