Error with custom_fences fence_mermaid_custom function

[GeneralZero]

I am trying to build my documentation with mkdocs. And keep running in to this error.

Looking into the plugin.py script the _activate_custom_loader function doesn't exist.

DEBUG   -  Building page Mobile/Android/Safety Net.md
DEBUG   -  Running `page_context` event from plugin 'material/search'
DEBUG   -  Running `post_page` event from plugin 'mermaid2'
INFO    -  MERMAID2  - Found superfences config: {'preserve_tabs': True, 'custom_fences': [{'name': 'math', 'class': 'arithmatex', 'format': functools.partial(<function _fence_generic_format at 0x7bc1f9c11c60>, tag='div')}, {'name': 'latex', 'class': 'arithmatex', 'format': functools.partial(<function _fence_generic_format at 0x7bc1f9c11c60>, tag='div'), 'kwds': {'mode': 'generic', 'tag': 'pre'}}, {'name': 'mermaid', 'class': 'mermaid', 'format': functools.partial(<function fence_mermaid at 0x7bc1f99d72e0>, custom=True)}, {'name': 'tree', 'class': 'tree', 'format': <function fence_div_format at 0x7bc1f99e4400>}, {'name': 'ghostscript', 'class': 'tree', 'format': <function fence_div_format at 0x7bc1f99e4400>}, {'name': 'table', 'class': 'table', 'format': <function fence_table_format at 0x7bc1f99e6160>}]}
ERROR   -  Error building page 'Mobile/Android/Safety Net.md': 'functools.partial' object has no attribute '__name__'
Traceback (most recent call last):
  File "/usr/local/lib/python3.13/site-packages/mermaid2/plugin.py", line 159, in activate_custom_loader
    return self._activate_custom_loader
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'MarkdownMermaidPlugin' object has no attribute '_activate_custom_loader'. Did you mean: 'activate_custom_loader'?

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/mkdocs", line 8, in <module>
    sys.exit(cli())
             ~~~^^
  File "/usr/local/lib/python3.13/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.13/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/usr/local/lib/python3.13/site-packages/mkdocs/__main__.py", line 288, in build_command
    build.build(cfg, dirty=not clean)
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/mkdocs/commands/build.py", line 337, in build
    _build_page(
    ~~~~~~~~~~~^
        file.page, config, doc_files, nav, env, dirty, excluded=file.inclusion.is_excluded()
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/local/lib/python3.13/site-packages/mkdocs/commands/build.py", line 226, in _build_page
    output = config.plugins.on_post_page(output, page=page, config=config)
  File "/usr/local/lib/python3.13/site-packages/mkdocs/plugins.py", line 646, in on_post_page
    return self.run_event('post_page', output, page=page, config=config)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/mkdocs/plugins.py", line 566, in run_event
    result = method(item, **kwargs)
  File "/usr/local/lib/python3.13/site-packages/mermaid2/plugin.py", line 233, in on_post_page
    if self.activate_custom_loader:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/mermaid2/plugin.py", line 181, in activate_custom_loader
    if format_fn.__name__ == CUSTOM_FENCE_FN:
       ^^^^^^^^^^^^^^^^^^
AttributeError: 'functools.partial' object has no attribute '__name__'. Did you mean: '__ne__'?
The command '/bin/sh -c PYTHONPATH=/opt/MemoryViewer mkdocs build -v' returned a non-zero code: 1

[github-actions]

Thank you for your contribution! This is very appreciated.

[fralau]

Thanks.

It's perfectly expected that it raises an AttributeError on line 159, on first execution. What's odd is that the except clause doesn't catch it and I can't find fault with the code. 🤔

It might be a side effect of something else? Any specificity on your installation?

