Document reason for TS 2.7 support, possibly increase minimum supported version

[cspotcode]

When I started working on ts-node, the readme said we supported TS 2.7 and the tests ran against TS 2.7, so I've maintained that support. But I don't actually know why we support that version. Enough time has passed, it may make sense to increase the minimum supported version.

@blakeembrey do you remember if there were any specific reasons for supporting 2.7? Was a high-profile project stuck on 2.7 at some point in the past?

A quick search turned up #527 but I don't know if it's related.

Some data points:

• ts playground supports as far back as 3.3.3 https://www.typescriptlang.org/play
• DefinitelyTyped tests TS versions less than 2 years old. Currently 3.5 and above https://github.com/DefinitelyTyped/DefinitelyTyped#older-versions-of-typescript-34-and-earlier
• typescript 2.7 does not support the lib options in @tsconfig/node12 from @tsconfig/bases

[cspotcode]

Or maybe ts-node added a feature that could not work on versions older than 2.7, and so it was documented that 2.7 was the minimum?

[blakeembrey]

Yeah, if you need to upgrade in a major version don't restrict yourself! I don't really remember now, but going a git blame on that specific line in the README is pretty helpful for the history of the changes. Looks like I last bumped it from 2.0 -> 2.7 in #895 which was a minimum feature requirement.

[cspotcode]

Ok, thanks. Turns out it won't be necessary for v10, because I ended up re-adding @tsconfig/node10 to keep things simple. But this is good to know for v11.

[cspotcode]

Closing as answered.

[jhmaster2000]

To future readers, as the milestone links above aren't very helpful to connect these together, the v11 plan relating to this issue is here: #1505