Unexpected error from forceConsistentCasingInFileNames when using `extends` in tsconfig

[bitjson]

TypeScript Version: 2.4.0

On case-insensitive systems, projects with forceConsistentCasingInFileNames enabled – which are located at a path which contains capital letters – issue an unexpected compiler error:

error TS1149: File name '[...]/capitalization-in-path/src/index.ts' differs from already included file name '[...]/CAPITALIZATION-IN-PATH/src/index.ts' only in casing.

Similar to #9934, #10095, and #10474, but seems to be a slightly different issue.

Example repo
https://github.com/bitjson/typescript-bug

Specifically, this is only happening when tsc is passed a tsconfig.json that extends another tsconfig.json. In the example repo, note that there is no difference in configuration:

tsc -p tsconfig.json" # working
tsc -p config/tsconfig.json # error

where config/tsconfig.json contains only:

{
  "extends": "../tsconfig"
}

[ExplodingCabbage]

It's worth noting that this affects pretty much any Mac user with a TypeScript project in their home directory, since Macs use a case-insensitive file system by default and the home directory is by default contained in the Users folder (with a capital U). I just had to turn forceConsistentCasingInFileNames off to fix this error:

error TS1149: File name '/users/markamery/my-project/node_modules/@types/body-parser/index.d.ts' differs from already included file name '/Users/markamery/my-project/node_modules/@types/body-parser/index.d.ts' only in casing.

[mhegazy]

looks like a duplicate of #17617

[ip]

@mhegazy Please reopen, the duplicate you mentioned is closed, yet this bug is still there on TS 2.5.3.

[ExplodingCabbage]

@ip at the linked duplicate, @mhegazy claimed the fix would go out in 2.6, so the bug still existing in 2.5.3 is expected. Have you tried reproducing in 2.6? (I haven't, yet.)

[ip]

@ExplodingCabbage Ok then, thanks for the info.

[patrickhousley]

@ExplodingCabbage I am still seeing this issue with 2.6.1:
error TS1149: File name '/users/patrickhousley/documents/projects/my-projects/my-project/node_modules/@types/lodash/index.d.ts' differs from already included file name '/Users/patrickhousley/Documents/projects/my-projects/my-project/node_modules/@types/lodash/index.d.ts' only in casing.

[mhegazy]

@patrickhousley can you please file a new issue, and give us some more context to be able to reproduce it locally.

[ip]

It's still there in 2.7.1.

@mhegazy I believe this isn't a duplicate of the issue you mentioned, especially since that issue is closed. So please reopen.

For now I just avoided using extends property and merging my configs manually, it works.

[xilaraux]

TypeScript version: 2.6.2

I faced the same issue.

My guess is this causing because of extending of tsconfig from the root level resolved typeRoots from its level.
In child tsconfig I added typeRoots relative to it. It helped me.

Parent tsconfig.json:

{
    ...,
    "compilerOptions": {
        ...,
        "typeRoots": [
            "../../node_modules/@types/"
        ]
    },
   ...
}

Child tsconfig:

{
    "extends": "../tsconfig.json",
    "compilerOptions": {
        ...,
        "typeRoots": [
            "../../../node_modules/@types/"
        ]
    },
    ...
}