TypeScript language service breaks down when wrong casing is used for imports

[dbaeumer]

Copied from: https://code.visualstudio.com/Issues/Detail/20178

I was experiencing a bizarre issue where the TS language service broke down and wouldn't underline errors in my code. After pulling my hair out for half an hour, I figured out it was because I was doing a file import with the wrong case e.g.

import Engine from "./Engine"

instead of

import Engine from "./engine"

The default class exported was named 'Engine' which I think might have also had something to do with it.

Open the attached folder in VS Code, then pick the "engine.ts" file and notice that there is an undefined symbol ("jjj_this_is_an_error") that is not red underlined.

I would expect a better error on the erroneous import instead of the imported file no longer having proper language services. :)

[mhegazy]

looks like #5149.

I do agree a better experience is needed here.

[mhegazy]

@vladima, what can we do here?

[mhegazy]

thanks to @vladima, this is not a duplicate, this is a bug in tsserver. fix queued.

[mhegazy]

The issue is that tsserver was using a case sensitive map to store files, so looking up a file with a different case did not work. this should be fixed in TS 1.7, by #5436.

Now ideally, you would want a warring if you reference a module with the wring case, for this use the new flag --forceConsistentCasingInFileNames added in #5275, to check that you always reference the same file using consistent naming this will be available in TS 1.8.

[xirzec]

@mhegazy Thanks for the quick fix! 👍