fix(appsettings): a theme change reaches the CSS nginx serves

nginx serves STATIC_ROOT (staticfiles/) since collectstatic moved there,
but the theme view wrote only static/css/wvc-main.min.css, so a new theme
showed up only after the next collectstatic. The view now also writes the
collected copy when collectstatic has run; the source copy stays so a
later collectstatic keeps the theme.

appsettings/test_theme_name.py

@@ -2,11 +2,15 @@
 SASS_DIR/wvc-themes: it is written into @import paths and the compiled CSS."""
 
 import os
+import shutil
 import tempfile
+from pathlib import Path
 
 from appsettings.models import AppSettings
+from django.conf import settings
 from django.contrib.auth.models import User
-from django.test import TestCase
+from django.contrib.messages import get_messages
+from django.test import TestCase, override_settings
 from django.urls import reverse
 
 
@@ -54,3 +58,42 @@ class SassDirTests(TestCase):
         AppSettings.objects.filter(key="SASS_DIR").update(value=outside.name)
         self.client.post(reverse("appsettings"), {"BOOTSTRAP_THEME": "flatly"})
         self.assertFalse(os.path.exists(os.path.join(outside.name, "wvc-main.scss")))
+
+
+class ThemeCssTests(TestCase):
+    """A theme change also rewrites the collected wvc-main.min.css: nginx
+    serves STATIC_ROOT, not static/."""
+
+    def setUp(self):
+        self.client.force_login(User.objects.create_superuser("tc-admin", "tc@example.com", "pw"))
+        project = tempfile.TemporaryDirectory()
+        self.addCleanup(project.cleanup)
+        self.project = Path(project.name)
+        shutil.copytree(Path(settings.BASE_DIR, "dev", "scss"), self.project / "dev" / "scss")
+        (self.project / "static" / "css").mkdir(parents=True)
+        cwd = os.getcwd()
+        os.chdir(self.project)
+        self.addCleanup(os.chdir, cwd)
+        AppSettings.objects.filter(key="SASS_DIR").update(value="dev/scss")
+
+    def change_theme(self, static_root):
+        with override_settings(BASE_DIR=self.project, STATIC_ROOT=static_root):
+            response = self.client.post(reverse("appsettings"), {"BOOTSTRAP_THEME": "flatly"})
+        self.assertIn("Theme is changed. Now: flatly", [str(m) for m in get_messages(response.wsgi_request)])
+        self.assertEqual(AppSettings.objects.get(key="BOOTSTRAP_THEME").value, "flatly")
+        source = (self.project / "static" / "css" / "wvc-main.min.css").read_text()
+        self.assertIn(".btn", source)
+        return source
+
+    def test_the_collected_css_is_the_new_theme(self):
+        served = self.project / "staticfiles" / "css" / "wvc-main.min.css"
+        served.parent.mkdir(parents=True)
+        served.write_text("old theme")
+        self.assertEqual(served.read_text(), "old theme")
+        self.assertEqual(self.change_theme(self.project / "staticfiles"), served.read_text())
+
+    def test_without_collected_css_only_the_source_is_written(self):
+        (self.project / "staticfiles").mkdir()
+        self.change_theme(self.project / "staticfiles")
+        self.assertEqual(list((self.project / "staticfiles").iterdir()), [])
+        self.change_theme(None)

appsettings/views.py

@@ -93,6 +93,10 @@ def appsettings(request):
                 )
                 with open("static/css/" + main_css, "w") as css:
                     css.write(css_compressed)
+                # nginx serves the collected copy; collectstatic later takes it from static/
+                served = Path(settings.STATIC_ROOT or "", "css")
+                if settings.STATIC_ROOT and served.is_dir():
+                    (served / main_css).write_text(css_compressed)
 
                 bootstrap_theme.value = theme
                 bootstrap_theme.save()