fix: handling of placeholder models in dependency injection

The placeholder models (of which the most obvious instance is the profile tag)
were handled as normal component models by DependencyInjection. This led to
their selection to be reduced to component models as well, which fails if there
are ambiguities and one want to select a particular service, that is

   some_tag => component_m.my_srv

Rewrite the selection logic to use the placeholder-friendly API
(each_required_model and fullfills?)

Author: doudou

lib/syskit/dependency_injection.rb

@@ -202,31 +202,65 @@ def self.normalize_selection(selection)
                     next
                 end
 
-                if value.respond_to?(:fullfills?) && !value.fullfills?(key)
-                    raise ArgumentError,
-                          "found #{value.name}(of class #{value.class}) " \
-                          "as a selection for #{key.name}, but " \
-                          "#{value.name} does not fullfill #{key.name}"
+                normalized[key] = normalize_component_model_selection(key, value)
+            end
+            normalized
+        end
+
+        # @api private
+        #
+        # Helper for normalize_selection when the key is a component model (e.g.
+        # "real" component model, data service model or placeholder model)
+        #
+        # @param [Class<AbstractComponent>] key
+        # @param [String,SpecialDIValue,#fullfills?] value
+        # @return [String,SpecialDIValue,#fullfills?] normalized selected value
+        def self.normalize_component_model_selection(key, value)
+            if value.respond_to?(:to_str)
+                return value
+            elsif value.kind_of?(SpecialDIValue)
+                return value
+            end
+
+            unless value.fullfills?(key)
+                raise ArgumentError,
+                      "found #{value.name}(of class #{value.class}) " \
+                      "as a selection for #{key.name}, but " \
+                      "#{value.name} does not fullfill #{key.name}"
+            end
+
+            required_component_m = nil
+            required_services_m = []
+            required_component_m, required_services_m =
+                key.each_required_model.partition do |m|
+                    m <= Component
                 end
+            if required_services_m.size > 1
+                raise NotImplementedError,
+                      "there is no support (yet) to select for multiple services"
+            elsif !required_component_m && required_services_m.empty?
+                raise NotImplementedError, "nothing to select in #{key}"
+            end
 
-                if key <= Component
-                    if value.kind_of?(Models::BoundDataService)
-                        value = value.component_model
-                    elsif value.kind_of?(Syskit::BoundDataService)
-                        value = value.component
-                    end
-                    normalized[key] = value
-                elsif key <= DataService
-                    if value.respond_to?(:find_data_service_from_type)
-                        value = value.find_data_service_from_type(key)
-                    end
-                    normalized[key] = value
-                else
-                    raise NotImplementedError,
-                          "should not have get there, but did"
+            required_component_m = required_component_m.first
+            required_service_m = required_services_m.first
+
+            if required_service_m && !required_component_m
+                if value.respond_to?(:find_data_service_from_type)
+                    value =
+                        value.find_data_service_from_type(required_services_m.first)
+                end
+
+                value
+            else
+                if value.kind_of?(Models::BoundDataService)
+                    value = value.component_model
+                elsif value.kind_of?(Syskit::BoundDataService)
+                    value = value.component
                 end
+
+                value
             end
-            normalized
         end
 
         # Add a list of objects to the default list.