python-r1.eclass: Inline implementation loop logic into python_setup

Inline the logic needed to iterate over implementations directly into
python_setup instead of using python_foreach_impl. This is mostly NFC,
except that we iterate in reverse order now -- that is, we start at
the newest implementation and stop at the first one that works for us.
Previously we (implicitly) started at the oldest implementation, checked
all implementation and used the last one (i.e. the newest) that worked.

More importantly, the new code makes it possible to alter the logic more
easily and avoid relying on implementation of python_foreach_impl().

1 files changed, 26 insertions, 9 deletions

diff --git a/eclass/python-r1.eclass b/eclass/python-r1.eclass
index ae9e3806e729..9c37a20f7c2e 100644
--- a/eclass/python-r1.eclass
+++ b/eclass/python-r1.eclass
@@ -597,16 +597,34 @@ python_foreach_impl() {
 python_setup() {
 	debug-print-function ${FUNCNAME} "${@}"
 
-	local best_impl patterns=( "${@-*}" )
-	_python_try_impl() {
-		if _python_impl_matches "${EPYTHON}" "${patterns[@]}"; then
-			best_impl=${EPYTHON}
+	_python_validate_useflags
+	local pycompat=( "${PYTHON_COMPAT[@]}" )
+	if [[ ${PYTHON_COMPAT_OVERRIDE} ]]; then
+		pycompat=( ${PYTHON_COMPAT_OVERRIDE} )
+	fi
+
+	# (reverse iteration -- newest impl first)
+	local found
+	for (( i = ${#_PYTHON_SUPPORTED_IMPLS[@]} - 1; i >= 0; i-- )); do
+		local impl=${_PYTHON_SUPPORTED_IMPLS[i]}
+
+		# check PYTHON_COMPAT[_OVERRIDE]
+		has "${impl}" "${pycompat[@]}" || continue
+
+		# match USE flags only if override is not in effect
+		if [[ ! ${PYTHON_COMPAT_OVERRIDE} ]]; then
+			use "python_targets_${impl}" || continue
 		fi
-	}
-	python_foreach_impl _python_try_impl
-	unset -f _python_try_impl
 
-	if [[ ! ${best_impl} ]]; then
+		# check patterns
+		_python_impl_matches "${impl}" "${@-*}" || continue
+
+		python_export "${impl}" EPYTHON PYTHON
+		found=1
+		break
+	done
+
+	if [[ ! ${found} ]]; then
 		eerror "${FUNCNAME}: none of the enabled implementation matched the patterns."
 		eerror "  patterns: ${@-'(*)'}"
 		eerror "Likely a REQUIRED_USE constraint (possibly USE-conditional) is missing."
@@ -615,7 +633,6 @@ python_setup() {
 		die "${FUNCNAME}: no enabled implementation satisfy requirements"
 	fi
 
-	python_export "${best_impl}" EPYTHON PYTHON
 	python_wrapper_setup
 }