Cherry pick of a06d506 (#35172) into release-10.11 (#35332)

Automatic Merge

server/public/utils/page.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package utils
+
+// Pager fetches all items from a paginated API.
+// Pager is a generic function that fetches and aggregates paginated data.
+// It takes a fetch function and a perPage parameter as arguments.
+//
+// The fetch function is responsible for retrieving a slice of items of type T
+// for a given page number. It returns the fetched items and an error, if any.
+// Ideally a developer may want to use a closure to create a fetch function.
+//
+// The perPage parameter specifies the number of items to fetch per page.
+//
+// Example usage:
+//
+//	items, err := Pager(fetchFunc, 10)
+//	if err != nil {
+//	    // handle error
+//	}
+//	// process items
+func Pager[T any](fetch func(page int) ([]T, error), perPage int) ([]T, error) {
+	var list []T
+	var page int
+
+	for {
+		fetched, err := fetch(page)
+		if err != nil {
+			return list, err
+		}
+
+		list = append(list, fetched...)
+
+		if len(fetched) < perPage {
+			break
+		}
+
+		page++
+	}
+
+	return list, nil
+}

server/public/utils/page_test.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package utils
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPager(t *testing.T) {
+	tests := []struct {
+		name      string
+		fetch     func(page int) ([]int, error)
+		perPage   int
+		expected  []int
+		expectErr bool
+	}{
+		{
+			name: "successful fetch",
+			fetch: func(page int) ([]int, error) {
+				if page > 2 {
+					return nil, nil
+				}
+				return []int{page*10 + 1, page*10 + 2, page*10 + 3}, nil
+			},
+			perPage:  3,
+			expected: []int{1, 2, 3, 11, 12, 13, 21, 22, 23},
+		},
+		{
+			name: "fetch with error",
+			fetch: func(page int) ([]int, error) {
+				if page == 1 {
+					return nil, errors.New("fetch error")
+				}
+				return []int{page*10 + 1, page*10 + 2, page*10 + 3}, nil
+			},
+			perPage:   3,
+			expected:  []int{1, 2, 3},
+			expectErr: true,
+		},
+		{
+			name: "fetch with fewer items than perPage",
+			fetch: func(page int) ([]int, error) {
+				if page > 0 {
+					return []int{11, 12}, nil
+				}
+				return []int{page*10 + 1, page*10 + 2, page*10 + 3}, nil
+			},
+			perPage:  3,
+			expected: []int{1, 2, 3, 11, 12},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := Pager(tt.fetch, tt.perPage)
+			if tt.expectErr {
+				assert.Error(t, err)
+				assert.Equal(t, tt.expected, result)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.expected, result)
+			}
+		})
+	}
+}