fix: render hard line breaks

src/Tokens/TextToken.php

@@ -13,7 +13,23 @@ public function __construct(
 
     public function parse(Parser $parser): string
     {
-        return $this->content;
+        // A line ending preceded by two or more spaces, or by a backslash,
+        // is a hard line break — unless it ends the block, where it is
+        // dropped rather than rendered.
+        if (
+            ! str_contains($this->content, "\n")
+            && ! str_contains($this->content, "\r")
+        ) {
+            return $this->content;
+        }
+
+        return (
+            preg_replace(
+                '/(?: {2,}|\\\\)(\r\n|\n|\r)(?!\z)/',
+                '<br />$1',
+                $this->content,
+            ) ?? $this->content
+        );
     }
 
     public function append(string $content): void

tests/Tokens/TextTokenTest.php

@@ -4,6 +4,8 @@
 
 use PHPUnit\Framework\Attributes\Test;
 use Tempest\Markdown\Parser;
+use Tempest\Markdown\Rules\BoldRule;
+use Tempest\Markdown\Rules\TextRule;
 use Tempest\Markdown\Tests\ParserTestCase;
 use Tempest\Markdown\Tokens\TextToken;
 
@@ -16,4 +18,58 @@ public function test_parse(): void
 
         $this->assertEquals('Hello, world!', $token->parse(new Parser()));
     }
+
+    #[Test]
+    public function parse_renders_a_hard_break_after_two_spaces(): void
+    {
+        $parser = new Parser(highlighter: null, rules: [new TextRule()]);
+
+        $this->assertSame(
+            "a<br />\nb",
+            new TextToken("a  \nb")->parse($parser),
+        );
+        $this->assertSame(
+            "a<br />\nb",
+            new TextToken("a   \nb")->parse($parser),
+        );
+    }
+
+    #[Test]
+    public function parse_renders_a_hard_break_after_a_backslash(): void
+    {
+        $parser = new Parser(highlighter: null, rules: [new TextRule()]);
+
+        $this->assertSame(
+            "a<br />\nb",
+            new TextToken("a\\\nb")->parse($parser),
+        );
+    }
+
+    #[Test]
+    public function parse_keeps_a_soft_break_as_is(): void
+    {
+        $parser = new Parser(highlighter: null, rules: [new TextRule()]);
+
+        $this->assertSame("a\nb", new TextToken("a\nb")->parse($parser));
+        $this->assertSame("a \nb", new TextToken("a \nb")->parse($parser));
+    }
+
+    #[Test]
+    public function parse_drops_a_hard_break_at_the_end_of_the_content(): void
+    {
+        $parser = new Parser(highlighter: null, rules: [new TextRule()]);
+
+        $this->assertSame("a  \n", new TextToken("a  \n")->parse($parser));
+    }
+
+    #[Test]
+    public function lex_renders_a_hard_break_around_other_inline_tokens(): void
+    {
+        $html = (string) new Parser(highlighter: null, rules: [
+            new BoldRule(),
+            new TextRule(),
+        ])->parse("a **b**  \nc");
+
+        $this->assertSame("a <strong>b</strong><br />\nc", $html);
+    }
 }