setup: Show and remove conflicts before installation

Warn of installed conflicting packages before installing apps.

[sunil: Rename 'advice' to 'action']
[sunil: Action will be string constant, for better API and i18n]
[sunil: Don't show conflict warning if action is 'ignore']
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/setup.py

@@ -13,6 +13,7 @@ from collections import defaultdict
 import apt
 
 import plinth
+from plinth.package import packages_installed
 from plinth.signals import post_setup
 
 from . import package
@@ -178,6 +179,15 @@ class Helper(object):
                             if pkg_name not in cache)
         return any(unavailable_pkgs)
 
+    def get_package_conflicts(self):
+        """Report list of conflicting packages for the user."""
+        package_conflicts, package_conflicts_action = \
+            _get_module_package_conflicts(self.module)
+        if package_conflicts:
+            package_conflicts = packages_installed(package_conflicts)
+
+        return package_conflicts, package_conflicts_action
+
 
 def init(module_name, module):
     """Create a setup helper for a module for later use."""
@@ -298,6 +308,12 @@ def _is_module_essential(module):
     return getattr(module, 'is_essential', False)
 
 
+def _get_module_package_conflicts(module):
+    """Return list of packages that conflict with packages of a module."""
+    return (getattr(module, 'package_conflicts',
+                    None), getattr(module, 'package_conflicts_action', None))
+
+
 def _get_module_managed_packages(module):
     """Return list of packages managed by a module."""
     return getattr(module, 'managed_packages', [])

plinth/templates/setup.html

@@ -50,6 +50,17 @@
             <span class="fa fa-refresh"></span> {% trans "Check again" %}
           </button>
         </div>
+      {% elif package_conflicts and package_conflicts_action != 'ignore' %}
+        <div class="alert alert-warning" role="alert">
+          {% blocktrans trimmed %}
+            <strong>Conflicting Packages:</strong> Some packages installed on
+            the system conflict with the installation of this app. The following
+            packages will be removed if you proceed:
+          {% endblocktrans %}
+          {% for package in package_conflicts %}
+            {{ package }}
+          {% endfor %}
+        </div>
       {% endif %}
 
       <input type="submit" class="btn btn-md btn-primary" name="install"

plinth/views.py

@@ -275,11 +275,17 @@ class SetupView(TemplateView):
         context['setup_helper'] = setup_helper
         context['app_info'] = setup_helper.module.app.info
 
+        # Report any installed conflicting packages that will be removed.
+        package_conflicts, package_conflicts_action = \
+            setup_helper.get_package_conflicts()
+        context['package_conflicts'] = package_conflicts
+        context['package_conflicts_action'] = package_conflicts_action
+
         # Reuse the value of setup_state throughout the view for consistency.
         context['setup_state'] = setup_helper.get_state()
         context['setup_current_operation'] = setup_helper.current_operation
 
-        # Perform expensive operation only if needed
+        # Perform expensive operation only if needed.
         if not context['setup_current_operation']:
             context[
                 'package_manager_is_busy'] = package.is_package_manager_busy()