Jinja2 errors after upgrading to 9.6.10 with pip

[johnnovak]

Context

Update: Upgrading to the latest Jinja2 3.1.6 manually resolved the issue. I was on 3.0.3 and upgrading to the latest mkdocs material version did not cause Jinja2 to upgrade.

Someone apparently is trying to fix it here:
#8132

Bug description

I'm a long-time mkdocs material users. I've done a pip install mkdocs-material this morning to upgrade, which went fine, but I'm no longer able to use it as it keeps failing with a Jinja 2 error.

I've uninstalled then reinstalled mkdocs-material, but it didn't help.

mkdocs itself works; it's apparently the templates in mkdocs material that isn't compatible with a more recent version of jinja2 or something.

This is the error I'm getting:

INFO    -  Building documentation...
INFO    -  Cleaning site directory
Traceback (most recent call last):
  File "/home/jnovak/.local/bin/mkdocs", line 8, in <module>
    sys.exit(cli())
  File "/home/jnovak/.local/lib/python3.10/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/home/jnovak/.local/lib/python3.10/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/home/jnovak/.local/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/jnovak/.local/lib/python3.10/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/jnovak/.local/lib/python3.10/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/__main__.py", line 272, in serve_command
    serve.serve(**kwargs)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/commands/serve.py", line 85, in serve
    builder(config)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/commands/serve.py", line 67, in builder
    build(config, serve_url=None if is_clean else serve_url, dirty=is_dirty)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/commands/build.py", line 328, in build
    _build_theme_template(template, env, files, config, nav)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/commands/build.py", line 103, in _build_theme_template
    output = _build_template(template_name, template, files, config, nav)
  File "/home/jnovak/.local/lib/python3.10/site-packages/mkdocs/commands/build.py", line 83, in _build_template
    output = template.render(context)
  File "/usr/lib/python3/dist-packages/jinja2/environment.py", line 1291, in render
    self.environment.handle_exception()
  File "/usr/lib/python3/dist-packages/jinja2/environment.py", line 925, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/home/jnovak/.local/lib/python3.10/site-packages/material/templates/404.html", line 4, in top-level template code
    {% extends "main.html" %}
  File "/home/jnovak/.local/lib/python3.10/site-packages/material/templates/main.html", line 4, in top-level template code
    {% extends "base.html" %}
  File "/usr/lib/python3/dist-packages/jinja2/environment.py", line 925, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/home/jnovak/.local/lib/python3.10/site-packages/material/templates/base.html", line 80, in template
    <meta {% for key, value in tag | items %} {{ key }}="{{value}}" {% endfor %}>
jinja2.exceptions.TemplateAssertionError: No filter named 'items'.

Related links

N/A

Reproduction

Skipping this step as the problem is reproducible with the minimal website from the tutorial.

Steps to reproduce

1. Create a new mkdocs site with mkdocs new
2. Set up a basic mkdocs material site (from the tutorial):

site_name: My Docs
site_url: https://mydomain.org/mysite
theme:
  name: material

3. Execute either mkdocs server or mkdocs build.

Browser

Firefox

Before submitting

• I have read and followed the bug reporting guidelines.
• I have attached links to the documentation, and possibly related issues and discussions.
• I assure that I have removed all customizations before submitting this bug report.
• I have attached a .zip file with a minimal reproduction using the built-in info plugin.

[squidfunk]

Fixed by merging #8132 by @blumbra63.

[squidfunk]

Released as part of 9.6.11.