CLI: Do not use modern TS assets in legacy TS projects

[IanVS]

Issue:

New TypeScript (4.9+) syntax components could be added to a project using an older version of TS, if the renderer did not include a ts-legacy folder.

What I did

Removed that unsafe fallback, and added some tests.

How to test

• Is this testable with Jest or Chromatic screenshots?
• Does this need a new example in the kitchen sink apps?
• Does this need an update to the documentation?

If your answer is yes to any of these, please make sure to include it in your PR.

[shilman]

LGTM, @kasperpeulen can you please take a look?

[kasperpeulen]

@shilman @IanVS I think this will break angular and web components, as they have only a ts directory, as there is no special syntax for TS4.9 for those renderers. I didnt want to duplicate directories there.

I think we may just have to be careful to always have a ts-legacy directory when there is a ts directory with new ts features.

[IanVS]

In that situation wouldn't it be better to name the folder ts-legacy? Then it would still be used by both, without the danger of breaking if someone creates just a new ts directory like almost just happened for Vue?

[kasperpeulen]

In that situation wouldn't it be better to name the folder ts-legacy? Then it would still be used by both, without the danger of breaking if someone creates just a new ts directory like almost just happened for Vue?

Yeah, I understand that point, but there may never come a ts directory for angular, as I think it might be imposible to ever take adventage of satisfies there. So it would be also a bit weird to only having ts-legacy in the renderer, while we use it also for modern ts. 🤔

[IanVS]

Thanks for explaining. I personally still think it's better to be safe and have an awkward folder name for Angular, or use a different word than legacy if that's the issue. Do we have any tests that will detect if 4.9 syntax is used in a ts folder, without a ts-legacy? This will break for users, which IMHO we should be careful to avoid.

[kasperpeulen]

@IanVS Hmm, I would say the correct approach would be to never have "only" have a ts directory if it contains TS>=4.9 code. In that scenario, you always want to have also a ts-legacy directory, otherwise we will fallback to js in a ts project.

I guess the approach of this PR is more safe, but not sure if it is more "right" :D

Say someone makes a PR that would add a ts directory to a renderer, but not taking advantage of TS 4.9 features, when we merge such a PR, it would only install use the ts directory for TS >= 4.9 projects, and fall back to JS in TS<4.9 projects, which is not what someone would expect I guess.

If we force such the ts-legacy directory name for renderers such angular and web-components, it may look weird, and people might think, hey the ts directory is missing, while that directory would not make sense.

Anyway, I understand your point as well. What do you think @shilman ?

[shilman]

@kasperpeulen @IanVS I agree with both of you. I think the ideal approach would be to have the minimum version of TS that we require embedded in the directory name. So we could rename existing ts-legacy to ts-3-0 (or whatever "legacy" is currently an alias for) and the ts to ts-4-9. That way if, for some reason a user has a "TS 2.9" project it would fall back to JS (and perhaps yell at the user with the required explanation), which is weird but perhaps the right thing to do. WDYT?

[IanVS]

Yep, I like that approach.

[IanVS]

Marking as draft until I make the suggested change.

[IanVS]

The minimum TS version for our current examples is 3.8, because we use import type.

[IanVS]

@kasperpeulen what do you think of this now?

[kasperpeulen]

LGTM!!