distutils-r1.eclass: Introduce DISTUTILS_USE_PEP517=no mode

Introduce a new DISTUTILS_USE_PEP517 value "no" that stands for
"no build system".  This is primarily meant to replace the legacy
distutils-r1 logic used for bootstrapping baseline PEP 517 packages.
At the same time, it provides a convenient replacement for some
of the uses of python-r1.

In this mode, the eclass does not add PEP517-specific dependencies
and does not export default python_compile() and python_install()
implementations.  However, it does set dependencies, REQUIRED_USE
and enables sub-phase usage (with respect to DISTUTILS_OPTIONAL).
It also permits using distutils_enable_{sphinx,tests}.

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

1 files changed, 29 insertions, 1 deletions

diff --git a/eclass/distutils-r1.eclass b/eclass/distutils-r1.eclass
index 208bd2718cb8..30f7d941f0d4 100644
--- a/eclass/distutils-r1.eclass
+++ b/eclass/distutils-r1.eclass
@@ -106,6 +106,8 @@ esac
 #
 # - maturin - maturin backend
 #
+# - no - no PEP517 build system (see below)
+#
 # - pbr - pbr backend
 #
 # - pdm - pdm.pep517 backend
@@ -121,6 +123,17 @@ esac
 #
 # The variable needs to be set before the inherit line.  The eclass
 # adds appropriate build-time dependencies and verifies the value.
+#
+# The special value "no" indicates that the package has no build system.
+# This is not equivalent to unset DISTUTILS_USE_PEP517 (legacy mode).
+# It causes the eclass not to include any build system dependencies
+# and to disable default python_compile() and python_install()
+# implementations.  Baseline Python deps and phase functions will still
+# be set (depending on the value of DISTUTILS_OPTIONAL).  Most of
+# the other eclass functions will work.  Testing venv will be provided
+# in ${BUILD_DIR}/install after python_compile(), and if any (other)
+# files are found in ${BUILD_DIR}/install after python_install(), they
+# will be merged into ${D}.
 
 # @ECLASS_VARIABLE: DISTUTILS_USE_SETUPTOOLS
 # @DEFAULT_UNSET
@@ -212,6 +225,10 @@ _distutils_set_globals() {
 				bdep+='
 					>=dev-util/maturin-0.12.7[${PYTHON_USEDEP}]'
 				;;
+			no)
+				# undo the generic deps added above
+				bdep=
+				;;
 			pbr)
 				bdep+='
 					>=dev-python/pbr-5.8.0-r1[${PYTHON_USEDEP}]'
@@ -789,7 +806,7 @@ distutils_install_for_testing() {
 distutils_write_namespace() {
 	debug-print-function ${FUNCNAME} "${@}"
 
-	if [[ ! ${DISTUTILS_USE_PEP517} ]]; then
+	if [[ ! ${DISTUTILS_USE_PEP517:-no} != no ]]; then
 		die "${FUNCNAME} is available only in PEP517 mode"
 	fi
 	if [[ ${EBUILD_PHASE} != test || ! ${BUILD_DIR} ]]; then
@@ -912,6 +929,9 @@ _distutils-r1_print_package_versions() {
 					dev-util/maturin
 				)
 				;;
+			no)
+				return
+				;;
 			pbr)
 				packages+=(
 					dev-python/pbr
@@ -1207,6 +1227,10 @@ distutils_pep517_install() {
 	debug-print-function ${FUNCNAME} "${@}"
 	[[ ${#} -eq 1 ]] || die "${FUNCNAME} takes exactly one argument: root"
 
+	if [[ ! ${DISTUTILS_USE_PEP517:-no} != no ]]; then
+		die "${FUNCNAME} is available only in PEP517 mode"
+	fi
+
 	local root=${1}
 	local -x WHEEL_BUILD_DIR=${BUILD_DIR}/wheel
 	mkdir -p "${WHEEL_BUILD_DIR}" || die
@@ -1351,6 +1375,9 @@ distutils-r1_python_compile() {
 			in_iuse debug && use debug &&
 				MATURIN_PEP517_ARGS+=" --cargo-extra-args=--profile=dev"
 			;;
+		no)
+			return
+			;;
 	esac
 
 	if [[ ${DISTUTILS_USE_PEP517} ]]; then
@@ -1472,6 +1499,7 @@ distutils-r1_python_test() {
 distutils-r1_python_install() {
 	debug-print-function ${FUNCNAME} "${@}"
 
+	[[ ${DISTUTILS_USE_PEP517} == no ]] && return
 	_python_check_EPYTHON
 
 	local scriptdir=${EPREFIX}/usr/bin