Symfony version(s) affected

6.3, 6.4-dev, 6.4.0-beta3

Description

Using the default remotely-hosted shims works as expected. If requiring the polyfills as a local vendor asset, an error occurs:

Javascript console

es-module-shims.index-50eab39155ca286f16894eb2ba1c2740.js:7 Uncaught SyntaxError: Invalid or unexpected token (at es-module-shims.index-50eab39155ca286f16894eb2ba1c2740.js:7:12535)

The generated file (assets/vendor/es-module-shims/es-module-shims.index.js) appears to be mangled.

For projects not needing the shim support, explicitly disabling it removes the error. Including it as a CDN asset, however, means the user will need to write a server CSP allowing the remote host, which may be undesirable. In Apache2:

security.conf

Header always set Content-Security-Policy "script-src blob: https://ga.jspm.io;"

How to reproduce

In a Symfony ^6.3 project using AssetMapper, require ES Module Shims as a local dependency:

./bin/console importmap:require es-module-shims

[OK] Package "es-module-shims" added to importmap.php.                               

      Use the new package normally by importing "es-module-shims".

Load the project page in a browser and review the inspector console for errors:

Possible Solution

A workaround if IE11 support isn't needed is to just disable the polyfill:

config/packages/asset_mapper.yaml

framework:
    asset_mapper:
        # The paths to make available to the asset mapper.
        paths:
            - assets/
        importmap_polyfill: false

Additional Context

No response