Current Behavior

When using the declarationMap option in tsconfig.json, the sources array in declaration map files does not contain correct relative paths. Repro steps:

1. git clone https://github.com/justingrant/ts-declaration-map-repro.git
2. cd ts-declaration-map-repro
3. yarn
4. yarn run with-tsc - this will simply run tsc against this repo.
5. Open ./dist/index.d.ts.map. It will begin with:
   {"version":3,"file":"index.d.ts","sourceRoot":"","sources":["../src/index.tsx"]. Note the correct relative path to index.tsx
6. yarn run with-tsdx which uses tdsx instead of tsc but uses the same TS config.
7. Open ./dist/index.d.ts.map again. Here's what you'll see:
   {"version":3,"file":"index.d.ts","sourceRoot":"","sources":["src/index.tsx"]. Note that the path to index.tsx is incorrectly relative to the project root, not relative to dist.

Expected behavior

Correct relative path to index.tsx (../src/index.tsx) in the map file's sources array.

Suggested solution(s)

I'm assuming that there's a way to configure rollup-plugin-typescript2 so that declaration maps are emitted with the correct paths.

Additional context

Note that only declaration map files are affected. Relative paths in regular sourcemap files works fine.

I'm not sure if this is a problem with tsdx or rollup-plugin-typescript2. But I didn't see any mention of this problem in rollup-plugin-typescript2's issue list, so I figured that tsdx may be the culprit because it's the new kid on the block. I'm assuming (perhaps naively) that if the problem was in rollup-plugin-typescript2 that it would have been reported in its GitHub issues already.

At first I thought that this problem was related to #465, but I think that issue is solely about how to handle the declarationDir config setting which I'm not using at all. Instead, I'm relying on the same outDir folder for both transpiled output and for declaration output.

This issue may be a dupe of #135, but I'm not sure, because #135 has a much more complex config. But the problem does look similar: in both issues the relative path to the source files is missing in declaration maps emitted by tsdx.

BTW, great library! Glad you're building this.

Your environment