qt_add_lupdate() won't generate "*.ts" files unless there already exist.

According to the Documentation, qt_add_lupdate() should automatically create *.ts files if there doesn't exist originally. Am I right?

Add targets to generate or update Qt Linguist .ts files

However, it didn't work as I thought. The *.ts files won't be generated if there doesn't exist.

After some experiments, I found that I have to do the following steps:

1. Create some empty *.ts files (zh_TW.ts and zh_CN.ts).
2. Configure and Execute the custom target ${target}_lupdate.
   It will definitely show errors of parsing. For example:

   [build] Parse error at D:/Code-Cpp-MyFavorite/Code-CMake-Qt-LiNing/source/15-International/ts/zh_TW.ts:1:0: Premature end of document.

1. Delete those empty *.ts files (zh_TW.ts and zh_CN.ts).
2. Configure and Execute the custom target ${target}_lupdate.
   This time, it works. For example:

   [build] Updating '../../../../source/15-International/ts/zh_TW.ts'...
   [build]     Found 7 source text(s) (7 new and 0 already existing)

GIF of Experiments