ext_emconf.php 

Deprecated since version 14.2

Using the ext_emconf.php file in extensions is deprecated. TYPO3 extensions that still ship an ext_emconf.php file but do not declare future compatibility to omit this file will trigger a deprecation message during cache warm-up. version and dependency metadata should now be defined in the extension's composer.json file. The file may still need to be kept for compatibility with third-party tools such as TYPO3 TER and Tailor. For older ext_emconf.php documentation see.

Migration from ext_emconf.php to composer.json 

Use of ext_emconf.php in extensions has been deprecated (Deprecation #108345). If your extension needs to be compatible with TYPO3 Classic mode, add the following to the composer.json file in your extension:

  • Set the extension version in the version field. This version should match the version previously defined in ext_emconf.php and the released Git tag.
  • Declare any plain (non-TYPO3 extension) Composer package dependencies (rather than on other TYPO3 extensions which are specified under require) in extra.typo3/cms.Package.providesPackages.
  • If your extension does not have any Composer package dependencies, set providesPackages to an empty object. This avoids deprecation messages and declares future compatibility with TYPO3 Classic mode.

See Classic-mode compatible composer.json