Move typescript to a peer dependency

[wagenet]

This will allow the version of typescript to be determined by whoever is using this.

[chriskrycho]

My suggestion (which I already suggested to @wagenet in a Discord DM, just noting here for posterity): go ahead and move TS to peerDependencies, as here, but also add a supported range of TS versions in CI.

[wagenet]

Unfortunately, I'm not sure how to fix these test failures.

[SergeAstapov]

@wagenet I may be wrong, but this not gonna make any difference as still will install typescript@4.0.3 by npm 7+

It's technically the same as replacing "typescript": "~4.0.3" with "typescript": "^4.0.3".

To truly decouple typescript version from broccoli-typescript-compiler, maybe you meant to make this

"peerDependencies": {
    "typescript": "*"
},
"peerDependenciesMeta": {
  "typescript": {
    "optional": true
  }
},

[wagenet]

@SergeAstapov ah, you may be correct.

[wagenet]

My understanding is that this means that, if a newer compatible version is installed, it will use that one. So this should be correct. I've been having some trouble validating it in practice either way.

[chancancode]

Can we assert that TypeScript is actually installed (with require.resolve maybe?) and that it actually matches the semver range we asked for, since peer dependencies are just a "recommendation" in multiple versions of NPM? (It would have failed anyway, but we can give a nicer error message)

Otherwise looks good

[chancancode]

This probably needs to be a breaking change since you automatically get typescript from having this package before, and that no longer happens after this change. (Probably should update the install instructions as well)

[wagenet]

@chancancode sounds good.