Catch-all "*": ["./src/*"] path (the official TS7 baseUrl replacement) is never rewritten

[TrevorSayre]

Summary

With baseUrl removed and a single catch-all paths entry (e.g. "*": ["./src/*"]),
tsc-alias leaves all matching imports unchanged. This is the exact configuration
the TypeScript team recommends as the replacement for baseUrl in TypeScript 7
(microsoft/TypeScript#62207), so it is likely to become a common setup.

Related: #255 (closed) and #134 describe the broader no-baseUrl basePath
miscomputation. This report is narrower and, I think, more actionable: it pins
down why the catch-all specifically produces no output, with source references.

Environment

• tsc-alias: 1.9.2 (latest)
• TypeScript: 7.0.2 (confirmed; tsc itself compiles the catch-all config without
  error, so TS7 resolves "*": ["./src/*"] fine and only tsc-alias fails to
  rewrite the emitted import). Also reproduces on TypeScript 6.x.
• Config: module/moduleResolution: NodeNext, rootDir: src, outDir: dist,
  no baseUrl.

Minimal reproduction

tsconfig.json:

{
  "compilerOptions": {
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "target": "ESNext",
    "rootDir": "src",
    "outDir": "dist",
    "paths": {
      "*": ["./src/*"],
    },
  },
  "include": ["src/**/*"],
}

src/config.ts:

export const NAME = "example";

src/index.ts:

import { NAME } from "config.js";
console.log(NAME);

Run:

tsc && tsc-alias -p tsconfig.json

Expected dist/index.js:

import { NAME } from "./config.js";

Actual dist/index.js (unchanged, fails at runtime under Node):

import { NAME } from "config.js";

Root cause

Two things combine in 1.9.2:

1. The catch-all alias is dropped from the trie. In dist/utils/trie.js,
   buildAliasTrie computes prefix = alias.replace(/\*$/, ""), which is ""
   for a bare "*", and then only adds the alias when if (alias.prefix) is
   truthy. An empty prefix is falsy, so "*" is silently skipped and the default
   replacer never has anything to match.

2. The implicit-baseUrl branch never sets baseUrl. In
   dist/helpers/config.js, when baseUrl is absent but paths exist, the
   else if branch rewrites each path relative to rootDir ("./src/*" becomes
   "*") but does not assign config.baseUrl = rootDir. baseUrl therefore
   defaults to "", so the built-in base-url replacer stays disabled
   (enabled: !!config.baseUrl in dist/helpers/replacers.js) and cannot pick up
   the bare specifier either.

Net effect: neither the default (trie) replacer nor the base-url replacer handles
the catch-all, so nothing is rewritten.

Suggested fix direction

Either (or both):

• Treat an empty-prefix "*" as a valid catch-all in buildAliasTrie (match any
  non-relative specifier, resolving the target against outDir), rather than
  discarding it.
• In the implicit-baseUrl branch of loadConfig, set config.baseUrl = rootDir
  (as PR fix: support ts 6 implicit baseURL #259 originally did) so the existing base-url replacer activates and
  resolves bare specifiers against outDir by file existence.

Happy to open a PR with a projects/projectNN test case mirroring the TS7
catch-all config if a maintainer confirms this direction fits the current rework
in #262.

Workaround for anyone stuck today

A tiny custom replacer reproduces the base-url behavior without needing baseUrl.
It rewrites any bare specifier that resolves to an emitted file under outDir, and
leaves node_modules imports alone:

// tsc-alias.replacer.cjs
"use strict";
const { statSync } = require("node:fs");
const { dirname, relative, resolve } = require("node:path");

const specifierRegex = /(?<quoted>["'](?<path>[^"'\r\n]+)["'])/;
const isFile = (t) => {
  try {
    return statSync(t).isFile();
  } catch {
    return false;
  }
};

module.exports.default = function localImportsReplacer({ orig, file, config }) {
  const match = orig.match(specifierRegex);
  const specifier = match && match.groups.path;
  if (!specifier || specifier.startsWith(".")) return orig;

  const target = resolve(config.outPath, specifier);
  if (!isFile(target)) return orig;

  let rel = relative(dirname(file), target).replace(/\\/g, "/");
  if (!rel.startsWith(".")) rel = "./" + rel;

  return orig.replace(match.groups.quoted, match.groups.quoted.replace(specifier, rel));
};

Wire it in: tsc-alias -p tsconfig.json --replacer ./tsc-alias.replacer.cjs. Note
this relies on specifiers carrying explicit extensions (config.js,
utils/index.js), which is the norm under NodeNext.

References

• Deprecate, remove support for baseUrl microsoft/TypeScript#62207 (baseUrl removal, "*" catch-all is the recommended replacement)
• tsc-alias should work without baseUrl (required for tsgo compatibility) #255, Paths resolve to the wrong dir (tsc-alias debug: default replacer - Invalid path ) #134 (related no-baseUrl reports)
• fix: support ts 6 implicit baseURL #259, fix: do not activate baseurl mode #262 (prior/ongoing work in this area)

[justkey007]

​High quality issue, thanks a lot for doing the heavy lifting and digging into the source code!

​You're spot on. With TS deprecating baseUrl, this is definitely going to pop up everywhere.

​Regarding the fix direction: making buildAliasTrie handle an empty prefix "" sounds like the cleaner path here. Mutating config.baseUrl under the hood feels a bit too side-effect prone and might mess with how the base-url replacer handles other edge cases.

​I'd be more than happy to review a PR for this! Feel free to open one with the projectNN test case included whenever you're ready.

​Thanks again for the detailed report and for providing a workaround for other users in the meantime.