Incorrectly Formatted Packages in --moduleResolution bundler/node16

#51973

• Test to see what breaks if node is redirected to bundler.
• Previously types would have been resolved.
  • Now the exports.import condition is resolved as per Node 16 rules.
• Now providing a better error message when we can detect this. You'd get the same error in node16.
  • The messages are still bad because we provide an absolute path to the file instead of a relative path.
  • Presumably we did this because the relative path isn't the correct thing when printing paths in the command line.
• Aside: would be good to do the same tests for redirecting node16/nodenext

LKG versus node_modules

• ESLint relies on node_modules, our builds rely on LKG builds in lib.
• Would be nice if they could agree with each other!
• Would also be nice to get rid of lib and use npm for boostrapping.
  • But then people can't clone TypeScript and just run from lib.
  • But we could just do that on release branches anyway.
• Not great to snapshot 40MB of JS on every LKG!
  • Git doesn't store that as a diff!
  • Cloning takes a while these days
    • Though there are ways to make this easier: https://github.blog/2020-12-21-get-up-to-speed-with-partial-clone-and-shallow-clone/
• So switch to nightlies on npm instead of building from lib?
  • Have to always npm ci on git pull
  • Technically true today, but it's rare that that even makes a difference. So you can get away with it.
  • But it would also be rare for us too. How often do we update LKG?
  • EXCEPT you still need to when you're bisecting!
    • Ugh - annoying. But might be worth it long term.
• Edge case - ESLint looks at the current package typescript/ instead of the typescript/node_modules/typescript.
  • Follow up on if this is true.
• So
  • Switch to using npm and node_modules
  • Delete lib
  • lib gets .gitignore'd
  • We force-add lib on release-X.Y branches and commit it.
  • lib gets published on npm.
  • When we need to take advantage of a new feature sooner than the same day, we can publish an insiders or early nightly instead.