package: Don't consider uninstalled packages as available

- Ensure that packages that are not installable to negative priority are not
shown as available.

Tests:

- Set priority of an available package to less than 0. This package will be
shown as not-available in the app install page.

- Normal apps are shown as available and can be installed as usual.

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

plinth/package.py

@@ -69,8 +69,11 @@ class Package(PackageExpression):
 
     def actual(self) -> str:
         cache = apt.Cache()
-        if self.name in cache:
+        if self.name in cache and cache[self.name].candidate:
-            # TODO: Also return version and suite to install from
+            # cache[package].candidate returns installation candidate. If the
+            # package is not installable due to the available versions being of
+            # priority less than 0, then .candidate will be None. TODO: Also
+            # return version and suite to install from.
             return self.name
 
         raise MissingPackageError(self.name)

plinth/tests/test_package.py

@@ -80,11 +80,21 @@ def test_packages_init():
     assert component.rerun_setup_on_upgrade
 
 
-def test_packages_get_actual_packages():
+@patch('apt.Cache')
+def test_packages_get_actual_packages(cache):
     """Test resolving of package expressions to actual packages."""
+    cache.return_value = {
+        'python3': Mock(name='python3', candidate='1.0'),
+        'janus': Mock(name='janus', candidate=None)
+    }
+
     component = Packages('test-component', ['python3'])
     assert component.get_actual_packages() == ['python3']
 
+    component = Packages('test-component', ['unknown-package'])
+    with pytest.raises(MissingPackageError):
+        component.get_actual_packages()
+
     component = Packages('test-component',
                          [Package('unknown-package') | Package('python3')])
     assert component.get_actual_packages() == ['python3']
@@ -94,6 +104,10 @@ def test_packages_get_actual_packages():
                          conflicts_action=Packages.ConflictsAction.IGNORE)
     assert component.get_actual_packages() == []
 
+    component = Packages('test-component', ['janus'])
+    with pytest.raises(MissingPackageError):
+        component.get_actual_packages()
+
 
 @patch('plinth.package.install')
 def test_packages_setup(install):
@@ -356,17 +370,23 @@ def test_packages_is_available(path_class, cache, refresh_package_lists):
             '/etc/apt/sources.list': sources_list
         }[path]
 
+    def get_cache_packages(packages):
+        return {
+            package: Mock(name=package, candidate='1.0')
+            for package in packages
+        }
+
     path_class.side_effect = path_side_effect
 
     # Packages found in cache
     component = Packages('test-component', ['package1', 'package2'])
-    cache.return_value = ['package1', 'package2']
+    cache.return_value = get_cache_packages(['package1', 'package2'])
     assert component.is_available()
     path_class.assert_not_called()
     refresh_package_lists.assert_not_called()
 
     # Packages not found, cache exists and is fresh
-    cache.return_value = ['package1']
+    cache.return_value = get_cache_packages(['package1'])
     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
@@ -374,13 +394,13 @@ def test_packages_is_available(path_class, cache, refresh_package_lists):
     refresh_package_lists.assert_not_called()
 
     # Packages not found, cache does not exist
-    cache.return_value = ['package1']
+    cache.return_value = get_cache_packages(['package1'])
     package_cache.exists.return_value = False
     assert not component.is_available()
     refresh_package_lists.assert_called_once()
 
     # Packages not found, cache is stale because it older than 1 hour
-    cache.return_value = ['package1']
+    cache.return_value = get_cache_packages(['package1'])
     refresh_package_lists.reset_mock()
     package_cache.exists.return_value = True
     package_cache.stat.return_value.st_mtime = time.time() - 7200
@@ -388,7 +408,7 @@ def test_packages_is_available(path_class, cache, refresh_package_lists):
     refresh_package_lists.assert_called_once()
 
     # Packages not found, cache is stale because it older than sources.list
-    cache.return_value = ['package1']
+    cache.return_value = get_cache_packages(['package1'])
     refresh_package_lists.reset_mock()
     package_cache.exists.return_value = True
     package_cache.stat.return_value.st_mtime = time.time() - 100
@@ -397,7 +417,10 @@ def test_packages_is_available(path_class, cache, refresh_package_lists):
     refresh_package_lists.assert_called_once()
 
     # Packages not found, cache is stale, but packages found after refresh
-    cache.side_effect = [['package1'], ['package1', 'package2']]
+    cache.side_effect = [
+        get_cache_packages(['package1']),
+        get_cache_packages(['package1', 'package2'])
+    ]
     refresh_package_lists.reset_mock()
     assert component.is_available()