[PATCH v4] python*-setuptools: add separate packages for pkg_resources module

[luca.boccassi@gmail.com]

From: Luca Boccassi <luca.boccassi@microsoft.com>

The pkg_resources Python module is useful by itself, for example for
automatic loading of resources shipped in a Python package.
Add separate packages for it, so that users can depend on them
individually and avoid pulling in the entire setuptools, which
include scripts to download other packages, which might not be
desired on minimal images.

Other distributions like Debian and Ubuntu already split setuptools
and pkg-resources in this way.

The setuptools packages now depend on the new pkg-resources packages,
to avoid regressions for other packages that depend on them
already.

Signed-off-by: Luca Boccassi <luca.boccassi@microsoft.com>
---
v2: restrict new RDEPENDS to class-target. As advised by Alexander, bitbake
    cannot resolve native rdeps that mention package names rather than
    recipe names.
v3: manually add RPROVIDES to the native class instead of restricting the
    RDEPENDS to the target class as a better workaround. Also document why
    the package is being split.
v4: re-send to the correct thread, no changes.

 meta/recipes-devtools/python/python-setuptools.inc | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/meta/recipes-devtools/python/python-setuptools.inc b/meta/recipes-devtools/python/python-setuptools.inc
index 357aa07086..f49e078697 100644
--- a/meta/recipes-devtools/python/python-setuptools.inc
+++ b/meta/recipes-devtools/python/python-setuptools.inc
@@ -37,3 +37,14 @@ do_install_prepend() {
 }
 
 BBCLASSEXTEND = "native nativesdk"
+
+# The pkg-resources module can be used by itself, without the package downloader
+# and easy_install. Ship it in a separate package so that it can be used by
+# minimal distributions.
+PACKAGES =+ "${PYTHON_PN}-pkg-resources "
+FILES_${PYTHON_PN}-pkg-resources = "${PYTHON_SITEPACKAGES_DIR}/pkg_resources/*"
+# Due to the way OE-Core implemented native recipes, the native class cannot
+# have a dependency on something that is not a recipe name. Work around that by
+# manually setting RPROVIDES.
+RDEPENDS_${PN}_append = " ${PYTHON_PN}-pkg-resources"
+RPROVIDES_append_class-native = " ${PYTHON_PN}-pkg-resources-native"
-- 
2.20.1