The concept of "output encoding" is not described anywhere

[Mingun]

Currently a paragraph about it gives no idea what is "output encoding" and why it is needed:

encoding/encoding.bs

Lines 733 to 746 in 4f549cd

	<h3 id=output-encodings>Output encodings</h3>
	<p>To <dfn export>get an output encoding</dfn> from an <a for=/>encoding</a>
	<var>encoding</var>, run these steps:
	<ol>
	<li><p>If <var>encoding</var> is <a>replacement</a> or <a>UTF-16BE/LE</a>, then return
	<a>UTF-8</a>.
	<li><p>Return <var>encoding</var>.
	</ol>
	<p class=note>The <a>get an output encoding</a> algorithm is useful for URL parsing and HTML
	form submission, which both need exactly this.

It would be good to describe what it is, what problems it solves and where you should use it.

[annevk]

Doesn't the note address that?

[Mingun]

I think no. At least for me it is still unclear. For example, percent-decoding algorithm is also useful for URL parsing, but that does not explain, why URL can be percent-encoded.

[annevk]

The respective encodings don't have a defined encoder and the reason these older features use legacy encodings to encode is mainly an accident of history. I suppose I'd support an amendment of the note to that effect.

[Mingun]

The respective encodings don't have a defined encoder

Well, that's a recursive explanation. Why they don't have a defined encoder? Why did someone decide that if we could not encode the text in one encoding, then some other would be suitable for us? It looks absurd! I.e. we tell the recipient that we have one encoding and are actually encoded into another. Or we definitely know that the consumer expects one specific encoding, we try to encode into it... and get a text encoded in other encoding instead of error explaining that this encoding is unsupported. I have no idea what scenario of use such a substitution has. Can this be explained in the specification together with examples when this can be needed?

[annevk]

That's a different question though and would better be addressed elsewhere. The answer is that none is needed for the web.