mediawiki: Make retrieving list of supported languages robust

- Invoke PHP command to retrieve the list instead of parsing PHP file. This
fixes issue with regex not being generic enough to retrieve languages list using
double quotes. Also make is much more robust to future formatting changes.

- If there is an error in retrieving, which may happen due to future code
changes, fall back to showing a safe list of languages instead of making the app
unusable.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/mediawiki/forms.py

@@ -3,13 +3,17 @@
 FreedomBox app for configuring MediaWiki.
 """
 
+import json
+import logging
 import pathlib
-import re
+import subprocess
 
 from django import forms
 from django.core import validators
 from django.utils.translation import gettext_lazy as _
 
+from . import privileged
+
 
 def get_skins():
     """Return a list of available skins as choice field values."""
@@ -31,12 +35,19 @@ def get_languages():
     if not names_old.exists():
         names_file = names_new
 
-    with open(names_file, 'r') as lang_file:
-        content = lang_file.read()
-    matches = re.findall(r"'([a-z_-]+)' => '(.+)', # .+", content)
-    language_choices = [(code, name) for code, name in matches]
-
-    return language_choices
+    script = rf'''<?php
+    require_once('{names_file}');
+    print(json_encode(Mediawiki\Languages\Data\Names::$names));'''
+    try:
+        process = subprocess.run([privileged.get_php_command()],
+                                 input=script.encode(), stdout=subprocess.PIPE,
+                                 check=True)
+        languages_dict = json.loads(process.stdout.decode())
+        return list(languages_dict.items())
+    except Exception as exception:
+        logging.exception('Unable read list of Mediawiki languages.',
+                          exception)
+        return [('en', 'English')]
 
 
 class MediaWikiForm(forms.Form):  # pylint: disable=W0232