[MD077] Use MkDocs indentation even in Commonmark documents

[skyzyx]

Problem or motivation

I use rumdl alongside editorconfig-checker, which is a tool that enforces that documents follow the .editorconfig configuration.

When applied to .md documents with indent = 2, this means that second lines must be indented 4 spaces, then 6, etc. My documents are GFM documents, and to pass the editorconfig-checker check, next lines must be 4 spaces. However MD077 instructs Commonmark documents to use 3 spaces. If it were an MkDocs document, it could be 4. But there does not seem to be a way to instruct rumdl to use 4 spaces intentionally.

This causes a conflict during the linting/fixing stage of my development pipeline with tools arguing with each other.

Proposed solution

• Let .editorconfig override what MD077 validates against.
• Allow Commonmark documents to use MkDocs indentation rules.
• Allow the user to somehow specify $2n$, $3n$, $4n$, …, etc., where $n$ is the indentation level.

Alternatives considered

Disable MD077.

Feature category

Improve existing rule

Example markdown

This is what is expected by rumdl with 2-space indentation and a second line for a Commonmark document.

* This is a sentence in a list item.

   This is a second sentence in a list item.

This is what I'd like to achieve as a valid configuration.

* This is a sentence in a list item.

    This is a second sentence in a list item.

Contribution

• I would be willing to submit a PR to implement this feature

Additional context

I haven't learned Rust yet. Sorry.

[rvben]

Implemented in v0.2.50, as an indent option on MD077:

[MD077]
indent = 4

With that set, the document you asked for is clean, and rumdl fmt produces it from the 3-space form:

$ rumdl check want.md
Success: No issues found in 1 file

The requirement is per item: the item's own marker column plus the configured indent. So a top-level item needs 4, and a nested item whose marker sits at column 2 needs 6, which is the shape you described. indent = 2 works the same way if you prefer the tighter form.

That also removes the collision you hit. Without the option the requirement follows each item's content column, which is 3 for 1. and 2 for * , so a document mixing the two produces both an odd and an even continuation and editorconfig-checker can only accept one of them. A configured indent makes every item agree.

On the .editorconfig route: rumdl does read .editorconfig when you set [global] editorconfig = true, but indent_size maps onto MD007's list indent, not MD077's continuation indent, so it would not have answered this. Even if it did, your indent_size = 2 would have chosen a 2-space continuation rather than the 4-space form in your example. The explicit key is what lets you say which one you want.

Thanks to @DavidPandleton, who implemented this in #786.

[skyzyx]

Thank you!