distutils-r1.eclass: Support GPEP517_TESTING mode

Support GPEP517_TESTING variable to enable using dev-python/gpep517
instead of inline Python snippets.  This is meant to provide
the necessary testing before we stabilize it and switch over.

Closes: gentoo#24910
Signed-off-by: Michał Górny <[email protected]>

eclass/distutils-r1.eclass

@@ -153,6 +153,13 @@ esac
 # ${DISTUTILS_DEPS}"
 # @CODE
 
+# @ECLASS_VARIABLE: GPEP517_TESTING
+# @USER_VARIABLE
+# @DESCRIPTION:
+# Enable in make.conf to test building via dev-python/gpep517 instead of
+# inline Python snippets. dev-python/gpep517 needs to be installed
+# first.
+
 if [[ ! ${_DISTUTILS_R1} ]]; then
 
 [[ ${EAPI} == 6 ]] && inherit eutils xdg-utils
@@ -947,16 +954,20 @@ _distutils-r1_get_backend() {
  if [[ -f pyproject.toml ]]; then
  # if pyproject.toml exists, try getting the backend from it
  # NB: this could fail if pyproject.toml doesn't list one
- build_backend=$(
- "${EPYTHON}" - 3>&1 <<-EOF
- import os
- import tomli
- print(tomli.load(open("pyproject.toml", "rb"))
- .get("build-system", {})
- .get("build-backend", ""),
- file=os.fdopen(3, "w"))
- EOF
- )
+ if [[ ${GPEP517_TESTING} ]]; then
+ build_backend=$(gpep517 get-backend)
+ else
+ build_backend=$(
+ "${EPYTHON}" - 3>&1 <<-EOF
+ import os
+ import tomli
+ print(tomli.load(open("pyproject.toml", "rb"))
+ .get("build-system", {})
+ .get("build-backend", ""),
+ file=os.fdopen(3, "w"))
+ EOF
+ )
+ fi
  fi
  if [[ -z ${build_backend} && ${DISTUTILS_USE_PEP517} == setuptools &&
  -f setup.py ]]
@@ -1022,30 +1033,45 @@ distutils_pep517_install() {
 
  local build_backend=$(_distutils-r1_get_backend)
  einfo " Building the wheel for ${PWD#${WORKDIR}/} via ${build_backend}"
- local wheel=$(
- "${EPYTHON}" - 3>&1 >&2 <<-EOF || die "Wheel build failed"
- import ${build_backend%:*}
- import os
- print(${build_backend/:/.}.build_wheel(os.environ['WHEEL_BUILD_DIR']),
- file=os.fdopen(3, 'w'))
- EOF
- )
+ if [[ ${GPEP517_TESTING} ]]; then
+ local wheel=$(
+ gpep517 build-wheel --backend "${build_backend}" \
+ --output-fd 3 \
+ --wheel-dir "${WHEEL_BUILD_DIR}" 3>&1 >&2 ||
+ die "Wheel build failed"
+ )
+ else
+ local wheel=$(
+ "${EPYTHON}" - 3>&1 >&2 <<-EOF || die "Wheel build failed"
+ import ${build_backend%:*}
+ import os
+ print(${build_backend/:/.}.build_wheel(os.environ['WHEEL_BUILD_DIR']),
+ file=os.fdopen(3, 'w'))
+ EOF
+ )
+ fi
  [[ -n ${wheel} ]] || die "No wheel name returned"
 
  einfo " Installing the wheel to ${root}"
- # NB: --compile-bytecode does not produce the correct paths,
- # and python_optimize doesn't handle being called outside D,
- # so we just defer compiling until the final merge
- # NB: we override sys.prefix & sys.exec_prefix because otherwise
- # installer would use virtualenv's prefix
- local -x PYTHON_PREFIX=${EPREFIX}/usr
- "${EPYTHON}" - -d "${root}" "${WHEEL_BUILD_DIR}/${wheel}" --no-compile-bytecode \
- <<-EOF || die "installer failed"
- import os, sys
- sys.prefix = sys.exec_prefix = os.environ["PYTHON_PREFIX"]
- from installer.__main__ import main
- main(sys.argv[1:])
- EOF
+ if [[ ${GPEP517_TESTING} ]]; then
+ gpep517 install-wheel --destdir="${root}" --interpreter="${PYTHON}" \
+ --prefix="${EPREFIX}/usr" "${WHEEL_BUILD_DIR}/${wheel}" ||
+ die "Wheel install failed"
+ else
+ # NB: --compile-bytecode does not produce the correct paths,
+ # and python_optimize doesn't handle being called outside D,
+ # so we just defer compiling until the final merge
+ # NB: we override sys.prefix & sys.exec_prefix because otherwise
+ # installer would use virtualenv's prefix
+ local -x PYTHON_PREFIX=${EPREFIX}/usr
+ "${EPYTHON}" - -d "${root}" "${WHEEL_BUILD_DIR}/${wheel}" --no-compile-bytecode \
+ <<-EOF || die "installer failed"
+ import os, sys
+ sys.prefix = sys.exec_prefix = os.environ["PYTHON_PREFIX"]
+ from installer.__main__ import main
+ main(sys.argv[1:])
+ EOF
+ fi
 
  # remove installed licenses
  find "${root}$(python_get_sitedir)" \