check for .d.ts files for path aliases

[davidparkagoda]

Summary:

Tries to fix a bug where there are false positives, if importing from a d.ts file.
This only occurs if tsconfig uses aliases (paths).

This PR would need another PR to be merged in
dividab/tsconfig-paths#124

Right now tsconfig-paths is returning file paths with the extension stripped, src/something/hi.ts => src/something/hi.
However this extension stripping only removes 1 level of . so when we matched .d.ts files it will incorrectly strip the extension to be like src/something/hi.d.ts => src/something/hi.d.

[mrseanryan]

hi @davidparkagoda

question -
as an alternative to waiting for the ts-config-paths PR,
could we 'patch' our code to get around this:

will incorrectly strip the extension to be like src/something/hi.d.ts => src/something/hi.d.

We could add a TODO to remove our 'patch' once ts-config-paths is updated.

[davidparkagoda]

Yes we could definitely do that but it does not feel great.

Even if we do this 'patch', the workarounds that I see are not great.

We could do something like
matchedPath.replace(/\.d$/, '') but that seems a bit too broad.
or
after we get the matchedPath we check if the file exists matchPath + '.ts' but that is an extra file check.

If you are okay with one of those solutions or have a better workaround I am willing to make the change

[mrseanryan]

| We could do something like
| matchedPath.replace(/.d$/, '') but that seems a bit too broad.

I think this would work?

Or - in which cases would this cause a problem ?

[davidparkagoda]

I know this is kind of edge case but a files named like

file.d.tsx
file.d.js
file.d.jsx

you would need import from javascript like
import { ExportedThing } from 'file.d'; (for file.d.js, ...)

but ts-unsused-exports would be looking for file rather than file.d if I make the matchedPath.replace(/.d$/' '') change

[mrseanryan]

Hmm wouldn't that also happen with the fix for tsconfig-paths?

[davidparkagoda]

No.

When tsconfig-paths is iterating the list of extensions that we pass to it, I modified it so that it will note the extension length of the matched path when found. This is make it so that we only strip out the length of the of the matched extension.

You will not be able to have the same kind of "bug" with the fix for tsconfig-paths without having a really weird webpack or configuration

const EXTENSIONS = ['.d.ts', '.ts', '.tsx', '.d.js', '.js', '.jsx'];
Now if you imported file, which through weird configuration, points to file.d.js, tsconfig-paths will return file which is correct given the extensions that we passed to tsconfig-paths

However if you imported file.d, tsconfig-paths will try
'file.d' + '.d.js', which does not exist
'file.d' + .js'which does exist.tsconfig-pathsalso knows the matched extension so it only strips.js`

[mrseanryan]

I see. So in such cases, tsconfig-paths checks for file exists.

Question is that covered by this approach:

after we get the matchedPath we check if the file exists matchPath + '.ts' but that is an extra file check.

[davidparkagoda]

yes this would work. something like

if (matchedPath.endsWith('.d')) {
    if (matchedPath + '.ts') file exists {
        matchedPath = matchedPath.slice(0, -2);
    }
}

[mrseanryan]

@davidparkagoda

is this PR completed ?

(it looks good to me).

Thanks,
Sean

[davidparkagoda]

@mrseanryan yup everything should be good. Please go ahead and do anything to get this merged in :D

[mrseanryan]

@davidparkagoda
Merged it to master (used a separate PR due to some github/travis glitch).
Hopefully it will be released soon.

Thank you for your contribution !