Ignore pygments_formatter in fenced_code attribute lists

docs/changelog.md

@@ -35,6 +35,9 @@ See the [Contributing Guide](contributing.md) for details.
   and closing backticks did not match (#1668).
 * Escape the language name in the `codehilite` extension's non-Pygments output to
   maintain consistency with Pygments output.
+* Ignore a `pygments_formatter` key in a fenced code block's attribute list so
+  the formatter is always the one set in the `codehilite` configuration. A
+  formatter such as `text` would otherwise leave the code unescaped.
 * Preserve attributes without a value in the `attr_list` extension exactly as
   provided, rather than rendering them as `key="key"`, so the same source
   renders consistently under both the `html` and `xhtml` output formats

markdown/extensions/fenced_code.py

@@ -126,6 +126,9 @@ def run(self, lines: list[str]) -> list[str]:
                 # is enabled, so we call it to highlight the code
                 if self.codehilite_conf and self.codehilite_conf['use_pygments'] and config.get('use_pygments', True):
                     local_config = self.codehilite_conf.copy()
+                    # Only the `codehilite` configuration may set the formatter, as some
+                    # formatters (such as `text`) do not escape the code.
+                    config.pop('pygments_formatter', None)
                     local_config.update(config)
                     # Combine classes with `cssclass`. Ensure `cssclass` is at end
                     # as Pygments appends a suffix under certain circumstances.

tests/test_syntax/extensions/test_fenced_code.py

@@ -1079,3 +1079,29 @@ def testInvalidCustomPygmentsFormatter(self):
                 'fenced_code'
             ]
         )
+
+    def testFencedLanguageAttrPygmentsFormatterIgnored(self):
+        # The formatter can only be set in the `codehilite` configuration.
+        if has_pygments:
+            expected = self.dedent(
+                '''
+                <div class="codehilite"><pre><span></span><code>&lt;b&gt;Some HTML&lt;/b&gt;
+                </code></pre></div>
+                '''
+            )
+        else:
+            expected = (
+                '<pre class="codehilite"><code class="language-text">&lt;b&gt;Some HTML&lt;/b&gt;\n'
+                '</code></pre>'
+            )
+        self.assertMarkdownRenders(
+            self.dedent(
+                '''
+                ``` { .text pygments_formatter='text' }
+                <b>Some HTML</b>
+                ```
+                '''
+            ),
+            expected,
+            extensions=['codehilite', 'fenced_code']
+        )