Empty destinations in link references

[mildsunrise]

Since <> is a valid link destination, a link reference should be able to have <> as the destination.

So I suggest to add the following test in link references:

.
[foo]: <>

[foo]
.
<p><a href="">foo</a></p>
.

May result obvious but some parsers (including the JS implementation) fail.

[jgm]

Removing the test for an empty URL in js/lib/inlines.js, line 362, fixes the js implementation for this test, but causes it to fail the test:

.
[foo]:

[foo]
.
<p>[foo]:</p>
<p>[foo]</p>
.

I wonder, though: shouldn't we allow this kind of thing too as a way of specifying an empty link?

[mildsunrise]

Yeah, we could allow it for more consistency with inline links.

[rlidwka]

[foo]: <> looks like an empty link indeed, but [foo]: should not be parsed as a reference imho.

[Knagis]

In my opinion the question that should be answered is "Are empty links allowed in the references and inline links?".

If the answer is yes, then both [foo]:<> and [foo]: should be recognized as valid and empty links to reduce further surprises.

I don't see how [foo]: could be present in a document on its own line but the writer intended it to mean anything else... Although... Maybe something like this where this sort-of reference is followed by a list:

[horse]: http://wiki/horse
[animals]:
1. [horse];
2. [cat];

[animals]: http://wiki/animals

Babelmark2

[jgm]

I once had the thought that an empty reference definition could be given a special meaning as an anchor, as illustrated by the following (which would have been really handy in spec.txt):

[link text]:

The link text cannot contain links, though it may
contain images.  Etc.

... later ...

See the discussion of [link text], above.

where this gets converted to:

<a id="link-text"></a>

<p>The link text cannot contain links, though it may
contain images.  Etc.</p>

... later ...

<p>See the discussion of <a href="#link-text">link text</a>, above.</p>

I think it was that thought that made me hesitate about interpreting empty link definitions as defining regular links to empty URLs.

[mildsunrise]

I love the idea!

[rlidwka]

Yep, same here. Links to the same document frequently appear in readme's for example, it'd be nice to avoid putting html tags there.

[jgm]

Discussion here: http://talk.commonmark.org/t/turning-empty-link-definitions-into-anchors/893