mmgen-wallet/test/overlay/__init__.py

import sys,os,shutil

def get_overlay_tree_dir(repo_root):
	return os.path.join(repo_root,'test','overlay','tree')

def overlay_setup(repo_root):

	def process_srcdir(pkgname,d):
		relpath = d.split('.')
		srcdir = os.path.join(repo_root,*relpath)
		destdir = os.path.join(overlay_tree_dir,*relpath)
		fakemod_dir = os.path.join(fakemod_root,pkgname,*(relpath[1:]))
		os.makedirs(destdir)
		for fn in os.listdir(srcdir):
			if (
				fn.endswith('.py') or
				d == f'{pkgname}.data' or
				(d == f'mmgen.proto.secp256k1' and fn.startswith('secp256k1'))
			):
				if os.path.exists(os.path.join(fakemod_dir,fn)):
					make_link(
						os.path.join(fakemod_dir,fn),
						os.path.join(destdir,fn) )
#					link_fn = fn.removesuffix('.py') + '_orig.py' # Python 3.9
					link_fn = fn[:-3] + '_orig.py'
				else:
					link_fn = fn
				make_link(
					os.path.join(srcdir,fn),
					os.path.join(destdir,link_fn) )

	overlay_tree_dir = get_overlay_tree_dir(repo_root)
	fakemod_root = os.path.join(repo_root,'test','overlay','fakemods')
	common_path = os.path.join(os.path.sep,'test','overlay','fakemods')
	pkgdata = ((
			os.path.realpath(e.path)[:-len(os.path.join(common_path,e.name))], # Python 3.9: removesuffix()
			e.name
		) for e in os.scandir(fakemod_root) if e.is_dir() )

	for repodir,pkgname in pkgdata:
		if not os.path.exists(os.path.join(overlay_tree_dir,pkgname)):

			sys.stderr.write(f'Setting up overlay tree: {pkgname}\n')

			make_link = os.symlink if sys.platform == 'linux' else shutil.copy2
			shutil.rmtree(os.path.join(overlay_tree_dir,pkgname),ignore_errors=True)

			import configparser
			cfg = configparser.ConfigParser()
			cfg.read(os.path.join(repodir,'setup.cfg'))

			for d in cfg.get('options','packages').split():
				process_srcdir(pkgname,d)

	return overlay_tree_dir