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fix(common): pagination must support empty pages #11937

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merged 2 commits into from
Jun 22, 2023
Merged

fix(common): pagination must support empty pages #11937

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6e25625
fix(common): pagination must support empty pages
coryan Jun 21, 2023
b5ab140
Address review comments
coryan Jun 22, 2023
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5 changes: 2 additions & 3 deletions google/cloud/internal/pagination_range.h
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Original file line number Diff line number Diff line change
Expand Up @@ -93,17 +93,16 @@ class PagedStreamReader {
* successful end of stream.
*/
typename StreamReader<T>::result_type GetNext() {
if (current_ == page_.end()) {
if (last_page_) return Status{};
while (current_ == page_.end() && !last_page_) {
request_.set_page_token(std::move(token_));
auto response = loader_(request_);
if (!response.ok()) return std::move(response).status();
token_ = ExtractPageToken(*response);
if (token_.empty()) last_page_ = true;
page_ = extractor_(*std::move(response));
current_ = page_.begin();
if (current_ == page_.end()) return Status{};
}
if (current_ == page_.end()) return Status{};
return std::move(*current_++);
}

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57 changes: 57 additions & 0 deletions google/cloud/internal/pagination_range_test.cc
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Expand Up @@ -197,6 +197,63 @@ TYPED_TEST(PaginationRangeTest, TwoPages) {
EXPECT_THAT(names, ElementsAre("p1", "p2", "p3", "p4"));
}

TYPED_TEST(PaginationRangeTest, EmptyAndFullPages) {
using ResponseType = TypeParam;
MockRpc<ResponseType> mock;
EXPECT_CALL(mock, Loader)
.WillOnce([](Request const& request) {
EXPECT_EQ(CurrentOptions().get<StringOption>(), "EmptyAndFullPages");
EXPECT_TRUE(request.testonly_page_token.empty());
ResponseType response;
response.testonly_set_page_token("t1");
return response;
})
.WillOnce([](Request const& request) {
EXPECT_EQ(CurrentOptions().get<StringOption>(), "EmptyAndFullPages");
EXPECT_EQ("t1", request.testonly_page_token);
ResponseType response;
response.testonly_set_page_token("t2");
return response;
})
.WillOnce([](Request const& request) {
EXPECT_EQ(CurrentOptions().get<StringOption>(), "EmptyAndFullPages");
EXPECT_EQ("t2", request.testonly_page_token);
ResponseType response;
response.testonly_items.push_back(Item{"p1"});
response.testonly_items.push_back(Item{"p2"});
response.testonly_set_page_token("t3");
return response;
})
.WillOnce([](Request const& request) {
EXPECT_EQ(CurrentOptions().get<StringOption>(), "EmptyAndFullPages");
EXPECT_EQ("t3", request.testonly_page_token);
ResponseType response;
response.testonly_set_page_token("t4");
return response;
})
.WillOnce([](Request const& request) {
EXPECT_EQ(CurrentOptions().get<StringOption>(), "EmptyAndFullPages");
EXPECT_EQ("t4", request.testonly_page_token);
ResponseType response;
response.testonly_items.push_back(Item{"p3"});
response.testonly_items.push_back(Item{"p4"});
response.testonly_set_page_token("");
return response;
});

OptionsSpan span(Options{}.set<StringOption>("EmptyAndFullPages"));
auto range = MakePaginationRange<ItemRange>(
Request{}, [&mock](Request const& r) { return mock.Loader(r); },
[](ResponseType const& r) { return r.testonly_items; });
OptionsSpan overlay(Options{}.set<StringOption>("uh-oh"));
std::vector<std::string> names;
for (auto& p : range) {
if (!p) break;
names.push_back(p->data);
}
EXPECT_THAT(names, ElementsAre("p1", "p2", "p3", "p4"));
}

TYPED_TEST(PaginationRangeTest, TwoPagesWithError) {
using ResponseType = TypeParam;
MockRpc<ResponseType> mock;
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