I was wondering if the new lockfileVersion 2 was backwards compatable with older versions of NPM.
Now since NPM 7 is released, a new package-lock.json file is regenerated to a different structure. From lockfileVersion 1 to 2.
I would be guessing if it was supported, if adding new packages from old npm lockfile to the new one would not be compatible.
Yes it is, I tried it myself. And here's a remark from the blog:
One change to take note of is the new lockfile format, which is backwards compatible with npm 6 users.
source: https://github.blog/2021-02-02-npm-7-is-now-generally-available/#changes-to-the-lockfile