Additional parser test cases for delayed extends usage

We want it to be possible to turn a <ref> into an extended one after
it was re-used for the first time, not knowing if it later turns out
to be an extended ref.

This should work: <ref name=x/> is a short re-use of a ref that later
turns out to be a <ref extends=… name=x>…</ref>.

<ref name=x></ref> is just another syntax that should behave
identical.

However, it should probably not be possible to turn
<ref name=x>foo</ref> into a subref later because it really, really
looks like a normal ref. Even if the content matches with a later
<ref extends=… name=x>foo</ref> and we usually ignore identical
content, I suggest to block this with a dedicated error message. But
this is for a later patch. This patch here just documents the status
quo.

This patch also contains minor code cleanups that will be useful in
Ia752a7d.

Bug: T367749
Change-Id: Ie38769b36e5c476b96e7af7f03b0fc800b32ba97

src/Cite.php

@@ -174,9 +174,12 @@ class Cite {
 		// @phan-suppress-next-line PhanParamTooFewUnpack No good way to document it.
 		$ref = $this->referenceStack->pushRef(
 			$parser->getStripState(), $text, $argv, ...array_values( $arguments ) );
-		return $ref
+		if ( !$ref ) {
-			? $this->footnoteMarkFormatter->linkRef( $parser, $ref )
+			// Rare edge-cases like follow="…" don't render a footnote marker in-place
-			: '';
+			return '';
+		}
+
+		return $this->footnoteMarkFormatter->linkRef( $parser, $ref );
 	}
 
 	/**

tests/parser/bookReferencing.txt

@@ -129,6 +129,73 @@ wgCiteBookReferencing=true
 </p>
 !! end
 
+# TODO: T367749 - We are misusing an existing error message here that is super confusing
+!! test
+T367749 - Turning a top-level ref into a subref is forbidden, even if the content is the same
+!! config
+wgCiteBookReferencing=true
+!! wikitext
+<ref name=p20>page 20</ref>
+<ref extends=book name=p20>page 20</ref>
+<references>
+<ref name=book>book</ref>
+</references>
+!! html
+<p><sup id="cite_ref-p20_1-0" class="reference"><a href="#cite_note-p20-1">&#91;1&#93;</a></sup>
+<span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "p20" defined multiple times with different content</span>
+</p>
+<div class="mw-references-wrap"><ol class="references">
+<li id="cite_note-p20-1"><span class="mw-cite-backlink"><a href="#cite_ref-p20_1-0">↑</a></span> <span class="reference-text">page 20</span>
+</li>
+</ol></div>
+<p><span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: <code>&lt;ref&gt;</code> tag with name "book" defined in <code>&lt;references&gt;</code> is not used in prior text.</span>
+</p>
+!! end
+
+!! test
+T367749 - Turning a top-level ref into a subref is forbidden, especially when the content conflicts
+!! config
+wgCiteBookReferencing=true
+!! wikitext
+<ref name=p20>page 20</ref>
+<ref extends=book name=p20>different content</ref>
+<references>
+<ref name=book>book</ref>
+</references>
+!! html
+<p><sup id="cite_ref-p20_1-0" class="reference"><a href="#cite_note-p20-1">&#91;1&#93;</a></sup>
+<span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "p20" defined multiple times with different content</span>
+</p>
+<div class="mw-references-wrap"><ol class="references">
+<li id="cite_note-p20-1"><span class="mw-cite-backlink"><a href="#cite_ref-p20_1-0">↑</a></span> <span class="reference-text">page 20</span>
+</li>
+</ol></div>
+<p><span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: <code>&lt;ref&gt;</code> tag with name "book" defined in <code>&lt;references&gt;</code> is not used in prior text.</span>
+</p>
+!! end
+
+# TODO: T367749 - We want this to render successfully
+!! test
+T367749 - Turning a top-level ref into a subref is fine when the content is an empty string
+!! config
+wgCiteBookReferencing=true
+!! wikitext
+<ref name=p20></ref>
+<ref extends=book name=p20>page 20</ref>
+<references>
+<ref name=book>book</ref>
+</references>
+!! html
+<p><sup id="cite_ref-p20_1-0" class="reference"><a href="#cite_note-p20-1">&#91;1&#93;</a></sup>
+<span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag; name "p20" defined multiple times with different content</span>
+</p>
+<div class="mw-references-wrap"><ol class="references">
+<li id="cite_note-p20-1"><span class="mw-cite-backlink"><a href="#cite_ref-p20_1-0">↑</a></span> <span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag; no text was provided for refs named <code>p20</code></span></li>
+</ol></div>
+<p><span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: <code>&lt;ref&gt;</code> tag with name "book" defined in <code>&lt;references&gt;</code> is not used in prior text.</span>
+</p>
+!! end
+
 !! test
 T236256 - Naming book references is fine
 !! config