Correctly get lexer for language

`get_lexer_by_name` doesn't actually get the lexer by its name...

website/contrib/code_block/blocks.py

@@ -3,7 +3,7 @@ from typing import Iterator
 from django.utils.safestring import mark_safe
 from pygments import highlight
 from pygments.formatters.html import HtmlFormatter
-from pygments.lexers import get_all_lexers, get_lexer_by_name
+from pygments.lexers import find_lexer_class, get_all_lexers
 from wagtail.blocks import (
     BooleanBlock,
     CharBlock,
@@ -21,11 +21,11 @@ def get_language_choices() -> Iterator[tuple[str, str]]:
 
 class CodeStructValue(StructValue):
     def code(self) -> str:
-        lexer = get_lexer_by_name(self.get("language"))
+        lexer = find_lexer_class(self["language"])()
         formatter = HtmlFormatter(
             linenos=None,
         )
-        return mark_safe(highlight(self.get("source"), lexer, formatter))
+        return mark_safe(highlight(self["source"], lexer, formatter))
 
 
 class CodeBlock(StructBlock):

website/contrib/code_block/tests.py

@@ -1,10 +1,11 @@
-from django.test import TestCase
+from django.test import SimpleTestCase
 from django.urls import reverse
 
+from .blocks import CodeStructValue, get_language_choices
 from .utils import PYGMENTS_VERSION_SLUG
 
 
-class PygmentsStylesTestCase(TestCase):
+class PygmentsStylesTestCase(SimpleTestCase):
     url = reverse("code-block:styles")
 
     def test_accessible(self) -> None:
@@ -15,3 +16,13 @@ class PygmentsStylesTestCase(TestCase):
 
     def test_url_contains_version(self) -> None:
         self.assertIn(PYGMENTS_VERSION_SLUG, self.url)
+
+
+class CodeStructValueTestCase(SimpleTestCase):
+    def test_highlights(self) -> None:
+        for language, _ in get_language_choices():
+            with self.subTest(language):
+                block = CodeStructValue(
+                    None, [("source", "test"), ("language", language)]
+                )
+                self.assertIsInstance(block.code(), str)