It would be useful to have minimal reproducible example (complete with mkdocs.yml).

mkdocs-mermaid2-plugin/mermaid2/plugin.py

Lines 149 to 171 in 0511d01

	@property
	def activate_custom_loader(self) -> bool:
	"""
	Predicate: activate the custom loader for superfences?
	The rule is to activate:
	1. superfences extension is activated
	2. it specifies 'fence_mermaid_custom' as
	as format function (instead of fence_mermaid)
	"""
	try:
	return self._activate_custom_loader
	except AttributeError:
	# first call:
	# superfences_installed = ('pymdownx.superfences' in
	# self.full_config['markdown_extensions'])
	# custom_loader = self.config['custom_loader']
	# self._activate_custom_loader = (superfences_installed and
	# custom_loader)
	# return self._activate_custom_loader
	self._activate_custom_loader = False
	superfences_installed = (SUPERFENCES_EXTENSION in
	self.full_config['markdown_extensions'])
	if superfences_installed:

[GeneralZero]

So while trying to make a minimal reproducible example it seems to have fixed itself. The only thing that I changed is purging the docker cache. So that was my solution in case someone runs into the same problem in the future.

[fralau]

Thanks for the info! I labelled this issue "useful tip" to keep track of it.

[mbeacom]

@fralau

Encountering the same error while running using the docker workflow with podman.

Dockerfile/Containerfile:

FROM squidfunk/mkdocs-material:9

RUN pip install --no-cache-dir mkdocs-mermaid2-plugin

fairly minimal mkdocs.yml

site_name: "Test Site"
site_description: "A test site."
site_author: "Test author"

theme:
  name: "material"
  features:
    - search.suggest
    - search.highlight
    - search.share
    - navigation.tracking
    - navigation.tabs
    - navigation.path
    - toc.integrate
    - toc.follow

markdown_extensions:
  - toc
  - footnotes
  - codehilite
  - admonition
  - def_list
  - pymdownx.superfences:
      custom_fences:
        - name: mermaid
          class: mermaid
          format: !!python/name:mermaid2.fence_mermaid_custom
          
plugins:
  - search
  - mermaid2

mermaid diagram example

# Model

```mermaid
erDiagram
  THING {
    string id PK
    string thingyId
    string[] stuffs
  }

  THINGY {
    string id PK
    string[] stuffys
  }

  THINGY ||--o{ THING : owns
```

[fralau]

Thanks. Still having the same error at mermaid2/plugin.py, line 159?

[GeneralZero]

Yep now its back and clearing the cache didn't work. So don't know exactly what is happening.

[GeneralZero]

I think I narrowed it down. Here is my minimum build yaml and the markdown file mermaid2 block. It seems to interact with another superfences plugin pymdownx.arithmatex.

mkdocs.yaml:

site_name: Memory
site_description: Notes I've collected over the years
site_author: GeneralZero

docs_dir: /opt/MemoryViewer/memory

theme:
  name: material
dev_addr: '127.0.0.1:8000'

repo_url: https://github.com/generalzero/
repo_name: Github

use_directory_urls: true

plugins:
  - mermaid2:
      arguments:
         theme: 'dark'


  - pymdownx.superfences:
      preserve_tabs: true
      custom_fences:
        - name: math
          class: arithmatex
          format: !!python/object/apply:pymdownx.arithmatex.arithmatex_fenced_format {which: "generic"}
        - name: latex
          class: arithmatex
          format: !!python/object/apply:pymdownx.arithmatex.arithmatex_fenced_format {which: "generic"}
        - name: mermaid
          class: mermaid
          format: !!python/name:mermaid2.fence_mermaid_custom #fence_mermaid_custom

sequenceDiagram
Client App ->> Google Play Services : SafetyNet Attestation API receives a call from your app. This call includes a nonce.
Google Play Services ->> Google : SafetyNet Attestation service evaluates the runtime environment and requests a signed attestation of the assessment results from Google's servers.
Google ->> Google Play Services : Google's servers send the signed attestation to the SafetyNet Attestation service on the device.
Google Play Services ->> Client App : SafetyNet Attestation service returns this signed attestation to your app.
Client App ->> Client Server : Your app forwards the signed attestation to your server.
Client Server ->> Client App : This server validates the response and uses it for anti-abuse decisions. Your server communicates its findings to your app.

Loading