Dynamic install_requires in setup.py

Question

I'm writing a python package with installable sub-packages as is shown below.

my_project
├── subpackage1
│   ├── foo.py
│   └── setup.py
├── subpackage2
│   ├── bar.py
│   └── setup.py
└── setup.py [main]

My setup.py is like the following:

from setuptools import setup, find_packages
from setuptools.command.install import install

# new install class
class InstallCommand(install):
    # pass argument subpackage from pip install to setup.py
    user_options = install.user_options + [
        ('subpackage=', None, None),  
    ]

    def initialize_options(self):
        install.initialize_options(self)
        self.subpackage = None

    def finalize_options(self):
        install.finalize_options(self)

    def run(self):

        if self.subpackage is None:
            # install all sub-packages
            subpackages = ['my_project.'+x for x in find_packages('./my_project', exclude=['*.tests', '*.tests.*', 'tests.*', 'tests'])]
            self.distribution.packages += ['my_project'] + subpackages 

        else:  
            subpackages = self.subpackage.split(', ')
            print("Install sub-packages:", self.subpackage)
            # install only specific sub-packages
            subpackages = ['my_project.'+x for x in subpackages]
            self.distribution.packages += ['my_project'] + subpackages

        install.run(self)

metadata = dict(
    name='my_project',
    packages=[],
    install_requires=[],
    setup_requires=[],
    cmdclass={
        'install': InstallCommand
    }
    )

setup(**metadata)

It allows me to install any sub-packges with a command like

$ pip install /path/to/main setup.py/ --install-option="--subpackage=subpackage1, subpackage2"

However, this setup.py doesn't install the dependencies for sub-packages I selected (sub-package dependencies are contained in install_requires of each sub-package setup.py).

Is there any way to have a dynamic install_requires argument for setup() based on the command line input "subpackage"?

I have tried to modify the function run(self) in the class InstallCommand(install) by adding

self.distribution.install_requires += dependency_ls_function of subpackage

but it messed up the command line input and makes the installation failed.

I also tried a very simple example with a package 'pipreqs', which is not installed in the environment.

self.distribution.install_requires += ['pipreqs']

The installation went well, but with a warning

my_project requires pipreqs, which is not installed.

I guess before the command 'install', the install_requires is already handled.