eslint-plugin-markdown-preferences

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markdown-preferences/atx-heading-closing-sequence-length ​

enforce consistent length for the closing sequence (trailing #s) in ATX headings.

  • ⚙️ This rule is included in plugin.configs.standard.
  • 🔧 The --fix option on the command line can automatically fix some of the problems reported by this rule.

📖 Rule Details ​

Enforces a consistent length for the closing sequence (trailing #s) in ATX headings (Markdown headings that start with #). This rule does not enforce whether a closing sequence is present or absent. If a closing sequence exists, its length is checked. If the length is incorrect, the number of trailing #s is automatically adjusted by inserting or removing #s as needed. The closing sequence is never removed entirely, and headings without a closing sequence are ignored by this rule. Setext headings (those using === or ---), and headings that consist only of # with no text, are also ignored.

Mode: closing sequence length matches heading level ("match-opening")

md
<!-- eslint markdown-preferences/atx-heading-closing-sequence-length: ["error", {"mode": "match-opening"}] -->
<!-- ✓ GOOD (with { "mode": "match-opening" }) -->
# Heading #
## Heading ##
<!-- ✗ BAD (with { "mode": "match-opening" }) -->
# Heading 
###

## Heading 
#

Mode: closing sequence length is always 2 ({ "mode": "length", "length": 2 })

md
<!-- eslint markdown-preferences/atx-heading-closing-sequence-length: ["error", {"mode": "length", "length": 2}] -->
<!-- ✓ GOOD (with { "mode": "length", "length": 2 }) -->
# Heading ##
## Heading ##
<!-- ✗ BAD (with { "mode": "length", "length": 2 }) -->
# Heading 
#

## Heading 
###

Mode: all headings have a total line length of 30 ({ "mode": "fixed-line-length", "length": 30 })

md
<!-- eslint markdown-preferences/atx-heading-closing-sequence-length: ["error", {"mode": "fixed-line-length", "length": 30}] -->
<!-- ✓ GOOD (with { "mode": "fixed-line-length", "length": 30 }) -->
# Short heading ##############
## Long heading ##############
<!-- ✗ BAD (with { "mode": "fixed-line-length", "length": 30 }) -->
# Short heading 
#

## Long heading 
###

Mode: all headings have the same number of trailing # as the first heading with a closing sequence ("consistent")

md
<!-- eslint markdown-preferences/atx-heading-closing-sequence-length: ["error", {"mode": "consistent"}] -->
<!-- ✓ GOOD (with { "mode": "consistent" }) -->
# Heading #
## Heading #
<!-- ✗ BAD (with { "mode": "consistent" }) -->
# Heading #
## Heading 
##

Mode: all headings are padded with trailing # so that each heading line has the same length as the shortest line that can fully contain the longest heading in the document ("consistent-line-length")

md
<!-- eslint markdown-preferences/atx-heading-closing-sequence-length: ["error", {"mode": "consistent-line-length"}] -->
<!-- ✓ GOOD (with { "mode": "consistent-line-length" }) -->
# Short ##########
## Long heading ##
<!-- ✗ BAD (with { "mode": "consistent-line-length" }) -->
# Short 
#

## Long heading 
###

🔧 Options ​

json
{
  "markdown-preferences/atx-heading-closing-sequence-length": [
    "error",
    {
      "mode": "match-opening",
      "length": null
    }
  ]
}

This rule accepts an object option with the following properties:

  • mode (required):
    • "match-opening" (default): The number of trailing #s must match the number of leading #s (the heading level).
    • "length": All ATX headings must have the specified number of trailing #s. Requires the length property.
    • "consistent": All ATX headings in the document must have the same number of trailing # as the first ATX heading with a closing sequence.
    • "consistent-line-length": All ATX headings must be padded with trailing # so that each heading line has the same length as the shortest line that can fully contain the longest heading in the document.
    • "fixed-line-length": All ATX headings must have the specified total line length, by padding with trailing # as needed. Requires the length property.
  • length (number, required for "length" and "fixed-line-length"): The required length for the closing sequence or the total line length.

📚 Further Reading ​

🚀 Version ​

This rule was introduced in eslint-plugin-markdown-preferences v0.13.0

🔍 Implementation ​