Path aliases for certain import statements are not resolved when packaging with `@sveltejs/package` 2.5.1+

[maxherrmann]

Describe the bug

When packaging with @sveltejs/package (versions 2.5.1 or higher), path aliases are not resolved for certain import statements, which breaks the package on the consumer side.

The issue was introduced with #14413.

Reproduction

Setup

Assume we have the following alias configuration in svelte.config.js:

alias: {
  $foo: "./src/lib/foo",
}

Assume we have a .ts or .svelte file in the root of ./src/lib with either one of the following import statements (all valid, as per MDN Docs):

import foo, { bar } from '$foo'
import foo, { bar, baz } from '$foo'
import foo, { type bar, type baz } from '$foo'
import foo, * as bar from '$foo'
import _foo from '$foo'
import * as _foo from '$foo'
import '$foo'

Current result after packaging

None of the path aliases have been resolved.

import foo, { bar } from '$foo'
import foo, { bar, baz } from '$foo'
import foo, { type bar, type baz } from '$foo'
import foo, * as bar from '$foo'
import _foo from '$foo'
import * as _foo from '$foo'
import '$foo'

Expected result after packaging

All path aliases have been resolved.

import foo, { bar } from './foo'
import foo, { bar, baz } from './foo'
import foo, { type bar, type baz } from './foo'
import foo, * as bar from './foo'
import _foo from './foo'
import * as _foo from './foo'
import './foo'

Root cause

The current regular expression that identifies path aliases does not seem to capture the following:

• Combinations of default and named¹/namespaced imports
• Default/namespaced imports with identifiers that start with _
• Side-effect-only imports

¹) See #14455 (comment)

Workaround

As a workaround, you can use @sveltejs/package@2.5.0 or rewrite any affected import statements (if possible) so that they are captured by the current regular expression.

Logs

System Info

System:
    OS: macOS 15.6.1
    CPU: (12) arm64 Apple M4 Pro
    Memory: 192.52 MB / 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.16.0 - ~/.nvm/versions/node/v22.16.0/bin/node
    npm: 11.4.1 - ~/.nvm/versions/node/v22.16.0/bin/npm
  Browsers:
    Chrome: 140.0.7339.133
    Edge: 140.0.3485.66
    Safari: 18.6

Severity

serious, but I can work around it

Additional Information

No response

[maxherrmann]

This has been partially fixed in #14462 and combinations of default and named imports are now properly detected and resolved in @sveltejs/package@2.5.3. 👍