Rule - MD049

Property	Value
Aliases	md049, emphasis-style
Autofix Available	Pending
Enabled By Default	Yes

Summary

Ensure consistent emphasis style across the document.

Reasoning

Readability

To maintain a uniform appearance and improve readability, the character sequence used for inline emphasis (e.g., asterisks vs. underscores) should remain consistent throughout a document or set of documents.

Examples

Failure Scenarios

This rule triggers when the document mixes asterisks (*) and underscores (_) for inline emphasis under the default consistent style.

This is *one* emphasis.

This is _another_ emphasis.

Explanation: This example fails because the first line uses asterisks (*) for emphasis while the second line uses underscores (_). With the default consistent style, the first emphasis block sets the expected style to asterisks. The subsequent use of underscores violates this consistency requirement.

Unlike the previous example, which relies on the default consistent style, this scenario violates the rule when the style configuration is explicitly set to asterisk. All emphasis blocks use underscores, but underscores are not permitted in this strict mode.

This is _one_ emphasis.

This is _another_ emphasis.

Explanation: This example fails because the configuration style is set to asterisk, which mandates that only asterisks (*) may be used for emphasis. Although both blocks use underscores consistently, underscores are prohibited in this mode.

Unlike the previous example, which demonstrated a violation of the asterisk configuration, this scenario violates the rule when the style configuration is explicitly set to underscore. Even if all emphasis blocks use asterisks consistently among themselves, they fail the rule because asterisks are not permitted in this strict mode.

This is *one* emphasis.

This is *another* emphasis.

Explanation: This example fails because the style configuration is set to underscore, which mandates that only underscores (_) may be used for emphasis. Although both blocks use asterisks consistently, asterisks are prohibited in this mode.

Correct Scenarios

This rule does not trigger when all inline emphasis blocks use the same delimiter character under the default consistent style.

This is *one* emphasis.

This is the *same* emphasis.

Explanation: This example passes because both emphasis blocks use asterisks (*). This is consistent with the default consistent style, which adopts the style of the first emphasis block encountered.

Unlike the previous example, which relied on the default consistent style, this scenario demonstrates compliance when the style configuration is explicitly set to underscore. All emphasis blocks use underscores, satisfying the strict configuration requirement.

This is _one_ emphasis.

This is _another_ emphasis.

Explanation: This example passes because the configuration style is set to underscore, which mandates that only underscores (_) may be used for emphasis. Both blocks use underscores, satisfying this requirement.

Unlike the previous example, which satisfied the underscore style, this scenario demonstrates compliance when the style configuration is explicitly set to asterisk. All emphasis blocks use asterisks, satisfying the strict configuration requirement.

This is *one* emphasis.

This is *another* emphasis.

Explanation: This example passes because the configuration style is set to asterisk, which mandates that only asterisks (*) may be used for emphasis. Both blocks use asterisks, satisfying this requirement.

Fix Description

The implementation for this feature is tracked with this issue.

Configuration

Prefixes
plugins.md049.
plugins.emphasis-style.

Value Name	Type	Default	Description
enabled	boolean	True	Whether the Rule Plugin is enabled.
style	string	consistent	Style of emphasis block characters expected in the document.

Valid Styles

Style	Description
consistent	The first emphasis block in the document specifies the style for the rest of the document.
asterisk	Only asterisks are to be used for inline emphasis block elements.
underscore	Only underscores are to be used for inline emphasis block elements.

Origination of Rule

This rule is largely inspired by the MarkdownLint rule MD049.