MDBOOK010 - Preprocessor Validation

Missing or invalid preprocessor configuration.

Why This Rule Exists

mdBook preprocessors transform content before rendering. Using preprocessor directives without proper configuration causes silent failures or build errors.

Examples

Incorrect

Using a directive without configuring the preprocessor:

{{#katex}}
E = mc^2
\{{/katex}}

Without [preprocessor.katex] in book.toml.

Correct

First, configure in book.toml:

[preprocessor.katex]

Then use the directive:

{{#katex}}
E = mc^2
\{{/katex}}

Common Preprocessors

Preprocessor	Purpose
`katex`	Math equations
`mermaid`	Diagrams
`toc`	Table of contents
`template`	Template expansion
`admonish`	Callout boxes

Configuration

This rule has no configuration options.

Rule Details

Rule ID: MDBOOK010
Aliases: preprocessor-validation
Category: MdBook
Severity: Warning
Stability: Experimental
Auto-fix: No

MDBOOK011 - Template validation

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