python*r1.eclass: Reliably allow empty <pattern>s to gen funcs

Reliably allow empty pattern lists (equivalent to no restrictions)
in all pattern-based generator functions, notably python_gen_cond_dep.
Previously, only some of the functions accepted them while others
failed via _python_impl_matches function.

Signed-off-by: Michał Górny <mgorny@gentoo.org>

eclass/python-single-r1.eclass

@@ -252,7 +252,7 @@ if [[ ! ${_PYTHON_SINGLE_R1} ]]; then
 
 # @FUNCTION: _python_gen_usedep
 # @INTERNAL
-# @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
@@ -327,7 +327,7 @@ 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
@@ -364,7 +364,7 @@ python_gen_useflags() {
 }
 
 # @FUNCTION: python_gen_cond_dep
-# @USAGE: <dependency> <pattern> [...]
+# @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
@@ -463,9 +463,8 @@ python_gen_impl_dep() {
 	local PYTHON_REQ_USE=${1}
 	shift
 
-	local patterns=( "${@-*}" )
 	for impl in "${_PYTHON_SUPPORTED_IMPLS[@]}"; do
-		if _python_impl_matches "${impl}" "${patterns[@]}"; then
+		if _python_impl_matches "${impl}" "${@}"; then
 			local PYTHON_PKG_DEP
 			python_export "${impl}" PYTHON_PKG_DEP
 			matches+=( "python_single_target_${impl}? ( ${PYTHON_PKG_DEP} )" )