What is the no source mean?

[lanmch]

recently, we change our npm manager, but i found that the no source increase too much, maybe every chunk +100~200KB, but I dont know how to find the real code which should not be added.
hope for help

[nikolay-borzov]

From the README

Mapped code without source. It might be code generated by a bundler (e.g. webpack). Represented by [no source] in explore result.

It means there are record that don't have the source set (source man doesn't say to from which file the code came)