Missing 'depends' section in ext_emconf.php leads to error
If an extension has no
'depends' section in
ext_emconf.php, but requires packages via
composer.json, then during
install:generatepackagestates an error is raised:
The package "myext" depends on "my/composer-package" which is not present in the system.
'constraints' => ['depends' => ], into
ext_emconf.php it works fine.
Especially for project specific local extensions you may not have any dependencies specified. When it works with the empty depends array, it should also be possible to leave it out entirely.