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CDRIVER-5515 fix assert when legacy exhaust cursor receives no documents #1562

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Merged
merged 2 commits into from
Apr 2, 2024
Merged

CDRIVER-5515 fix assert when legacy exhaust cursor receives no documents #1562

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03dc94a
add regression test
kevinAlbs Mar 25, 2024
d077ad9
CDRIVER-5515 handle NULL for OP_REPLY documents
kevinAlbs Mar 25, 2024
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20 changes: 16 additions & 4 deletions src/libmongoc/src/mongoc/mongoc-cursor-legacy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -222,8 +222,14 @@ _mongoc_cursor_op_getmore (mongoc_cursor_t *cursor, mongoc_cursor_response_legac

cursor->cursor_id = mcd_rpc_op_reply_get_cursor_id (response->rpc);

response->reader = bson_reader_new_from_data (mcd_rpc_op_reply_get_documents (response->rpc),
mcd_rpc_op_reply_get_documents_len (response->rpc));
const void *documents = mcd_rpc_op_reply_get_documents (response->rpc);
if (documents == NULL) {
// Use a non-NULL pointer to satisfy precondition of
// `bson_reader_new_from_data`:
documents = "";
}

response->reader = bson_reader_new_from_data (documents, mcd_rpc_op_reply_get_documents_len (response->rpc));

_mongoc_cursor_monitor_succeeded (cursor,
response,
Expand Down Expand Up @@ -584,8 +590,14 @@ _mongoc_cursor_op_query_find (mongoc_cursor_t *cursor, bson_t *filter, mongoc_cu

cursor->cursor_id = mcd_rpc_op_reply_get_cursor_id (response->rpc);

response->reader = bson_reader_new_from_data (mcd_rpc_op_reply_get_documents (response->rpc),
mcd_rpc_op_reply_get_documents_len (response->rpc));
const void *documents = mcd_rpc_op_reply_get_documents (response->rpc);
if (documents == NULL) {
// Use a non-NULL pointer to satisfy precondition of
// `bson_reader_new_from_data`:
documents = "";
}

response->reader = bson_reader_new_from_data (documents, mcd_rpc_op_reply_get_documents_len (response->rpc));

if (_mongoc_cursor_get_opt_bool (cursor, MONGOC_CURSOR_EXHAUST)) {
cursor->in_exhaust = true;
Expand Down
41 changes: 41 additions & 0 deletions src/libmongoc/tests/test-mongoc-exhaust.c
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Original file line number Diff line number Diff line change
Expand Up @@ -345,6 +345,45 @@ test_exhaust_cursor_works (void *context)
mongoc_client_destroy (client);
}

// `test_exhaust_cursor_no_match` is a regression test for CDRIVER-5515
static void
test_exhaust_cursor_no_match (void *context)
{
BSON_UNUSED (context);
bson_error_t error;
mongoc_client_t *client = test_framework_new_default_client ();
mongoc_collection_t *coll = mongoc_client_get_collection (client, "db", "coll");

// Drop collection to remove prior test data.
mongoc_collection_drop (coll, NULL /* ignore error */);

mongoc_cursor_t *cursor =
mongoc_collection_find_with_opts (coll, tmp_bson ("{}"), tmp_bson ("{'exhaust': true }"), NULL /* read_prefs */);
const bson_t *result;
size_t count = 0;
while (mongoc_cursor_next (cursor, &result)) {
count++;
}
// Expect an error if exhaust cursors are not supported.
const bool sharded = _mongoc_topology_get_type (cursor->client->topology) == MONGOC_TOPOLOGY_SHARDED;
int64_t wire_version;
test_framework_get_max_wire_version (&wire_version);
if (sharded && wire_version < WIRE_VERSION_MONGOS_EXHAUST) {
ASSERT (mongoc_cursor_error (cursor, &error));
ASSERT_ERROR_CONTAINS (error, MONGOC_ERROR_CURSOR, MONGOC_ERROR_CURSOR_INVALID_CURSOR, "exhaust cursors require");
} else {
// Expect no error.
ASSERT_OR_PRINT (!mongoc_cursor_error (cursor, &error), error);
// Expect no results.
ASSERT_CMPSIZE_T (count, ==, 0);
}

mongoc_cursor_destroy (cursor);
mongoc_collection_destroy (coll);
mongoc_client_destroy (client);
}


static void
test_exhaust_cursor_single (void *context)
{
Expand Down Expand Up @@ -709,6 +748,8 @@ void
test_exhaust_install (TestSuite *suite)
{
TestSuite_AddFull (suite, "/Client/exhaust_cursor/works", test_exhaust_cursor_works, NULL, NULL, skip_if_no_exhaust);
TestSuite_AddFull (
suite, "/Client/exhaust_cursor/no_match", test_exhaust_cursor_no_match, NULL, NULL, skip_if_no_exhaust);
TestSuite_AddFull (
suite, "/Client/exhaust_cursor/single", test_exhaust_cursor_single, NULL, NULL, skip_if_no_exhaust);
TestSuite_AddFull (suite, "/Client/exhaust_cursor/pool", test_exhaust_cursor_pool, NULL, NULL, skip_if_no_exhaust);
Expand Down