ERROR - unexpected error: SuperFencesCodeExtension.extend_super_fences() missing 1 required positional argument: 'reset

[johnpiers]

I ran an "update" (uv pip install --upgrade mkdocs-materialx) and it updated - pymdown-extensions==12.0.1 to + pymdown-extensions==12.1 and on restarting the server, got few hundred of these:

ERROR - unexpected error: SuperFencesCodeExtension.extend_super_fences() missing 1 required positional argument: 'reset'

To fix it I just reverted the change back to "12.0.1"

Clarification on the root cause:

The mkdocs-markmap plugin isn't bundled directly into this (MaterialX) theme's core repository.

The error occurs for users who have installed mkdocs-markmap in their local setups alongside mkdocs-materialx. The mkdocs-markmap extension hooks into pymdownx.superfences, which breaks globally on every page when pymdown-extensions automatically updates to v12.1+ due to a required 4th positional argument (reset) missing from the plugin's code.

Leaving this note here for anyone else using this (MaterialX) theme boilerplate who hits the same server crash—pinning pymdown-extensions==12.0.1 locally safely bypasses the issue until the markmap plugin gets an update.

[johnpiers]

Root cause, more precisely: pymdown-extensions 12.1 changed SuperFencesCodeExtension.extend_super_fences() to require a 4th positional argument, reset (a callback for clearing any state a custom fence type holds between renders — 12.1 defaults to a no-op, default_reset, for its own built-in custom fences when nothing else is given). extension.py here only ever calls it with 3 arguments, which is what throws on 12.1+.

A version-tolerant fix, tested against both 12.0.1 and 12.1:

try:
    from pymdownx.superfences import default_validator, fence_code_format, _formatter, _validator
    try:
        # pymdown-extensions 12.1+ requires a 4th 'reset' argument
        from pymdownx.superfences import _reset, default_reset
        extension.extend_super_fences(
            "markmap",
            partial(_formatter, class_name="language-markmap", _fmt=fence_code_format),
            partial(_validator, validator=default_validator),
            partial(_reset, _reset=default_reset)
        )
    except ImportError:
        # pymdown-extensions < 12.1 has no 'reset' argument
        extension.extend_super_fences(
            "markmap",
            partial(_formatter, class_name="language-markmap", _fmt=fence_code_format),
            partial(_validator, validator=default_validator)
        )
    break

except ImportError as e:
    log.warning(f"markmap detected pymdownx.superfences, but import is not working: {e}")

This works on both 12.0.1 and 12.1+, so no pinning is needed once it's in.
Happy to open a PR if that's useful.