Struct MD001HeadingIncrement 

pub struct MD001HeadingIncrement;

Rule MD001: Heading levels should only increment by one level at a time

See docs/md001.md for full documentation, configuration, and examples.

This rule enforces a fundamental principle of document structure: heading levels should increase by exactly one level at a time to maintain a proper document hierarchy.

Purpose

Proper heading structure creates a logical document outline and improves:

• Readability for humans
• Accessibility for screen readers
• Navigation in rendered documents
• Automatic generation of tables of contents

Examples

Correct Heading Structure

# Heading 1
## Heading 2
### Heading 3
## Another Heading 2

Incorrect Heading Structure

# Heading 1
### Heading 3 (skips level 2)
#### Heading 4

Behavior

This rule:

• Tracks the heading level throughout the document
• Validates that each new heading is at most one level deeper than the previous heading
• Allows heading levels to decrease by any amount (e.g., going from ### to #)
• Works with both ATX (#) and Setext (underlined) heading styles

Fix Behavior

When applying automatic fixes, this rule:

• Changes the level of non-compliant headings to be one level deeper than the previous heading
• Preserves the original heading style (ATX or Setext)
• Maintains indentation and other formatting

Rationale

Skipping heading levels (e.g., from h1 to h3) can confuse readers and screen readers by creating gaps in the document structure. Consistent heading increments create a proper hierarchical outline essential for well-structured documents.

Trait Implementations

impl Clone for MD001HeadingIncrement

fn clone(&self) -> MD001HeadingIncrement

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MD001HeadingIncrement

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for MD001HeadingIncrement

fn default() -> MD001HeadingIncrement

Returns the “default value” for a type.

impl Rule for MD001HeadingIncrement

fn name(&self) -> &'static str

fn description(&self) -> &'static str

fn check(&self, ctx: &LintContext<'_>) -> LintResult

fn fix(&self, ctx: &LintContext<'_>) -> Result<String, LintError>

fn category(&self) -> RuleCategory

Get the category of this rule for selective processing

fn should_skip(&self, ctx: &LintContext<'_>) -> bool

Check if this rule should quickly skip processing based on content

fn as_any(&self) -> &dyn Any

fn as_maybe_document_structure(&self) -> Option<&dyn MaybeDocumentStructure>

fn from_config(_config: &Config) -> Box<dyn Rule>

where Self: Sized,

Factory: create a rule from config (if present), or use defaults.

fn check_with_structure( &self, ctx: &LintContext<'_>, _structure: &DocumentStructure, ) -> LintResult

Enhanced check method using document structure By default, calls the regular check method if not overridden

fn check_with_ast( &self, ctx: &LintContext<'_>, _ast: &MarkdownAst, ) -> LintResult

AST-based check method for rules that can benefit from shared AST parsing By default, calls the regular check method if not overridden

fn check_with_structure_and_ast( &self, ctx: &LintContext<'_>, _structure: &DocumentStructure, _ast: &MarkdownAst, ) -> LintResult

Combined check method using both document structure and AST By default, calls the regular check method if not overridden

fn uses_ast(&self) -> bool

Check if this rule can benefit from AST parsing

fn uses_document_structure(&self) -> bool

Check if this rule can benefit from document structure

fn as_maybe_ast(&self) -> Option<&dyn MaybeAst>

fn default_config_section(&self) -> Option<(String, Value)>

Returns the rule name and default config table if the rule has config. If a rule implements this, it MUST be defined on the impl Rule for ... block, not just the inherent impl.

fn config_aliases(&self) -> Option<HashMap<String, String>>

Returns config key aliases for this rule This allows rules to accept alternative config key names for backwards compatibility

fn fix_capability(&self) -> FixCapability

Declares the fix capability of this rule