Support for configuration inheritance

[mihe]

The new extends setting in tsconfig (microsoft/TypeScript#9876) doesn't seem to be supported by gulp-typescript (3.1.3). If I compile through gulp-typescript using a tsconfig that utilizes said setting, it seems to simply behave as if the inherited settings are simply missing and uses the default values instead.

[ivogabe]

Thanks for posting, I wasn't aware of that. I think/hope that the TypeScript API exports some functions for this. Can you try to create a pull request? Otherwise I'll take a look but that might take a while since I'm currently busy with some other work.

[mihe]

Unfortunately I'm quite busy as well, and won't have time to look into this any time soon. For the time being I'm fine with simply doing the overriding through the createProject options instead.

[aeisenberg]

We spent a few hours trying to track this down. Once we figured this out, the workaround is not too bad. If it is not easy to add this feature, I have two suggestions of temporary fixes:

1. Add some documentation to say that extends is not supported in the tsconfig files.
2. Add a warning with a meaningful message if an extends property is found.

It looks like support for inheritance was added in version 3.2.0.

[ivogabe]

It looks like support for inheritance was added in version 3.2.0.

Yes, 'extends' is now supported and several bugs of it were fixed in version 3.2.1.