[gentoo-dev] [PATCH] python-utils-r1.eclass: Add PYTHON_RELAXED_VERSIONS variable

[Patrick McLean]

This adds PYTHON_RELAXED_VERSIONS that ebuilds can set before inheriting the
python eclasses that will make the implementation dependencies be simple slot
dependencies rather than >= dependencies. The purpose of this is for packages in
@system to use to avoid circular dependencies like in bug #720048

Bug: https://bugs.gentoo.org/720048
Signed-off-by: Patrick McLean <chutzpah@g.o>
---
 eclass/python-utils-r1.eclass | 56 ++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 14 deletions(-)

diff --git a/eclass/python-utils-r1.eclass b/eclass/python-utils-r1.eclass
index e85aefda792..e5781605c8e 100644
--- a/eclass/python-utils-r1.eclass
+++ b/eclass/python-utils-r1.eclass
@@ -57,6 +57,17 @@ readonly _PYTHON_ALL_IMPLS
 # which can involve revisions of this eclass that support a different
 # set of Python implementations.
 
+# @ECLASS-VARIABLE: PYTHON_RELAXED_VERSIONS
+# @INTERNAL
+# @DESCRIPTION:
+# Set to a non-empty value in order to make eclass dependencies on
+# Python versions be simple slot dependencies rather than setting
+# a minimum version.
+#
+# This is intended to be set in ebuilds that are part of @system, or
+# are dependencies of Python implementations themselves to avoid
+# circular dependencies with the Python interpreter.
+
 # @FUNCTION: _python_impl_supported
 # @USAGE: <impl>
 # @INTERNAL
@@ -376,20 +387,37 @@ _python_export() {
 				;;
 			PYTHON_PKG_DEP)
 				local d
-				case ${impl} in
-					python2.7)
-						PYTHON_PKG_DEP='>=dev-lang/python-2.7.17-r1:2.7';;
-					python3.6)
-						PYTHON_PKG_DEP=">=dev-lang/python-3.6.10:3.6";;
-					python3.7)
-						PYTHON_PKG_DEP=">=dev-lang/python-3.7.7-r1:3.7";;
-					python3.8)
-						PYTHON_PKG_DEP=">=dev-lang/python-3.8.2:3.8";;
-					pypy3)
-						PYTHON_PKG_DEP='>=dev-python/pypy3-7.3.0:0=';;
-					*)
-						die "Invalid implementation: ${impl}"
-				esac
+				if [[ -z ${PYTHON_RELAXED_VERSIONS} ]]; then
+					case ${impl} in
+						python2.7)
+							PYTHON_PKG_DEP='>=dev-lang/python-2.7.17-r1:2.7';;
+						python3.6)
+							PYTHON_PKG_DEP=">=dev-lang/python-3.6.10:3.6";;
+						python3.7)
+							PYTHON_PKG_DEP=">=dev-lang/python-3.7.7-r1:3.7";;
+						python3.8)
+							PYTHON_PKG_DEP=">=dev-lang/python-3.8.2:3.8";;
+						pypy3)
+							PYTHON_PKG_DEP='>=dev-python/pypy3-7.3.0:0=';;
+						*)
+							die "Invalid implementation: ${impl}"
+					esac
+				else
+					case ${impl} in
+						python2.7)
+							PYTHON_PKG_DEP='dev-lang/python:2.7';;
+						python3.6)
+							PYTHON_PKG_DEP="dev-lang/python:3.6";;
+						python3.7)
+							PYTHON_PKG_DEP="dev-lang/python:3.7";;
+						python3.8)
+							PYTHON_PKG_DEP="dev-lang/python:3.8";;
+						pypy3)
+							PYTHON_PKG_DEP='dev-python/pypy3:0=';;
+						*)
+							die "Invalid implementation: ${impl}"
+					esac
+				fi
 
 				# use-dep
 				if [[ ${PYTHON_REQ_USE} ]]; then
-- 
2.26.2