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// Copyright 2016 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package iterator_test
import (
"encoding/json"
"math"
"reflect"
"testing"
"golang.org/x/net/context"
"google.golang.org/api/iterator"
itest "google.golang.org/api/iterator/testing"
)
// Service represents the implementation of a Google API's List method.
// We want to test against a large range of possible valid behaviors.
// All the behaviors this can generate are valid under the spec for
// Google API paging.
type service struct {
// End of the sequence. end-1 is the last value returned.
end int
// Maximum number of items to return in one RPC. Also the default page size.
// If zero, max is unlimited.
max int
// If true, return two empty pages before each RPC that returns items, and
// two zero pages at the end. E.g. if end = 5, max = 2 and the pageSize
// parameter to List is zero, then the number of items returned in
// successive RPCS is:
// 0 0 2 0 0 2 0 0 1 0 0
// Note that this implies that the RPC returning the last items will have a
// non-empty page token.
zeroes bool
}
// List simulates an API List RPC. It returns integers in the range [0, s.end).
func (s *service) List(pageSize int, pageToken string) ([]int, string, error) {
max := s.max
if max == 0 {
max = math.MaxInt64
}
// Never give back any more than s.max.
if pageSize <= 0 || pageSize > max {
pageSize = max
}
state := &listState{}
if pageToken != "" {
if err := json.Unmarshal([]byte(pageToken), state); err != nil {
return nil, "", err
}
}
ints := state.advance(pageSize, s.end, s.zeroes)
if state.Start == s.end && (!s.zeroes || state.NumZeroes == 2) {
pageToken = ""
} else {
bytes, err := json.Marshal(state)
if err != nil {
return nil, "", err
}
pageToken = string(bytes)
}
return ints, pageToken, nil
}
type listState struct {
Start int // where to start this page
NumZeroes int // number of consecutive empty pages before this
}
func (s *listState) advance(pageSize, end int, zeroes bool) []int {
var page []int
if zeroes && s.NumZeroes != 2 {
// Return a zero page.
} else {
for i := s.Start; i < end && len(page) < pageSize; i++ {
page = append(page, i)
}
}
s.Start += len(page)
if len(page) == 0 {
s.NumZeroes++
} else {
s.NumZeroes = 0
}
return page
}
func TestServiceList(t *testing.T) {
for _, test := range []struct {
svc service
pageSize int
want [][]int
}{
{service{end: 0}, 0, [][]int{nil}},
{service{end: 5}, 0, [][]int{{0, 1, 2, 3, 4}}},
{service{end: 5}, 8, [][]int{{0, 1, 2, 3, 4}}},
{service{end: 5}, 2, [][]int{{0, 1}, {2, 3}, {4}}},
{service{end: 5, max: 2}, 0, [][]int{{0, 1}, {2, 3}, {4}}},
{service{end: 5, max: 2}, 1, [][]int{{0}, {1}, {2}, {3}, {4}}},
{service{end: 5, max: 2}, 10, [][]int{{0, 1}, {2, 3}, {4}}},
{service{end: 5, zeroes: true}, 0, [][]int{nil, nil, {0, 1, 2, 3, 4}, nil, nil}},
{service{end: 5, max: 3, zeroes: true}, 0, [][]int{nil, nil, {0, 1, 2}, nil, nil, {3, 4}, nil, nil}},
} {
var got [][]int
token := ""
for {
items, nextToken, err := test.svc.List(test.pageSize, token)
if err != nil {
t.Fatalf("%v, %d: %v", test.svc, test.pageSize, err)
}
got = append(got, items)
if nextToken == "" {
break
}
token = nextToken
}
if !reflect.DeepEqual(got, test.want) {
t.Errorf("%v, %d: got %v, want %v", test.svc, test.pageSize, got, test.want)
}
}
}
type Client struct{ s *service }
// ItemIterator is a sample implementation of a standard iterator.
type ItemIterator struct {
pageInfo *iterator.PageInfo
nextFunc func() error
s *service
items []int
}
// PageInfo returns a PageInfo, which supports pagination.
func (it *ItemIterator) PageInfo() *iterator.PageInfo { return it.pageInfo }
// Items is a sample implementation of an iterator-creating method.
func (c *Client) Items(ctx context.Context) *ItemIterator {
it := &ItemIterator{s: c.s}
it.pageInfo, it.nextFunc = iterator.NewPageInfo(
it.fetch,
func() int { return len(it.items) },
func() interface{} { b := it.items; it.items = nil; return b })
return it
}
func (it *ItemIterator) fetch(pageSize int, pageToken string) (string, error) {
items, tok, err := it.s.List(pageSize, pageToken)
it.items = append(it.items, items...)
return tok, err
}
func (it *ItemIterator) Next() (int, error) {
if err := it.nextFunc(); err != nil {
return 0, err
}
item := it.items[0]
it.items = it.items[1:]
return item, nil
}
func TestNext(t *testing.T) {
// Test the iterator's Next method with a variety of different service behaviors.
// This is primarily a test of PageInfo.next.
for _, svc := range []service{
{end: 0},
{end: 5},
{end: 5, max: 1},
{end: 5, max: 2},
{end: 5, zeroes: true},
{end: 5, max: 2, zeroes: true},
} {
client := &Client{&svc}
msg, ok := itest.TestIterator(
seq(0, svc.end),
func() interface{} { return client.Items(ctx) },
func(it interface{}) (interface{}, error) { return it.(*ItemIterator).Next() })
if !ok {
t.Errorf("%+v: %s", svc, msg)
}
}
}
// TODO(jba): test setting PageInfo.MaxSize
// TODO(jba): test setting PageInfo.Token
// Verify that, for an iterator that uses PageInfo.next to implement its Next
// method, using Next and NextPage together result in an error.
func TestNextWithNextPage(t *testing.T) {
client := &Client{&service{end: 11}}
var items []int
// Calling Next before NextPage.
it := client.Items(ctx)
it.Next()
_, err := iterator.NewPager(it, 1, "").NextPage(&items)
if err == nil {
t.Error("NextPage after Next: got nil, want error")
}
_, err = it.Next()
if err == nil {
t.Error("Next after NextPage: got nil, want error")
}
// Next between two calls to NextPage.
it = client.Items(ctx)
p := iterator.NewPager(it, 1, "")
p.NextPage(&items)
_, err = it.Next()
if err == nil {
t.Error("Next after NextPage: got nil, want error")
}
_, err = p.NextPage(&items)
if err == nil {
t.Error("second NextPage after Next: got nil, want error")
}
}
// Verify that we turn various potential reflection panics into errors.
func TestNextPageReflectionErrors(t *testing.T) {
client := &Client{&service{end: 1}}
p := iterator.NewPager(client.Items(ctx), 1, "")
// Passing the nil interface value.
_, err := p.NextPage(nil)
if err == nil {
t.Error("nil: got nil, want error")
}
// Passing a non-slice.
_, err = p.NextPage(17)
if err == nil {
t.Error("non-slice: got nil, want error")
}
// Passing a slice of the wrong type.
var bools []bool
_, err = p.NextPage(&bools)
if err == nil {
t.Error("wrong type: got nil, want error")
}
// Using a slice of the right type, but not passing a pointer to it.
var ints []int
_, err = p.NextPage(ints)
if err == nil {
t.Error("not a pointer: got nil, want error")
}
}
// seq returns a slice containing the values in [from, to).
func seq(from, to int) []int {
var r []int
for i := from; i < to; i++ {
r = append(r, i)
}
return r
}
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