Backport of paginator: fix tokenizer comparison of composite index and ID (#25792) (#25793)

Co-authored-by: Chris Roberts <[email protected]>

Author: hc-github-team-nomad-core

.changelog/25792.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+api: Fixed pagination bug which could result in duplicate results
+```

nomad/state/paginator/tokenizer.go

@@ -7,6 +7,7 @@ import (
 	"cmp"
 	"fmt"
 	"strconv"
+	"strings"
 )
 
 // Tokenizer is the interface that must be implemented to provide pagination
@@ -45,7 +46,32 @@ func CreateIndexAndIDTokenizer[T idAndCreateIndexGetter](target string) Tokenize
 		index := item.GetCreateIndex()
 		id := item.GetID()
 		token := fmt.Sprintf("%d.%s", index, id)
-		return token, cmp.Compare(token, target)
+
+		// Split the target to extract the create index and the ID values.
+		targetParts := strings.SplitN(target, ".", 2)
+		// If the target wasn't composed of both parts, directly compare.
+		if len(targetParts) < 2 {
+			return token, cmp.Compare(token, target)
+		}
+
+		// Convert the create index to an integer for comparison. This
+		// prevents a lexigraphical comparison of the create index which
+		// can cause unexpected results when comparing index values like
+		// '12' and '102'. If the index cannot be converted to an integer,
+		// fall back to direct comparison.
+		targetIndex, err := strconv.Atoi(targetParts[0])
+		if err != nil {
+			return token, cmp.Compare(token, target)
+		}
+
+		indexCmp := cmp.Compare(index, uint64(targetIndex))
+		if indexCmp != 0 {
+			return token, indexCmp
+		}
+
+		// If the index values are equivalent use the ID values
+		// as the comparison.
+		return token, cmp.Compare(id, targetParts[1])
 	}
 }
 

nomad/state/paginator/tokenizer_test.go

@@ -52,3 +52,94 @@ func TestTokenizer(t *testing.T) {
 		})
 	}
 }
+
+func TestCreateIndexAndIDTokenizer(t *testing.T) {
+	ci.Parallel(t)
+
+	cases := []struct {
+		name          string
+		obj           *mockCreateIndexObject
+		target        string
+		expectedToken string
+		expectedCmp   int
+	}{
+		{
+			name:          "common index (less)",
+			obj:           newMockCreateIndexObject(12, "aaa-bbb-ccc"),
+			target:        "12.bbb-ccc-ddd",
+			expectedToken: "12.aaa-bbb-ccc",
+			expectedCmp:   -1,
+		},
+		{
+			name:          "common index (greater)",
+			obj:           newMockCreateIndexObject(12, "bbb-ccc-ddd"),
+			target:        "12.aaa-bbb-ccc",
+			expectedToken: "12.bbb-ccc-ddd",
+			expectedCmp:   1,
+		},
+		{
+			name:          "common index (equal)",
+			obj:           newMockCreateIndexObject(12, "bbb-ccc-ddd"),
+			target:        "12.bbb-ccc-ddd",
+			expectedToken: "12.bbb-ccc-ddd",
+			expectedCmp:   0,
+		},
+		{
+			name:          "less index",
+			obj:           newMockCreateIndexObject(12, "aaa-bbb-ccc"),
+			target:        "89.aaa-bbb-ccc",
+			expectedToken: "12.aaa-bbb-ccc",
+			expectedCmp:   -1,
+		},
+		{
+			name:          "greater index",
+			obj:           newMockCreateIndexObject(89, "aaa-bbb-ccc"),
+			target:        "12.aaa-bbb-ccc",
+			expectedToken: "89.aaa-bbb-ccc",
+			expectedCmp:   1,
+		},
+		{
+			name:          "common index start (less)",
+			obj:           newMockCreateIndexObject(12, "aaa-bbb-ccc"),
+			target:        "102.aaa-bbb-ccc",
+			expectedToken: "12.aaa-bbb-ccc",
+			expectedCmp:   -1,
+		},
+		{
+			name:          "common index start (greater)",
+			obj:           newMockCreateIndexObject(102, "aaa-bbb-ccc"),
+			target:        "12.aaa-bbb-ccc",
+			expectedToken: "102.aaa-bbb-ccc",
+			expectedCmp:   1,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			fn := CreateIndexAndIDTokenizer[*mockCreateIndexObject](tc.target)
+			actualToken, actualCmp := fn(tc.obj)
+			must.Eq(t, tc.expectedToken, actualToken)
+			must.Eq(t, tc.expectedCmp, actualCmp)
+		})
+	}
+}
+
+func newMockCreateIndexObject(createIndex uint64, id string) *mockCreateIndexObject {
+	return &mockCreateIndexObject{
+		createIndex: createIndex,
+		id:          id,
+	}
+}
+
+type mockCreateIndexObject struct {
+	createIndex uint64
+	id          string
+}
+
+func (m *mockCreateIndexObject) GetCreateIndex() uint64 {
+	return m.createIndex
+}
+
+func (m *mockCreateIndexObject) GetID() string {
+	return m.id
+}