[gentoo-python] [PATCH 1/2] Require EAPI=5 for python-single-r1.

[gentoo-python] [PATCH 1/2] Require EAPI=5 for python-single-r1.

[Michał Górny]

The EAPIs before '5' have USE_EXPAND flags in implicit IUSE, therefore
making it impossible to use '(+)' and '(-)' deps on them. This problem
can be noticed in Paludis (bug #447524) [1].

[1]:https://bugs.gentoo.org/show_bug.cgi?id=447524
---
 gx86/eclass/python-single-r1.eclass | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gx86/eclass/python-single-r1.eclass b/gx86/eclass/python-single-r1.eclass
index 51807f2..d9800e1 100644
--- a/gx86/eclass/python-single-r1.eclass
+++ b/gx86/eclass/python-single-r1.eclass
@@ -32,11 +32,13 @@
 # http://www.gentoo.org/proj/en/Python/python-r1/dev-guide.xml
 
 case "${EAPI:-0}" in
-	0|1|2|3)
+	0|1|2|3|4)
 		die "Unsupported EAPI=${EAPI:-0} (too old) for ${ECLASS}"
 		;;
-	4|5)
-		# EAPI=4 needed by python-r1
+	5)
+		# EAPIs before '5' have implicit USE flags for USE_EXPAND
+		# making the '(+)' use-deps useless in paludis.
+		# Bug #447524.
 		;;
 	*)
 		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
-- 
1.8.0.2

[gentoo-python] [PATCH 2/2] Re-enable python-r1 -> python-single-r1 dep prevention in EAPI 5+.

[Michał Górny]

---
 gx86/eclass/python-r1.eclass | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/gx86/eclass/python-r1.eclass b/gx86/eclass/python-r1.eclass
index cfd0a36..3cae4f0 100644
--- a/gx86/eclass/python-r1.eclass
+++ b/gx86/eclass/python-r1.eclass
@@ -133,12 +133,35 @@ fi
 
 _python_set_globals() {
 	local flags=( "${PYTHON_COMPAT[@]/#/python_targets_}" )
-	#local flags_st=( "${PYTHON_COMPAT[@]/#/-python_single_target_}" )
 	local optflags=${flags[@]/%/?}
-	#optflags+=,${flags_st[@]/%/(-)}
 
-	# PYTHON_SINGLE_TARGET safety check temporarily disabled
-	# because of issues with paludis, bug #447524.
+	# Here's a nice trick to prevent python-r1 packages from depending
+	# on python-single-r1 packages.
+	#
+	# python-single-r1 enforces at least one PYTHON_SINGLE_TARGET
+	# through REQUIRED_USE. Therefore, we can assume that
+	# python-single-r1 packages have at least one flag set.
+	#
+	# If packages does not use python-single-r1, it should have no
+	# PYTHON_SINGLE_TARGET flags.
+	#
+	# The '-python_single_target...(-)' construct is always true when
+	# there's no PYTHON_SINGLE_TARGET flags. If there is at least one
+	# such flag, there will be at least one set, and the relevant
+	# constraint will prevent the package from being merged.
+	#
+	# Therefore, developer trying to depend on python-single-r1 package
+	# will be unable to merge the package. This should be enough to
+	# prevent him from committing one.
+	#
+	# In EAPI < 5, an implicit IUSE is added for all USE_EXPAND
+	# variables, making '(-)' deps unusable on them. This can be seen
+	# in Paludis (bug #447524). We need at least EAPI=5 for this to work
+	# correctly.
+	if ! has "${EAPI}" 4; then
+		local flags_st=( "${PYTHON_COMPAT[@]/#/-python_single_target_}" )
+		optflags+=,${flags_st[@]/%/(-)}
+	fi
 
 	IUSE=${flags[*]}
 	REQUIRED_USE="|| ( ${flags[*]} )"
-- 
1.8.0.2

Re: [gentoo-python] [PATCH 1/2] Require EAPI=5 for python-single-r1.

[Michał Górny]

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On Mon, 17 Dec 2012 01:28:22 +0100
Michał Górny <mgorny@gentoo.org> wrote:

> The EAPIs before '5' have USE_EXPAND flags in implicit IUSE, therefore
> making it impossible to use '(+)' and '(-)' deps on them. This problem
> can be noticed in Paludis (bug #447524) [1].
> 
> [1]:https://bugs.gentoo.org/show_bug.cgi?id=447524

Please forget about the patches. My late-night logic had a major flow.

The nature of the issue is that all dependent packages have to be
EAPI=5. Therefore, we effectively need to make whole python-r1 require
EAPI=5.

If nobody objects, I'll:

a) add a verbose warning when python-r1 is used with EAPI=4,

b) bump all packages to EAPI=5 (the stable ones preferably with a ping
to the arch team),

c) after a few days, replacing the warning with a fatal error.

-- 
Best regards,
Michał Górny

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