Lock normalization doesn't persist across updates

Describe the problem as clearly as you can

In this doc, it's mentioned that one should call normalize-lock before add-checksums.

https://bundler.io/blog/2024/12/19/bundler-v2-6.html#:~:text=Should%20I%20take%20any%20other%20steps%20before%20enabling%20this%20feature%3F

Which works great. However, if a gem in a new version adds new platforms, the bundle install doesn't renormalize, so you end up out of sync again.

Did you try upgrading rubygems & bundler?

Yes, on latest of both (2.6.3)

Post steps to reproduce the problem

Gemfile to start:

# frozen_string_literal: true

source 'https://rubygems.org'

gem 'nokogiri', '1.16.7'

Then run the following:

• bundle install; bundle lock --add-platform ruby; bundle lock --normalize-platforms; bundle lock --add-checksums
• commit those into git.
• update nokogiri in the Gemfile turning that into:

# frozen_string_literal: true

source 'https://rubygems.org'

gem 'nokogiri', '1.18.2'

• run bundle install
• commit that into git
• then run bundle lock --normalize-platforms

Notice the lock is now now changed as new platforms were added by nokogiri, but not auto-added to the lock.

Which command did you run?

See above

What were you expecting to happen?

Once you normalize once per docs, it is kept up to date automatically (especially to avoid running into https://github.com/rubygems/rubygems/issues/8391 if someone installs from a different platform but already had

What actually happened?

New gem platforms were not auto-added to the lock

Start with the Bundler lock workflow exercised by the reported commands, using the Gemfile and lockfile from the nokogiri 1.16.7 to 1.18.2 reproduction. Run bundle install, bundle lock --normalize-platforms, and the other listed lock commands; done means newly introduced gem platforms are automatically included after updates.