[gentoo-python] [PATCH] Add python_gen_cond_dep().

[Michał Górny]

I don't have a good idea how to make enforcing USE deps inside easier
than $(python_gen_cond_dep dev-foo/bar[$(python_gen_usedep IMPLS)]
IMPLS) without adding some risky magic.
---
 gx86/eclass/python-r1.eclass | 47 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/gx86/eclass/python-r1.eclass b/gx86/eclass/python-r1.eclass
index 40ce68b..32ac3ca 100644
--- a/gx86/eclass/python-r1.eclass
+++ b/gx86/eclass/python-r1.eclass
@@ -178,7 +178,7 @@ _python_set_globals() {
 _python_set_globals
 
 # @FUNCTION: python_gen_usedep
-# @USAGE: pattern [...]
+# @USAGE: <pattern> [...]
 # @DESCRIPTION:
 # Output a USE dependency string for Python implementations which
 # are both in PYTHON_COMPAT and match any of the patterns passed
@@ -221,7 +221,7 @@ python_gen_usedep() {
 }
 
 # @FUNCTION: python_gen_useflags
-# @USAGE: pattern [...]
+# @USAGE: <pattern> [...]
 # @DESCRIPTION:
 # Output a list of USE flags for Python implementations which
 # are both in PYTHON_COMPAT and match any of the patterns passed
@@ -255,6 +255,49 @@ python_gen_useflags() {
 	echo ${matches[@]}
 }
 
+# @FUNCTION: python_gen_cond_dep
+# @USAGE: <dependency> <pattern> [...]
+# @DESCRIPTION:
+# Output a list of <dependency>-ies made conditional to USE flags
+# of Python implementations which are both in PYTHON_COMPAT and match
+# any of the patterns passed as the remaining parameters.
+#
+# Please note that USE constraints on the package need to be enforced
+# separately. Therefore, the dependency usually needs to use
+# python_gen_usedep as well.
+#
+# Example:
+# @CODE
+# PYTHON_COMPAT=( python{2_5,2_6,2_7} )
+# RDEPEND="$(python_gen_cond_dep dev-python/unittest2 python{2_5,2_6})"
+# @CODE
+#
+# It will cause the variable to look like:
+# @CODE
+# RDEPEND="python_targets_python2_5? ( dev-python/unittest2 )
+#	python_targets_python2_6? ( dev-python/unittest2 )"
+# @CODE
+python_gen_cond_dep() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local impl pattern
+	local matches=()
+
+	local dep=${1}
+	shift
+
+	for impl in "${PYTHON_COMPAT[@]}"; do
+		for pattern; do
+			if [[ ${impl} == ${pattern} ]]; then
+				matches+=( "python_targets_${impl}? ( ${dep} )" )
+				break
+			fi
+		done
+	done
+
+	echo ${matches[@]}
+}
+
 # @ECLASS-VARIABLE: BUILD_DIR
 # @DESCRIPTION:
 # The current build directory. In global scope, it is supposed to
-- 
1.8.0.2