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    MDS042 prose ready

    MDS042: emphasis-style

    Enforces a single delimiter character for bold and italic emphasis, and optionally forbids cross-delimiter nesting.

    CommonMark accepts **bold**, __bold__, *italic*, and _italic_ interchangeably. Mixed delimiters produce inconsistent diffs. This rule makes the choice explicit.

    # Settings

    KeyTypeDefaultDescription
    boldstring""Required delimiter: asterisk or underscore.
    italicstring""Required delimiter: asterisk or underscore.
    forbid-mixed-nestingboolfalseFlag emphasis whose delimiter differs from its parent emphasis.

    Leave bold or italic empty to skip enforcement for that role.

    # Config

    rules:
  emphasis-style:
    bold: asterisk
    italic: underscore
    forbid-mixed-nesting: true

    Disable (default):

    rules:
  emphasis-style: false

    # Diagnostics

    bold uses underscore; configured style is asterisk
italic uses asterisk; configured style is underscore
mixed emphasis delimiters: underscore wraps asterisk

    # Examples

    # Good

    # Heading

Some **bold** and _italic_ text.

    # Bad

    # Heading

Some __bold__ text.

    # Auto-fix

    Opening and closing delimiter bytes are replaced in the source. The fix is byte-for-byte substitution.

    The following cases emit diagnostics but are not auto-fixed:

    • Triple-delimiter runs such as ***x*** — the nesting boundary is ambiguous.
    • Emphasis with a non-text first child (e.g. **[link](url)**) — the opening delimiter position cannot be determined reliably; no diagnostic is emitted either, so these are silently skipped.
    • Emphasis with a non-text last child (e.g. **text [link](url)**) — the closing delimiter position cannot be determined. A diagnostic is still reported; only the fix is suppressed.
    • forbid-mixed-nesting only — when neither bold nor italic is configured, mixed-nesting diagnostics are emitted but the rule has no replacement delimiter to apply, so fix leaves those diagnostics unchanged.

    # Meta-Information

    View source on GitHub