fix: end an HTML comment on the closing string

src/Rules/HtmlCommentRule.php

@@ -19,9 +19,11 @@ public function shouldParse(Parser $parser): bool
 
     public function parse(Parser $parser): Token
     {
-        $buffer = $parser->consumeWhile('<!--');
-        $buffer .= $parser->consumeUntil('-->');
-        $buffer .= $parser->consumeWhile('-->');
+        // consumeUntil() takes a set of characters, so it stops on the first
+        // `-` in the body; a comment ends at the `-->` string.
+        $buffer = $parser->consume(4);
+        $buffer .= $parser->consumeUntilString('-->');
+        $buffer .= $parser->consume(3);
 
         return new HtmlCommentToken($buffer);
     }

tests/Rules/HtmlCommentRuleTest.php

@@ -35,6 +35,36 @@ public function test_lex_multiline(): void
         $this->assertSame($comment, $html);
     }
 
+    #[Test]
+    public function lex_a_body_holding_a_dash(): void
+    {
+        $parser = new Parser(highlighter: null, rules: [new HtmlCommentRule()]);
+
+        $this->assertSame(
+            '<!--start-show-more-->',
+            (string) $parser->parse('<!--start-show-more-->'),
+        );
+        $this->assertSame(
+            '<!-- a - b -->',
+            (string) $parser->parse('<!-- a - b -->'),
+        );
+        $this->assertSame(
+            '<!-- a > b < c -->',
+            (string) $parser->parse('<!-- a > b < c -->'),
+        );
+    }
+
+    #[Test]
+    public function lex_an_unterminated_comment(): void
+    {
+        $html =
+            (string) new Parser(highlighter: null, rules: [new HtmlCommentRule()])->parse(
+                '<!-- never closed',
+            );
+
+        $this->assertSame('<!-- never closed', $html);
+    }
+
     #[Test]
     public function test_lex_with_surrounding_content(): void
     {