python-single-r1.eclass: Revert "Remove unused PYTHON_TARGETS"

Pushed too many commits.

Signed-off-by: Michał Górny <[email protected]>

eclass/python-single-r1.eclass

@@ -89,9 +89,9 @@ EXPORT_FUNCTIONS pkg_setup
 #
 # It should be noted that in order to preserve metadata immutability,
 # PYTHON_COMPAT_OVERRIDE does not affect IUSE nor dependencies.
-# The state of PYTHON_SINGLE_TARGET is ignored, and the implementation
-# in PYTHON_COMPAT_OVERRIDE is built instead.  Dependencies need to be
-# satisfied manually.
+# The state of PYTHON_TARGETS and PYTHON_SINGLE_TARGET is ignored,
+# and the implementation in PYTHON_COMPAT_OVERRIDE is built instead.
+# Dependencies need to be satisfied manually.
 #
 # Example:
 # @CODE
@@ -178,8 +178,10 @@ EXPORT_FUNCTIONS pkg_setup
 
 # @ECLASS-VARIABLE: PYTHON_REQUIRED_USE
 # @DESCRIPTION:
-# This is an eclass-generated required-use expression which ensures
-# that exactly one PYTHON_SINGLE_TARGET value has been enabled.
+# This is an eclass-generated required-use expression which ensures the following
+# when more than one python implementation is possible:
+# 1. Exactly one PYTHON_SINGLE_TARGET value has been enabled.
+# 2. The selected PYTHON_SINGLE_TARGET value is enabled in PYTHON_TARGETS.
 #
 # This expression should be utilized in an ebuild by including it in
 # REQUIRED_USE, optionally behind a use flag.
@@ -191,20 +193,23 @@ EXPORT_FUNCTIONS pkg_setup
 #
 # Example value:
 # @CODE
+# python_single_target_python2_7? ( python_targets_python2_7 )
+# python_single_target_python3_3? ( python_targets_python3_3 )
 # ^^ ( python_single_target_python2_7 python_single_target_python3_3 )
 # @CODE
 
 _python_single_set_globals() {
 	_python_set_impls
 
+	local flags_mt=( "${_PYTHON_SUPPORTED_IMPLS[@]/#/python_targets_}" )
 	local flags=( "${_PYTHON_SUPPORTED_IMPLS[@]/#/python_single_target_}" )
 
 	if [[ ${#_PYTHON_SUPPORTED_IMPLS[@]} -eq 1 ]]; then
 		# if only one implementation is supported, use IUSE defaults
 		# to avoid requesting the user to enable it
-		IUSE="+${flags[0]}"
+		IUSE="+${flags_mt[0]} +${flags[0]}"
 	else
-		IUSE="${flags[*]}"
+		IUSE="${flags_mt[*]} ${flags[*]}"
 	fi
 
 	local requse="^^ ( ${flags[*]} )"
@@ -213,6 +218,11 @@ _python_single_set_globals() {
 
 	local deps= i PYTHON_PKG_DEP
 	for i in "${_PYTHON_SUPPORTED_IMPLS[@]}"; do
+		# The chosen targets need to be in PYTHON_TARGETS as well.
+		# This is in order to enforce correct dependencies on packages
+		# supporting multiple implementations.
+		requse+=" python_single_target_${i}? ( python_targets_${i} )"
+
 		python_export "${i}" PYTHON_PKG_DEP
 		# 1) well, python-exec would suffice as an RDEP
 		# but no point in making this overcomplex, BDEP doesn't hurt anyone
@@ -480,6 +490,15 @@ python_setup() {
 				die "More than one implementation in PYTHON_SINGLE_TARGET."
 			fi
 
+			if ! use "python_targets_${impl}"; then
+				eerror "The implementation chosen as PYTHON_SINGLE_TARGET must be added"
+				eerror "to PYTHON_TARGETS as well. This is in order to ensure that"
+				eerror "dependencies are satisfied correctly. We're sorry"
+				eerror "for the inconvenience."
+				echo
+				die "Build target (${impl}) not in PYTHON_TARGETS."
+			fi
+
 			python_export "${impl}" EPYTHON PYTHON
 			python_wrapper_setup
 		fi
@@ -492,7 +511,7 @@ python_setup() {
 		eerror
 		eerror "${_PYTHON_SUPPORTED_IMPLS[@]}"
 		echo
-		die "No supported Python implementation in PYTHON_SINGLE_TARGET."
+		die "No supported Python implementation in PYTHON_SINGLE_TARGET/PYTHON_TARGETS."
 	fi
 }