Move isExplicitMarkup helper to LineChecker and broaden test coverage

Hosts the helper next to its siblings (isLink, isDirective, isAnnotation),
aligns its regex flags with the rest of the file, and exercises
sub-section underlines, phrase-reference anchors and stacked anchors.

Author: lacatoire

packages/guides-restructured-text/src/RestructuredText/Parser/LineChecker.php

@@ -91,4 +91,15 @@ public static function isAnnotation(string $line): bool
     {
         return preg_match('/^\.\.\s+\[([#a-zA-Z0-9]*)\]\s(.*)$$/mUsi', $line) > 0;
     }
+
+    /**
+     * RST explicit markup blocks (anchors, comments, directives, ...) start with two
+     * dots followed by whitespace, or are a lonely `..`.
+     *
+     * @link https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#explicit-markup-blocks
+     */
+    public static function isExplicitMarkup(string $line): bool
+    {
+        return preg_match('/^\.\.(\s.*|)$/mUsi', $line) > 0;
+    }
 }

packages/guides-restructured-text/src/RestructuredText/Parser/Productions/TitleRule.php

@@ -24,7 +24,6 @@
 
 use function mb_strlen;
 use function min;
-use function preg_match;
 use function trim;
 
 /**
@@ -45,7 +44,7 @@ public function applies(BlockContext $blockContext): bool
         $line = $blockContext->getDocumentIterator()->current();
         $nextLine = $blockContext->getDocumentIterator()->getNextLine();
 
-        if ($this->isExplicitMarkup($line)) {
+        if (LineChecker::isExplicitMarkup($line)) {
             return false;
         }
 
@@ -113,16 +112,4 @@ private function nextLineIsAnUnderline(string $line, string|null $nextLine): str
 
         return $letter ?? '';
     }
-
-    /**
-     * RST explicit markup blocks (anchors, comments, directives, ...) start with two
-     * dots followed by whitespace, or are a lonely `..`. Such a line must never be
-     * treated as a section title, even if the next line happens to look like an underline.
-     *
-     * @see https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#explicit-markup-blocks
-     */
-    private function isExplicitMarkup(string $line): bool
-    {
-        return preg_match('/^\.\.(?:\s|$)/', $line) === 1;
-    }
 }

packages/guides-restructured-text/tests/unit/Parser/Productions/TitleRuleTest.php

@@ -59,6 +59,8 @@ public static function provideExplicitMarkupLines(): Generator
         yield 'anchor with single space' => [".. _foo:\n========\n"];
         yield 'anchor with double space' => ["..  _foo:\n========\n"];
         yield 'anchor with tab' => [".. \t_foo:\n========\n"];
+        yield 'anchor above level-2 underline' => [".. _foo:\n--------\n"];
+        yield 'phrase reference anchor' => [".. _`Foo Bar`:\n==============\n"];
         yield 'directive' => [".. note::\n=========\n"];
         yield 'comment' => [".. some comment\n===============\n"];
         yield 'lonely double dot' => ["..\n==\n"];

tests/Integration/tests/anchor/anchor-no-blank-line-stacked/expected/index.html

@@ -0,0 +1,16 @@
+<!-- content start -->
+    <div class="section" id="release-notes-1">
+            <a id="changelog"></a>
+            <a id="release-notes"></a>
+            <h1>Release Notes</h1>
+
+    <p>Some content</p>
+
+
+    <p>This points to release notes: <a href="/index.html#release-notes">Release Notes</a></p>
+
+
+    <p>This points to changelog: <a href="/index.html#changelog">Release Notes</a></p>
+
+    </div>
+<!-- content end -->

tests/Integration/tests/anchor/anchor-no-blank-line-stacked/input/index.rst

@@ -0,0 +1,10 @@
+.. _release-notes:
+.. _changelog:
+Release Notes
+=============
+
+Some content
+
+This points to release notes: :ref:`release-notes`
+
+This points to changelog: :ref:`changelog`