From 5de7033a823a56ac9e56a5eadeef8d18fb1d39f4 Mon Sep 17 00:00:00 2001
From: Tom Proctor <tomhjp@users.noreply.github.com>
Date: Thu, 23 Apr 2026 14:19:44 +0100
Subject: [PATCH] util/set: add ContainsSet and ContainsAll

These are trivial methods, but useful and generally applicable operations
for a set type.

Updates #cleanup

Change-Id: I94610b901cd10fe66dd15c38b8601f29ead71811
Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>
---
 util/set/set.go      | 18 ++++++++++++
 util/set/set_test.go | 68 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/util/set/set.go b/util/set/set.go
index c3d2350a7..105e9782b 100644
--- a/util/set/set.go
+++ b/util/set/set.go
@@ -6,6 +6,7 @@ package set
 
 import (
 	"encoding/json"
+	"iter"
 	"maps"
 	"reflect"
 	"sort"
@@ -111,6 +112,23 @@ func (s Set[T]) Contains(e T) bool {
 	return ok
 }
 
+// ContainsSet reports whether s is a superset of e. Returns true if e is nil,
+// empty, or equal to s.
+func (s Set[T]) ContainsSet(e Set[T]) bool {
+	return s.ContainsAll(maps.Keys(e))
+}
+
+// ContainsAll reports whether s contains all elements of e. Returns true if e
+// has 0 elements.
+func (s Set[T]) ContainsAll(e iter.Seq[T]) bool {
+	for k := range e {
+		if !s.Contains(k) {
+			return false
+		}
+	}
+	return true
+}
+
 // Len reports the number of items in s.
 func (s Set[T]) Len() int { return len(s) }
 
diff --git a/util/set/set_test.go b/util/set/set_test.go
index 2188cbb4d..35e66bf36 100644
--- a/util/set/set_test.go
+++ b/util/set/set_test.go
@@ -5,6 +5,8 @@ package set
 
 import (
 	"encoding/json"
+	"iter"
+	"maps"
 	"slices"
 	"testing"
 )
@@ -200,3 +202,69 @@ func TestMake(t *testing.T) {
 		t.Error("missing 1")
 	}
 }
+
+func TestContainsCollection(t *testing.T) {
+	s := Of(1, 2, 3)
+	for name, tc := range map[string]struct {
+		e        []int
+		expected bool
+	}{
+		"equal": {
+			e:        []int{1, 2, 3},
+			expected: true,
+		},
+		"superset": {
+			e:        []int{2, 3},
+			expected: true,
+		},
+		"disjoint": {
+			e:        []int{4, 5},
+			expected: false,
+		},
+		"partial": {
+			e:        []int{2, 4},
+			expected: false,
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			if s.ContainsSet(Of(tc.e...)) != tc.expected {
+				t.Errorf("ContainsSet(%v) = %v; want %v", tc.e, !tc.expected, tc.expected)
+			}
+			if s.ContainsAll(slices.Values(tc.e)) != tc.expected {
+				t.Errorf("ContainsSet(%v) = %v; want %v", tc.e, !tc.expected, tc.expected)
+			}
+		})
+	}
+}
+
+// Test ContainsSet always return true for empty collections.
+func TestContainsSetEmpty(t *testing.T) {
+	var emptySets = []Set[int]{
+		nil,
+		make(Set[int]),
+		Of[int](),
+	}
+	for _, s := range []Set[int]{nil, make(Set[int]), Of[int](), Of(1, 2, 3)} {
+		for _, empty := range emptySets {
+			if !s.ContainsSet(empty) {
+				t.Errorf("set %v should contain empty set %v", s, empty)
+			}
+		}
+	}
+}
+
+// Test ContainsAll always return true for empty collections.
+func TestContainsAllEmpty(t *testing.T) {
+	var emptyIters = []iter.Seq[int]{
+		func(yield func(int) bool) {},
+		slices.Values([]int{}),
+		maps.Keys(map[int]struct{}{}),
+	}
+	for _, s := range []Set[int]{nil, make(Set[int]), Of[int](), Of(1, 2, 3)} {
+		for _, empty := range emptyIters {
+			if !s.ContainsAll(empty) {
+				t.Errorf("set %v should contain empty iterator %v", s, empty)
+			}
+		}
+	}
+}