fix(esm): use tsc-alias to append .js extensions to ESM imports

[harshitanand]

What

Fixes ESM module resolution errors in @bitgo/abstract-utxo and @bitgo/utxo-core by adding .js extensions to relative imports in compiled output.

How

Uses tsc-alias with fileExtensionReplacer — the standard, well-tested approach for this problem — instead of a custom post-processor script.

• build:esm in both modules now runs tsc-alias -p tsconfig.esm.json after tsc
• tsc-alias ^1.8.10 added to devDependencies in both modules
• fileExtensionReplacer configured under the "tsc-alias" key in each module's package.json
• scripts/fix-esm.js retired (file contains a comment pointing to the new approach)

tsc-alias handles barrel re-exports, declaration files, dynamic imports, and directory index resolution — all edge cases the custom script would have missed.

Testing

• yarn build:esm — CLEAN (both modules)
• yarn test — 1942 passed, 0 failed

Related

Closes #7660

[kaustubhbitgo]

From the original issue I would suggest to either use tsc-alias or bundler option as they cover multiple edge cases when it comes to resolve imports / other issues in esm.

[harshitanand]

Thanks for the review! Understood — the custom post-processor is brittle compared to tsc-alias which handles the full range of ESM path-rewriting edge cases (barrel re-exports, conditional imports, declaration files, etc.).

Could you clarify which approach you'd prefer me to implement?

1. tsc-alias — add as a dev dependency, run tsc-alias after tsc in the build:esm step (e.g. "build:esm": "tsc -p tsconfig.esm.json && tsc-alias -p tsconfig.esm.json")
2. Bundler option — switch the ESM output to use a bundler (esbuild/rollup) that handles module resolution natively

Happy to implement either. tsc-alias is a minimal change with no bundler adoption overhead — I'll go that route unless you have a preference for the bundler approach.

[alextse-bg]

flushing, please reping when the fix is ready

[harshitanand]

@alextse-bg Fix is ready — switched from the custom fix-esm.js post-processor to tsc-alias as suggested (commit 34829a0).

What changed:

• build:esm in both abstract-utxo and utxo-core now runs tsc-alias -p tsconfig.esm.json after tsc
• tsc-alias added to devDependencies in both modules (^1.8.10)
• fileExtensionReplacer configured in each module's package.json under the "tsc-alias" key — this appends .js to relative imports in the compiled ESM output, which is the canonical way to handle this
• scripts/fix-esm.js retired (file now contains only a comment pointing to the new approach)

tsc-alias covers barrel re-exports, declaration files, dynamic imports, and all the edge cases the custom script missed. Ready for re-review.

[harshitanand]

@alextse-bg Rebased onto latest master (53f2bea) — picked up the version bumps in abstract-utxo (10.23.1→10.24.0) and utxo-core (1.36.0→1.36.1) and updated dependency versions. The tsc-alias changes are intact. Also updated the PR description to reflect the current implementation. Ready for re-review.

[harshitanand]

@alextse-bg Rebased onto current master (e385447) — conflict resolved, tsc-alias changes intact (54a39e9). Ready for re-review.