Added ResolvedWatcher for Units.

state/relation.go

 package state
 
-import ()
+import (
+        "fmt"
+)
 
 // RelationRole defines the role of a relation endpoint.
 type RelationRole string
 
 const (
         RoleProvider RelationRole = "provider"
         RoleRequirer RelationRole = "requirer"
         RolePeer     RelationRole = "peer"
 )
 
@@ skipping 26 matching lines @@
                 return other.RelationRole == RoleProvider
         }
         panic("endpoint role is undefined")
 }
 
 // String returns the unique identifier of the relation endpoint.
 func (e RelationEndpoint) String() string {
         return e.ServiceName + ":" + e.RelationName
 }
 
+// checkValues performs basic tests on the endpoint data without
+// checking the validity of identifiers.
+func (e *RelationEndpoint) checkValues() error {
+        switch {
+        case e.ServiceName == "":
+                return fmt.Errorf("endpoint has empty service name")
+        case e.Interface == "":
+                return fmt.Errorf("endpoint has empty interface")
+        case e.RelationName == "":
+                return fmt.Errorf("endpoint has empty relation name")
+        case e.RelationRole != RoleProvider && e.RelationRole != RoleRequirer && e.RelationRole != RolePeer:
+                return fmt.Errorf("endpoint has invalid role: %q", e.RelationRole)
+        case e.RelationScope != ScopeGlobal && e.RelationScope != ScopeContainer:
+                return fmt.Errorf("endpoint has invalid scope: %q", e.RelationScope)
+        }
+        return nil
+}
+
 // Relation represents a link between services, or within a
 // service (in the case of peer relations).
 type Relation struct {
         st  *State
         key string
 }
 
 // ServiceRelation represents an established relation from
 // the viewpoint of a participant service.
 type ServiceRelation struct {
@@ skipping 12 matching lines @@
 
 // RelationRole returns the service role within the relation.·
 func (r *ServiceRelation) RelationRole() RelationRole {
         return r.relationRole
 }
 
 // RelationName returns the name this relation has within the service.
 func (r *ServiceRelation) RelationName() string {
         return r.relationName
 }