Add Split method to SetBuilder

internal/transport/gnmiext/client.go

@@ -116,6 +116,21 @@ func (b *SetBuilder) Limit(n int) *SetBuilder {
 	return b
 }
 
+// Split partitions operations by a predicate. Matching ops go into the
+// first builder, the rest into the second. Both inherit the limit.
+func (b *SetBuilder) Split(fn func(DataElement) bool) (match, rest *SetBuilder) {
+	match = &SetBuilder{limit: b.limit}
+	rest = &SetBuilder{limit: b.limit}
+	for _, op := range b.ops {
+		if fn(op.el) {
+			match.ops = append(match.ops, op)
+		} else {
+			rest.ops = append(rest.ops, op)
+		}
+	}
+	return match, rest
+}
+
 //go:generate go tool moq -with-resets -out client_mock.go . Client
 
 type Client interface {

internal/transport/gnmiext/client_test.go

@@ -1273,6 +1273,57 @@ func TestClient_Do(t *testing.T) {
 	}
 }
 
+func TestSetBuilder_Split(t *testing.T) {
+	a := new(Hostname("a"))
+	b := new(Hostname("b"))
+	c := new(DefaultableHostname("c"))
+	d := new(Hostname("d"))
+
+	builder := new(SetBuilder).Limit(5).
+		Update(a).
+		Patch(b).
+		Delete(c).
+		Update(d)
+
+	match, rest := builder.Split(func(el DataElement) bool {
+		_, ok := el.(*DefaultableHostname)
+		return ok
+	})
+
+	// match should contain only the DefaultableHostname
+	if len(match.ops) != 1 {
+		t.Fatalf("Split() match: got %d ops, want 1", len(match.ops))
+	}
+	if match.ops[0].el != c {
+		t.Errorf("Split() match[0]: got %v, want %v", match.ops[0].el, c)
+	}
+	if match.ops[0].mode != del {
+		t.Errorf("Split() match[0].mode: got %v, want del", match.ops[0].mode)
+	}
+
+	// rest should contain the other three
+	if len(rest.ops) != 3 {
+		t.Fatalf("Split() rest: got %d ops, want 3", len(rest.ops))
+	}
+	if rest.ops[0].el != a || rest.ops[0].mode != replace {
+		t.Errorf("Split() rest[0]: got %v/%v, want a/replace", rest.ops[0].el, rest.ops[0].mode)
+	}
+	if rest.ops[1].el != b || rest.ops[1].mode != update {
+		t.Errorf("Split() rest[1]: got %v/%v, want b/update", rest.ops[1].el, rest.ops[1].mode)
+	}
+	if rest.ops[2].el != d || rest.ops[2].mode != replace {
+		t.Errorf("Split() rest[2]: got %v/%v, want d/replace", rest.ops[2].el, rest.ops[2].mode)
+	}
+
+	// Both inherit the limit
+	if match.limit != 5 {
+		t.Errorf("Split() match.limit: got %d, want 5", match.limit)
+	}
+	if rest.limit != 5 {
+		t.Errorf("Split() rest.limit: got %d, want 5", rest.limit)
+	}
+}
+
 func TestStringToStructuredPath(t *testing.T) {
 	tests := []struct {
 		name    string