Allow tsconfig.json when input files are specified

[brapifra]

I don't know why the tsconfig.json is ignored even when the --project or -p option is specified.
In my opinion, the right implementation should be:

• If no --project or -p option: Ignore tsconfig.json
• Otherwise: Use the configuration file specified. All the options used in the command line should overwrite the ones of the configuration file. E.g. The include/exclude keys of the tsconfig.json will be ignored when input files are specified.

I don't know why the tsconfig.json is ignored even when the --project or -p option is specified.

Could you provide a repro for a situation where tsconfig is ignored?

[brapifra]

Sure @Andy-MS , but I mean, this is not even a bug. This behaviour is explicitly explained in the docs: When input files are specified on the command line, tsconfig.json files are ignored.

When you do tsc file.ts -p tsconfig.json you get:

The lines of code are pretty easy to find

I just can't understand why it's implemented this way.

Probably because no one's implemented it -- could you explain what the use cases are?

[brapifra]

A pretty common practice is to have a pre-commit hook to compile only the staged files in your git project (It makes no sense to compile all the project).
If you try to create this hook that runs tsc over each staged file, you won't be able to use the tsconfig.json, as you are specifying some input files. @Andy-MS

[jescalan]

I have another use case for this. We have many projects that use typescript, and would like to reduce boilerplate and keep our typescript config in one place, so it can be uniformly applied across all our projects for consistency.

At the moment, there isn't a way to do this, since you can't specify both a glob of files to check, and an external path to a tsconfig.json file. The only workaround in the meantime is to copy/paste a tsconfig.json file into the root of every project and have it only contain an "extends" statement. This isn't the end of the world, but it's more boilerplate than we want - the fewer duplicate files across multiple projects we can have, the better.

This same goal is easily accomplished with TSLint, by using their --config option as well as a glob of files to lint. Is there any specific reason why it is disallowed by typescript itself? If not, I would be happy to take a stab at implementing it via pull request, just want to make sure its ok with maintainers.

[zpdDG4gta8XKpMCd]

related, but never considered #12958