`--showConfig` is ignoring missing `extends` file

[vvakame]

TypeScript Version: 3.2.0-dev.20181117

and local build with 608a830

Search Terms:
showConfig

Code

{
  "extends": "./notExists.tsconfig.json",
  "compilerOptions": {
    "target": "esnext",
    "module": "commonjs",
    "strict": true
  }
}

Expected behavior:
show error TS5058: The specified path does not exist: '/foobar/notExists.tsconfig.json'. error message.

Actual behavior:
don't report any error and dump incompleteness config value.

Playground Link: None

Related Issues: #27353

I made a patch to this issue.
If this is a problem, I can submit this patch.
vvakame@d6d9c9e

[weswigham]

I've gone back and forth on this - the diagnostics are obviously useful for fixing the config; however then you can't rely on the output with the flag on always being JSON. Then again, the return code changes when diagnostics are emitted, so that might be fine...

@vvakame I think we'll take a PR for the change, but the JSON document and the diagnostics should be either/or - meaning if there are diagnostics for the config file, we print those, rather than the config. I think that's probably the way to go.

[vvakame]

@weswigham thanks! I made a PR #28612 😉