def _analyse_explicit_layout(self) -> bool:
        """The user can explicitly give a package layout via ``package_dir``"""
        package_dir = self._package_dir.copy()  # don't modify directly
        package_dir.pop("", None)  # This falls under the "src-layout" umbrella
        root_dir = self._root_dir

        if not package_dir:
            return False

        log.debug(f"`explicit-layout` detected -- analysing {package_dir}")
        pkgs = chain_iter(
            _find_packages_within(pkg, os.path.join(root_dir, parent_dir))
            for pkg, parent_dir in package_dir.items()
        )
        self.dist.packages = list(pkgs)
        log.debug(f"discovered packages -- {self.dist.packages}")
        return True
The user can explicitly give a package layout via ``package_dir``
product/gradle-plugin/src/main/python/setuptools/discovery.py