Allow html messages in keys ending with `.html`

[AdrianFahrbach]

Clear and concise description of the problem

Currently the only way to use HTML messages without warnings is to set warnHtmlInMessage to false. This removes the warning for all keys though.

Suggested solution

Keys ending with .html should be allowed to have HTML messages. That way the warning can be "disabled" only where it is needed. This also provides a hint to the developer when working with this key, that it contains HTML.

Alternative

No response

Additional context

No response

Validations

• Read the Contributing Guidelines
• Read the Documentation
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[kazupon]

Thank you for the suggestion!
Sorry late my reply

We understand the need for more granular control over HTML in translation messages. However, rather than adding a convention-based approach (.html suffix), we are planning to address this more fundamentally.

In v12, we will plan to introduce MF2 (MessageFormat 2) simple message support, which includes a markup syntax. With MF2 markup, you can express rich text in a structured and safe way without embedding raw HTML:

// MF2 markup syntax
{{Click {#bold}{$name}{/bold} to continue}}

The markup elements (e.g., {#bold}, {/bold}) are controlled by the renderer, not by the translation string itself. This provides several advantages over raw HTML in messages:

• No XSS risk — the parser controls markup, preventing arbitrary HTML injection
• warnHtmlMessage becomes unnecessary — structured markup replaces raw HTML strings
• Renderer-controlled output — the app decides how {#bold} maps to actual elements (e.g., <strong>, <b>, or a custom component)

We believe MF2 markup will be a better long-term solution for this use case. We'll keep this issue open for tracking, but the planned approach will be through MF2 support rather than a key-naming convention.