Issue 5044 - Support absolute paths for Jinja templates

sitescripts/utils.py

 # This file is part of the Adblock Plus web scripts,
 # Copyright (C) 2006-2017 eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
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 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ skipping 128 matching lines @@
     try:
         return email.encode('ascii')
     except UnicodeEncodeError:
         return '%s@%s' % (match.group(1).encode('ascii'),
                           match.group(2).encode('idna'))
 
 _template_cache = {}
 
 
 def get_template(template, autoescape=True, template_path=siteScriptsPath):
-    """Parses and returns a Jinja2 template"""
-    key = (template_path, template, autoescape)
-    if not key in _template_cache:
+    """Load Jinja2 template.
+
+    If `template` is a relative path, it's looked up inside `template_path`.
+    If it's an absolute path, `template_path` is not used.
+
+    Note: Each template will only be loaded once (when first requested). After
+    that it will be cached and reused -- any changes on the filesystem will be
+    ignored.
+    """
+    if os.path.isabs(template):
+        template_path, template = os.path.split(template)
+    canonical_path = os.path.abspath(os.path.join(template_path, template))
+    key = (canonical_path, autoescape)

[Sebastian Noack, 2017/03/31 06:33:42]

Note that following are NOT equivalent:

  get_template('bar/baz.tmpl', template_path='/foo')
  get_template('baz.tmpl', template_path='/foo/bar')

If baz.tmpl is extending or including another template, the former will expect
to find the other template in '/foo', the latter in '/foo/bar'. So the key
should rather be constructed like that, which seems slightly simpler anyway:

  key = (template_path, template, autoescape)

[Vasily Kuznetsov, 2017/03/31 16:01:48]

Since it's not possible to escape Jinja template environment, the only way this
scenario could occur is if template environment B is located inside template
environment A and there's a template that lives in B and works correctly in both
producing different results (because of different includes and/or dependencies).
This seems pretty unlikely (although not impossible), so I understood Wladimir's
comment to mean "the key should just be the canonical path to the template
file". I suppose what he was actually suggesting was to canonicalize the content
of `template_path` variable. I have now done that.

+    if key not in _template_cache:
         if autoescape:
             env = get_template_environment(template_path)
         else:
             env = get_unescaped_template_environment(template_path)
         _template_cache[key] = env.get_template(template)
     return _template_cache[key]
 
 
 @cached(float('inf'))
 def get_template_environment(template_path):
@@ skipping 26 matching lines @@
       Returns a custom Jinja2 template environment with additional filters.
     """
     from sitescripts.templateFilters import filters
     import jinja2
     if not loader:
         loader = jinja2.FileSystemLoader(siteScriptsPath)
     env = jinja2.Environment(loader=loader, autoescape=True)
     env.filters.update(filters)
     env.filters.update(additional_filters)
     return env