[@rollup/plugin-typescript]: Source-map source paths break if "sourceRoot" is specified #1948

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1. shellscape commented on Mar 8, 2026

   

   shellscape

   on Mar 8, 2026

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   @CharlieHelps using the reproduction link and the issue description, please do a best-effort triage of this issue and recommend a reasonable fix. If you have questions, please ask them first and provide 1-4 suggested answers in a b c d format. this has come up in issues in this repo in the past and there are commits around this subject, be sure to research and consider those.
2. charliecreates commented on Mar 8, 2026

   

   charliecreatesBot

   on Mar 8, 2026 – with CharlieCreates

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   Thanks for the ping — I did a best-effort triage and looked at prior related work.

   I can reproduce this on master with a local fixture mirroring the report (sourceRoot: "./src"): final map.sources entries get duplicated path segments (examples: .../src/foo/src/foo/foo.ts, .../src/src/index.ts). Removing sourceRoot produces correct paths.

   Likely root cause:

   • packages/typescript/src/outputFile.ts (findTypescriptOutput) currently passes the emitted TS .map through unchanged.
   • packages/typescript/src/index.ts returns that map directly from load().
   • With relative sourceRoot, map paths are not rebased for Rollup’s collapse base (dirname(id)), so path segments effectively get re-applied and produce invalid/duplicated sources paths.

   Related history I considered:

   • [@rollup/plugin-typescript] unable to generate source map sources correctly #1861 (same symptom family: duplicated src/src-style sourcemap paths)
   • fix(typescript): fix sourcemap sourcecontent referencing non-existent files #1571 (prior sourcemap-path fix in this same outputFile/index flow)
   • fix(typescript): rebase sourcemap sources paths when outDir differs from source directory #1967 (open PR for Incorrect sourcemap sources paths when outDir differs from source directory #1966 outDir rebasing): useful context, but does not address this sourceRoot duplication case.

   Recommended fix:

   1. In packages/typescript/src/outputFile.ts, parse and rewrite emitted sourcemaps before returning them:
      • fold sourceRoot into each sources entry,
      • resolve/rebase to paths relative to dirname(id),
      • normalize to POSIX (/) with existing normalization utilities,
      • remove sourceRoot after folding to avoid downstream double-application,
      • skip rebasing for URL-like sourceRoot / sources entries.
   2. Add a regression fixture + test for this exact case (sourceRoot: "./src" with nested imports) asserting no duplicated segments in final map.sources.
   3. Keep companion regression coverage for the Incorrect sourcemap sources paths when outDir differs from source directory #1966/fix(typescript): rebase sourcemap sources paths when outDir differs from source directory #1967 outDir scenario to avoid regressions across both path-rebasing paths.

   If helpful, I can follow up with a PR implementing this approach.