2 files changed, 31 insertions, 0 deletions
diff --git a/pkg/subsystem/entities.go b/pkg/subsystem/entities.go
index 05032e6c2..1f7456e84 100644
--- a/pkg/subsystem/entities.go
+++ b/pkg/subsystem/entities.go
@@ -31,6 +31,19 @@ func (subsystem *Subsystem) ReachableParents() map[*Subsystem]struct{} {
 	return ret
 }
 
+// Emails returns the list of emails related to the subsystem.
+func (subsystem *Subsystem) Emails() []string {
+	ret := []string{}
+	// For the subsystem itself, we take both lists and maintainers.
+	ret = append(ret, subsystem.Lists...)
+	ret = append(ret, subsystem.Maintainers...)
+	// For its parent subsystems, we only take lists.
+	for parent := range subsystem.ReachableParents() {
+		ret = append(ret, parent.Lists...)
+	}
+	return ret
+}
+
 // PathRule describes the part of the directory tree belonging to a single subsystem.
 type PathRule struct {
 	IncludeRegexp string
diff --git a/pkg/subsystem/entities_test.go b/pkg/subsystem/entities_test.go
index df65dbd5a..58166b91b 100644
--- a/pkg/subsystem/entities_test.go
+++ b/pkg/subsystem/entities_test.go
@@ -21,3 +21,21 @@ func TestReachableParents(t *testing.T) {
 	}
 	assert.ElementsMatch(t, retParents, []*Subsystem{parentA, parentB, parentParent})
 }
+
+func TestSubsystemEmails(t *testing.T) {
+	parentParent := &Subsystem{Lists: []string{"a@list.com"}, Maintainers: []string{"a@person.com"}}
+	parent1 := &Subsystem{Lists: []string{"b@list.com"}, Maintainers: []string{"b@person.com"}}
+	parent2 := &Subsystem{
+		Lists:       []string{"c@list.com"},
+		Maintainers: []string{"c@person.com"},
+		Parents:     []*Subsystem{parentParent},
+	}
+	subsystem := &Subsystem{
+		Lists:       []string{"d@list.com"},
+		Maintainers: []string{"d@person.com"},
+		Parents:     []*Subsystem{parent1, parent2},
+	}
+	assert.ElementsMatch(t, subsystem.Emails(), []string{
+		"a@list.com", "b@list.com", "c@list.com", "d@list.com", "d@person.com",
+	})
+}