buildSolutionReferences with instance transformers

[gasnier]

Fixes #1025

I first tried a solution inspired from https://stackoverflow.com/questions/62026189/typescript-custom-transformers-with-ts-createwatchprogram/62132983#62132983
Where I used getNextInvalidatedProject from compiler api that is defined here :
https://github.com/microsoft/TypeScript/blob/master/src/compiler/tsbuildPublic.ts
This worked for standalone builds but was not working in watch mode.
In watch mode, it is SolutionBuilder that handles the emit and today there is no way to pass customTransformers to SolutionBuilder.

The final solution overrides the emit function and is based on https://github.com/nonara/ts-patch

[johnnyreilly]

Heads up, we've just renamed from master to main - https://twitter.com/johnny_reilly/status/1376156935414820869

This will have updated this PR but not your local branch. To apply there then:

git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a

[gasnier]

@johnnyreilly
This PR is ready for review

[johnnyreilly]

Thanks - I'll try and take a look this weekend

[johnnyreilly]

Sorry - I forgot about this. Just updated the branch. Will take a look.

[johnnyreilly]

Is transformers on instance now unused? If so, should it be removed?

https://github.com/gasnier/ts-loader/blob/6bb61d4088fcae03feca700e59f6e96c77f6244c/src/interfaces.ts#L212

[johnnyreilly]

Looking good I think. Two things:

• this PR is effectively working around the fact there is no way to pass customTransformers to SolutionBuilder. It would be good to raise that absence against the TypeScript project itself so they are aware of this. Perhaps in future a different approach could be used if something is implemented in TypeScript. Could you either link to the issue if it already exists, or raise it and link to it? Thanks. cc @sheetalkamat
• could you update package.json and CHANGELOG.md? Thanks!

[sheetalkamat]

This will have some bad effects .. emit is used for emitting dts files to determine shape of the file as well and take internal parameters and that signature is internal to typescript .. also I don’t think you want transformers for that reason ..

I have been thinking about your issue and was wondering if build could take getTransformers as function that returns transformers based on project path.. haven’t had chance to investigate that part yet but this approach is definitely not correct

[johnnyreilly]

Oh thanks for that @sheetalkamat - very helpful!

[gasnier]

Yes, if we can pass customTransformers to build in SolutionBuilder, this solves the problem.
the done function on invalidatedProject already has the customTransformers parameter.

A function by projet path is ok, anyway in ts-loader there is only one global configuration so we would always pass the same transformers. A good solution would be to do like ttypescript (https://github.com/cevek/ttypescript) and read the configuration from tsconfig.json

[sheetalkamat]

microsoft/TypeScript#43984 add the typescript side of the API

[johnnyreilly]

Should we close this now?

[gasnier]

Yes, I close it, I didn't know Typescript 4.3.1 was out...
Thanks @sheetalkamat

I will create another issue / PR to solve this using SolutionBuilder.