[libcalamaresui] Adjust the emergency-ness of modules

A potentially emergency module is one that has EMERGENCY
(in CMake) or emergency: true (in module.desc) set.
Any such module must also set emergency: true in the
configuration of the module. This is to allow for
instances of a module that **don't** run as emergency
modules, alongside actual emergency ones.

src/libcalamaresui/modulesystem/Module.cpp

@@ -52,6 +52,8 @@ name:      "foo"      #the module name. must be unique and same as the parent di
 interface: "qtplugin" #can be: qtplugin, python, process, ...
 */
 
+static const char EMERGENCY[] = "emergency";
+
 namespace Calamares
 {
 
@@ -198,6 +200,9 @@ Module::loadConfigurationFile( const QString& configFileName ) //throws YAML::Ex
             }
 
             m_configurationMap = CalamaresUtils::yamlMapToVariant( doc ).toMap();
+            m_emergency = m_maybe_emergency
+                && m_configurationMap.contains( EMERGENCY )
+                && m_configurationMap[ EMERGENCY ].toBool();
             return;
         }
         else
@@ -291,10 +296,9 @@ Module::initFrom( const QVariantMap& moduleDescriptor )
 {
     m_name = moduleDescriptor.value( "name" ).toString();
 
-    auto em = QStringLiteral( "emergency" );
-    if ( moduleDescriptor.contains( em ) )
+    if ( moduleDescriptor.contains( EMERGENCY ) )
     {
-        m_emergency = moduleDescriptor[ em ].toBool();
+        m_maybe_emergency = moduleDescriptor[ EMERGENCY ].toBool();
     }
 }
 

src/libcalamaresui/modulesystem/Module.h

@@ -185,7 +185,8 @@ protected:
     QVariantMap m_configurationMap;
 
     bool m_loaded = false;
-    bool m_emergency = false;
+    bool m_emergency = false;  // Based on module and local config
+    bool m_maybe_emergency = false;  // Based on the module.desc
 
 private:
     void loadConfigurationFile( const QString& configFileName ); //throws YAML::Exception

src/modules/README.md

@@ -145,3 +145,9 @@ processing continues.
 
 Use the EMERGENCY keyword in the CMake description of a C++ module
 to generate a suitable `module.desc`.
+
+A module that is marked as an emergency module in its module.desc
+must **also** set the *emergency* key to *true* in its configuration file.
+If it does not, the module is not considered to be an emergency module
+after all (this is so that you can have modules that have several
+instances, only some of which are actually needed for emergencies.