package: Refresh apt cache if sources list is newer

- When backports repository or unstable repository freshly added by the updates
app. We will like apps to become available due to newly available Debian
packages. For this to happen 'apt update' must be called before checking if an
app is available.

Tests:

- Freshly apply the patches for upgrades app. Setup is re-run and unstable
sources file is introduced. Immediately visit the Matrix app and notice that is
shown as available and can be installed immediately.

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

plinth/package.py

@@ -268,11 +268,23 @@ class Packages(app_module.FollowerComponent):
         except MissingPackageError:
             pass  # We will retry after refreshing package list
 
-        # If the package cache is new, then package is really not available.
         package_cache = pathlib.Path('/var/cache/apt/pkgcache.bin')
-        if (package_cache.exists()
-                and time.time() - package_cache.stat().st_mtime < 3600):
-            return False
+        if package_cache.exists():
+            package_cache_mtime = package_cache.stat().st_mtime
+
+            sources_dir = pathlib.Path('/etc/apt/sources.list.d')
+            source_files = ([pathlib.Path('/etc/apt/sources.list')] +
+                            list(sources_dir.glob('*.list')) +
+                            list(sources_dir.glob('*.sources')))
+            are_sources_newer = any(
+                source_file.stat().st_mtime > package_cache_mtime
+                for source_file in source_files)
+
+            # If the package cache is new, then package is really not
+            # available.
+            if (time.time() - package_cache.stat().st_mtime < 3600
+                    and not are_sources_newer):
+                return False
 
         # Perform 'apt-get update'
         refresh_package_lists()

plinth/tests/test_package.py

@@ -344,8 +344,19 @@ def test_packages_find_conflicts(packages_installed_):
 @patch('pathlib.Path')
 def test_packages_is_available(path_class, cache, refresh_package_lists):
     """Test checking for available packages."""
-    path = Mock()
-    path_class.return_value = path
+    package_cache = Mock()
+    sources_dir = Mock()
+    sources_dir.glob.return_value = []
+    sources_list = Mock()
+
+    def path_side_effect(path):
+        return {
+            '/var/cache/apt/pkgcache.bin': package_cache,
+            '/etc/apt/sources.list.d': sources_dir,
+            '/etc/apt/sources.list': sources_list
+        }[path]
+
+    path_class.side_effect = path_side_effect
 
     # Packages found in cache
     component = Packages('test-component', ['package1', 'package2'])
@@ -356,22 +367,32 @@ def test_packages_is_available(path_class, cache, refresh_package_lists):
 
     # Packages not found, cache exists and is fresh
     cache.return_value = ['package1']
-    path.exists.return_value = True
-    path.stat.return_value.st_mtime = time.time()
+    package_cache.exists.return_value = True
+    package_cache.stat.return_value.st_mtime = time.time()
+    sources_list.stat.return_value.st_mtime = time.time() - 100
     assert not component.is_available()
     refresh_package_lists.assert_not_called()
 
     # Packages not found, cache does not exist
     cache.return_value = ['package1']
-    path.exists.return_value = False
+    package_cache.exists.return_value = False
     assert not component.is_available()
     refresh_package_lists.assert_called_once()
 
-    # Packages not found, cache is stale
+    # Packages not found, cache is stale because it older than 1 hour
     cache.return_value = ['package1']
     refresh_package_lists.reset_mock()
-    path.exists.return_value = True
-    path.stat.return_value.st_mtime = time.time() - 7200
+    package_cache.exists.return_value = True
+    package_cache.stat.return_value.st_mtime = time.time() - 7200
+    assert not component.is_available()
+    refresh_package_lists.assert_called_once()
+
+    # Packages not found, cache is stale because it older than sources.list
+    cache.return_value = ['package1']
+    refresh_package_lists.reset_mock()
+    package_cache.exists.return_value = True
+    package_cache.stat.return_value.st_mtime = time.time() - 100
+    sources_list.stat.return_value.st_mtime = time.time()
     assert not component.is_available()
     refresh_package_lists.assert_called_once()