tests: add a test for clickhouse-client autocompletion

v2: Increase timeout for 01676_clickhouse_client_autocomplete
    https://github.com/ClickHouse/ClickHouse/pull/19584#discussion_r565727175

v3: Disable 01676_clickhouse_client_autocomplete in unbundled build (arcadia)

    autocomplete does not have to work fully unbundled build (since it lack
    of replxx).

    Similar to bd523a0aff

v4: set expect timeout back to 1 and increase total timeout to 20 sec
v4: set expect timeout back to 3 and increase total timeout to 22 (3*X+1) sec

programs/client/Suggest.cpp

@@ -87,6 +87,11 @@ Suggest::Suggest()
 
 void Suggest::loadImpl(Connection & connection, const ConnectionTimeouts & timeouts, size_t suggestion_limit)
 {
+    ///
+    /// NOTE: Once you will update the completion list,
+    /// do not forget to update 01676_clickhouse_client_autocomplete.sh
+    ///
+
     std::stringstream query;        // STYLE_CHECK_ALLOW_STD_STRING_STREAM
     query << "SELECT DISTINCT arrayJoin(extractAll(name, '[\\\\w_]{2,}')) AS res FROM ("
         "SELECT name FROM system.functions"

tests/queries/0_stateless/01676_clickhouse_client_autocomplete.sh

@@ -0,0 +1,114 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+function test_completion_word()
+{
+    local w=$1 && shift
+
+    local w_len=${#w}
+    local compword_begin=${w:0:$((w_len-3))}
+    local compword_end=${w:$((w_len-3))}
+
+    # NOTE: here and below you should escape variables of the expect.
+    timeout 22s expect << EOF
+log_user 0
+set timeout 3
+match_max 100000
+# A default timeout action is to do nothing, change it to fail
+expect_after {
+    timeout {
+        exit 1
+    }
+}
+
+spawn bash -c "$CLICKHOUSE_CLIENT_BINARY $CLICKHOUSE_CLIENT_OPT"
+expect ":) "
+
+# Make a query
+send -- "SET $compword_begin"
+expect "SET $compword_begin"
+
+# Wait for suggestions to load, they are loaded in background
+set is_done 0
+while {\$is_done == 0} {
+    send -- "\\t"
+    expect {
+        "$compword_begin$compword_end" {
+            set is_done 1
+        }
+        default {
+            sleep 1
+        }
+    }
+}
+
+send -- "\\3\\4"
+expect eof
+EOF
+}
+
+# last 3 bytes will be completed,
+# so take this in mind when you will update the list.
+compwords_positive=(
+    # system.functions
+    concatAssumeInjective
+    # system.table_engines
+    ReplacingMergeTree
+    # system.formats
+    JSONEachRow
+    # system.table_functions
+    clusterAllReplicas
+    # system.data_type_families
+    SimpleAggregateFunction
+    # system.merge_tree_settings
+    write_ahead_log_interval_ms_to_fsync
+    # system.settings
+    max_concurrent_queries_for_all_users
+    # system.clusters
+    test_shard_localhost
+    # system.errors, also it is very rare to cover system_events_show_zero_values
+    CONDITIONAL_TREE_PARENT_NOT_FOUND
+    # system.events, also it is very rare to cover system_events_show_zero_values
+    WriteBufferFromFileDescriptorWriteFailed
+    # system.asynchronous_metrics, also this metric has zero value
+    #
+    # NOTE: that there is no ability to complete metrics like
+    # jemalloc.background_thread.num_runs, due to "." is used as a word breaker
+    # (and this cannot be changed -- db.table)
+    ReplicasMaxAbsoluteDelay
+    # system.metrics
+    PartsPreCommitted
+    # system.macros
+    default_path_test
+    # system.storage_policies, egh not uniq
+    default
+    # system.aggregate_function_combinators
+    uniqCombined64ForEach
+
+    # FIXME: one may add separate case for suggestion_limit
+    # system.databases
+    system
+    # system.tables
+    aggregate_function_combinators
+    # system.columns
+    primary_key_bytes_in_memory_allocated
+    # system.dictionaries
+    # FIXME: none
+)
+for w in "${compwords_positive[@]}"; do
+    test_completion_word "$w" || echo "[FAIL] $w (positive)"
+done
+
+# One negative is enough
+compwords_negative=(
+    # system.clusters
+    test_shard_localhost_no_such_cluster
+)
+for w in "${compwords_negative[@]}"; do
+    test_completion_word "$w" && echo "[FAIL] $w (negative)"
+done
+
+exit 0

tests/queries/0_stateless/arcadia_skip_list.txt

@@ -198,3 +198,4 @@
 01659_test_base64Decode_mysql_compatibility
 01675_data_type_coroutine
 01671_aggregate_function_group_bitmap_data
+01676_clickhouse_client_autocomplete

tests/queries/skip_list.json

@@ -90,6 +90,7 @@
         "01300_client_save_history_when_terminated",
         "orc_output",
         "01370_client_autocomplete_word_break_characters",
+        "01676_clickhouse_client_autocomplete",
         "01193_metadata_loading",
         "01455_time_zones"
     ],