Backport #71949 to 24.9: Fix a crash in clickhouse-client syntax highlighting

src/Parsers/IParser.cpp

@@ -45,6 +45,16 @@ void Expected::highlight(HighlightedRange range)
         return;
 
     auto it = highlights.lower_bound(range);
+
+    /// Highlights are sorted by their starting position.
+    /// lower_bound(range) will find the first highlight where begin >= range.begin.
+    /// However, this does not ensure that the previous highlight's end <= range.begin.
+    /// By checking the previous highlight, if it exists, we ensure that
+    /// for each highlight x and the next one y: x.end <= y.begin, thus preventing any overlap.
+
+    if (it != highlights.begin())
+        it = std::prev(it);
+
     while (it != highlights.end() && range.begin < it->end)
     {
         if (intersects(range.begin, range.end, it->begin, it->end))

tests/queries/0_stateless/03272_client_highlighting_bug.expect

@@ -0,0 +1,39 @@
+#!/usr/bin/expect -f
+
+set basedir [file dirname $argv0]
+set basename [file tail $argv0]
+if {[info exists env(CLICKHOUSE_TMP)]} {
+    set CLICKHOUSE_TMP $env(CLICKHOUSE_TMP)
+} else {
+    set CLICKHOUSE_TMP "."
+}
+exp_internal -f $CLICKHOUSE_TMP/$basename.debuglog 0
+set history_file $CLICKHOUSE_TMP/$basename.history
+
+log_user 0
+set timeout 60
+match_max 100000
+
+expect_after {
+    # Do not ignore eof from expect
+    -i $any_spawn_id eof { exp_continue }
+    # A default timeout action is to do nothing, change it to fail
+    -i $any_spawn_id timeout { exit 1 }
+}
+
+spawn bash -c "source $basedir/../shell_config.sh ; \$CLICKHOUSE_CLIENT_BINARY \$CLICKHOUSE_CLIENT_OPT --disable_suggestion --enable-progress-table-toggle=0 --history_file=$history_file"
+
+# (?n) - Do not match new lines
+expect -re "(?n)ClickHouse client version \[\\d\]{2}\.\[\\d\]{1,2}\.\[\\d\]{1,2}\.\[\\d\]{1,}.*\r"
+expect -re "(?n)Connecting to database .* at localhost:9000 as user default\.\r"
+expect -re "(?n)Connected to ClickHouse server version \[\\d\]{2}\.\[\\d\]{1,2}\.\[\\d\]{1,2}\.\r"
+expect ":) "
+
+send -- "SELECT (+123) AS x"
+expect {SELECT (+1) AS x}
+
+send -- "\r"
+expect ":) "
+
+send -- ""
+expect eof