pkg/front_end/test/language_versioning/data/package_default_version_is_empty/.dart_tool/package_config.json

/*error: errors=PackagesFileFormat*/
{
    "configVersion": 2,
    "packages": [
        {
            "name": "foo",
            "rootUri": "../lib/",
            "languageVersion": ""
        }
    ]
}