Add hierarchical module IDs

In preparation for submodules in Mir this commit introduces structured
module IDs. They are backwards-compatible with the old unstructured
ones, which are considered to be identifiers of top-level modules.

Signed-off-by: Matej Pavlovic <[email protected]>

pkg/types/moduleid.go

@@ -0,0 +1,31 @@
+package types
+
+import "strings"
+
+const Separator = "/"
+
+// ModuleID represents an identifier of a module.
+// It corresponds to a path in the module hierarchy.
+type ModuleID string
+
+// Pb converts a ModuleID to a type used in a Protobuf message.
+func (mid ModuleID) Pb() string {
+	return string(mid)
+}
+
+// Top returns the ID of the top-level module of the path, stripped of the IDs of the submodules.
+func (mid ModuleID) Top() ModuleID {
+	top, _, _ := strings.Cut(string(mid), Separator)
+	return ModuleID(top)
+}
+
+// Sub returns the identifier of a submodule within the top-level module, stripped of the top-level module identifier.
+func (mid ModuleID) Sub() ModuleID {
+	_, sub, _ := strings.Cut(string(mid), Separator)
+	return ModuleID(sub)
+}
+
+// Then combines the module ID with a relative path to its submodule in a single module ID.
+func (mid ModuleID) Then(submodule ModuleID) ModuleID {
+	return ModuleID(string(mid) + Separator + string(submodule))
+}

pkg/types/types.go

@@ -305,17 +305,6 @@ func (td TimeDuration) Pb() uint64 {
 	return uint64(td)
 }
 
-// ================================================================================
-
-// ModuleID represents an identifier of a module.
-// Modules are stored under their identifiers in modules.Modules
-type ModuleID string
-
-// Pb converts a ModuleID to a type used in a Protobuf message.
-func (mid ModuleID) Pb() string {
-	return string(mid)
-}
-
 // ================================================================================
 // Auxiliary functions
 // ================================================================================

workitems.go

@@ -34,7 +34,7 @@ func (wi workItems) AddEvents(events *events.EventList) error {
 	for event := iter.Next(); event != nil; event = iter.Next() {
 
 		// Look up the corresponding module's buffer and add the event to it.
-		if buffer, ok := wi[t.ModuleID(event.DestModule)]; ok {
+		if buffer, ok := wi[t.ModuleID(event.DestModule).Top()]; ok {
 			buffer.PushBack(event)
 		} else {
 			return fmt.Errorf("no buffer for module %v (adding event of type %T)", event.DestModule, event.Type)