Checks Markdown code blocks in a MkDocs site against user-defined actions

pip install mkdocs-code-validator

Activate the plugin in mkdocs.yml. The identifiers config is mandatory. And the plugin doesn't work without pymdownx.superfences:

plugins:
  - search
  - code-validator:
      identifiers:
        bash:
          validators:
            - grep a
markdown_extensions:
  - pymdownx.superfences

The above contrived config checks that every ```bash code block in the Markdown files of this MkDocs site must contain the letter "a", otherwise a warning will appear.

The content of each code block is piped as stdin to the command. The exit code of the command is what's checked: a non-zero code will produce a warning (which in MkDocs you can make fatal with the --strict flag). The output of the command is not used in any way, only preserved on the screen as part of a warning.

You can add any number of identifiers, and within them any number of validators commands, each of them has the ability to produce a warning.

If stdin is not usable with your command, the input can be passed as a temporary file instead -- that is done if the command contains the exact argument $< (which is then replaced with a file path). For the above example, changing the command to grep a $< would be equivalent (other than technicalities).

The commands do not allow freeform shell syntax, it's just one subprocess to call with its arguments. To explicitly opt into a shell, just run it as (e.g.) sh -c 'if grep a; then exit 1; fi'. Or, with a temporary file: sh -c 'if grep a "$1"; then exit 1; fi' $<.

The definition of what a code block is is all according to the pymdownx.superfences extension. It must be enabled; the plugin won't do anything without it.