Fail early on nested extends="…", if possible

This partly reverts Ied2e3f5. I haven't properly tested this before.
Rendering a bad extends (that extends a <ref> that's already extended)
not indented messes the order up and rips other extended <ref>s out of
context.

For now it might be better to stick to the previous, "magic" behavior:
Such an extends behaves like it is extending the *parent*, and is
ordered and indented as such. This is still not correct, but I feel
this is much better than rendering such a bad extends on the top level.

This patch also makes the code fail much earlier for a nested extends,
if this decision can be made already. In this case the error message is
rendered in the middle of the text (as other errors also are), not in
the <references> section.

Change-Id: I33c6a763cd6c11df09d10dfab73f955ed15e9d36

src/Cite.php

@@ -172,10 +172,18 @@ class Cite {
 			return StatusValue::newFatal( 'cite_error_ref_numeric_key' );
 		}
 
-		global $wgCiteBookReferencing;
-		// Temporary feature flag until mainstreamed.  See T236255
-		if ( !$wgCiteBookReferencing && $extends ) {
-			return StatusValue::newFatal( 'cite_error_ref_too_many_keys' );
+		if ( $extends ) {
+			// Temporary feature flag until mainstreamed, see T236255
+			global $wgCiteBookReferencing;
+			if ( !$wgCiteBookReferencing ) {
+				return StatusValue::newFatal( 'cite_error_ref_too_many_keys' );
+			}
+
+			$groupRefs = $this->referenceStack->getGroupRefs( $group );
+			if ( isset( $groupRefs[$extends]['extends'] ) ) {
+				// TODO: Introduce a specific error for this case, reuse in referencesFormat()!
+				return StatusValue::newFatal( 'cite_error_ref_too_many_keys' );
+			}
 		}
 
 		if ( $follow && ( $name || $extends ) ) {

src/FootnoteBodyFormatter.php

@@ -58,7 +58,7 @@ class FootnoteBodyFormatter {
 	}
 
 	/**
-	 * @param array $groupRefs
+	 * @param array[] $groupRefs
 	 * @param bool $responsive
 	 * @param bool $isSectionPreview
 	 * @return string
@@ -92,8 +92,8 @@ class FootnoteBodyFormatter {
 			if ( isset( $value['extends'] ) &&
 				isset( $groupRefs[$value['extends']]['extends'] )
 			) {
-				unset( $value['extends'] );
-				$value['text'] = ( $value['text'] ?? '' ) .
+				$value['text'] = ( $value['text'] ?? '' ) . ' ' .
+					// TODO: Introduce a specific error for this case; reuse in validateRef()!
 					$this->errorReporter->plain( 'cite_error_ref_too_many_keys' );
 			}
 

src/ReferenceStack.php

@@ -391,11 +391,11 @@ class ReferenceStack {
 	/**
 	 * Return all references for a group.
 	 *
-	 * @param string $group
+	 * @param ?string $group
 	 * @return array[]
 	 */
-	public function getGroupRefs( string $group ) : array {
-		return $this->refs[$group] ?? [];
+	public function getGroupRefs( ?string $group ) : array {
+		return $this->refs[$group ?? Cite::DEFAULT_GROUP] ?? [];
 	}
 
 	/**

tests/parser/bookReferencing.txt

@@ -165,7 +165,7 @@ wgCiteBookReferencing=true
 !! end
 
 !! test
-T236256 - Can't extend a book reference (no nesting).
+T236256 - Can't extend a book reference (no nesting)
 !! config
 wgCiteBookReferencing=true
 !! wikitext
@@ -176,16 +176,39 @@ wgCiteBookReferencing=true
 !! html/php
 <p><sup id="cite_ref-a_1-0" class="reference"><a href="#cite_note-a-1">&#91;1&#93;</a></sup>
 <sup id="cite_ref-b_2-0" class="reference"><a href="#cite_note-b-2">&#91;1.1&#93;</a></sup>
-<sup id="cite_ref-3" class="reference"><a href="#cite_note-3">&#91;1.1&#93;</a></sup>
+<span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag;
+invalid names, e.g. too many</span>
 </p>
 <div class="mw-references-wrap"><ol class="references">
 <li id="cite_note-a-1"><span class="mw-cite-backlink"><a href="#cite_ref-a_1-0">↑</a></span> <span class="reference-text">book</span>
 <ol class="mw-extended-references"><li id="cite_note-b-2"><span class="mw-cite-backlink"><a href="#cite_ref-b_2-0">↑</a></span> <span class="reference-text">page 2</span>
 </li>
 </ol></li>
-<li id="cite_note-3"><span class="mw-cite-backlink"><a href="#cite_ref-3">↑</a></span> <span class="reference-text">section 3<span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag;
+</ol></div>
+!! end
+
+!! test
+T236256 - Can't extend a book reference (no nesting), specified in reverse order
+!! config
+wgCiteBookReferencing=true
+!! wikitext
+<ref extends="b">section 3</ref>
+<ref extends="a" name="b">page 2</ref>
+<ref name="a">book</ref>
+<references />
+!! html/php
+<p><sup id="cite_ref-1" class="reference"><a href="#cite_note-1">&#91;1.1&#93;</a></sup>
+<sup id="cite_ref-b_2-0" class="reference"><a href="#cite_note-b-2">&#91;1.1&#93;</a></sup>
+<sup id="cite_ref-a_3-0" class="reference"><a href="#cite_note-a-3">&#91;1&#93;</a></sup>
+</p>
+<div class="mw-references-wrap"><ol class="references">
+<li id="cite_note-a-3"><span class="mw-cite-backlink"><a href="#cite_ref-a_3-0">↑</a></span> <span class="reference-text">book</span>
+<ol class="mw-extended-references"><li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text">section 3 <span class="error mw-ext-cite-error" lang="en" dir="ltr">Cite error: Invalid <code>&lt;ref&gt;</code> tag;
 invalid names, e.g. too many</span></span>
 </li>
+<li id="cite_note-b-2"><span class="mw-cite-backlink"><a href="#cite_ref-b_2-0">↑</a></span> <span class="reference-text">page 2</span>
+</li>
+</ol></li>
 </ol></div>
 !! end
 

tests/phpunit/unit/FootnoteBodyFormatterTest.php

@@ -124,9 +124,9 @@ class FootnoteBodyFormatterTest extends MediaWikiUnitTestCase {
 				],
 				'<div class="mw-references-wrap"><ol class="references">' . "\n" .
 					'<li>(cite_references_link_many|||<span class="reference-text">t3</span>' . "\n" .
-					"|)</li>\n<li>(cite_references_link_many|||" .
-					'<span class="reference-text">t1["cite_error_ref_too_many_keys"]</span>' .
-					"\n" . '|)<ol class="mw-extended-references">' .
+					'|)<ol class="mw-extended-references"><li>(cite_references_link_many|||' .
+					'<span class="reference-text">t1 ["cite_error_ref_too_many_keys"]</span>' .
+					"\n|)</li>\n" .
 					'<li>(cite_references_link_many|||<span class="reference-text">t2</span>' .
 					"\n|)</li>\n</ol></li>\n" .
 					'</ol></div>'