Re: [PR PATCH] [Updated] [RFC, WIP] common/build-helper/meson.sh: new build helper, used by meson build style

[ahesford <ahesford@users.noreply.github.com>]

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There is an updated pull request by ahesford against master on the void-packages repository

https://github.com/ahesford/void-packages meson
https://github.com/void-linux/void-packages/pull/46117

[RFC, WIP] common/build-helper/meson.sh: new build helper, used by meson build style
The `python3-scipy` package now builds with `python3-meson-python`, with some more coming down the pike. The Python build process is necessary to include Python package metadata. For SciPy, this is accomplished by using the `meson` build style to configure a build directory, then overriding `do_build` and `do_install` to build things the PEP517 way (using the pre-configured build directory).

It might be helpful to define a `meson` build helper that can write out the standard cross file for builds, allowing packages like SciPy to use the `python3-pep517` build style with the `meson` helper. There are some issues to be worked out:
1. It seems like the `xbps_meson.cross` is written before `CFLAGS`, *et al.* are properly defined, so this cross file is actually broken. (This is the process by which the `qmake` helper writes its configurations, and they reference `CFLAGS` and others; is the `qmake` helper writing broken configs?)
2. The meson configuration (which would need to happen even with `python3-pep517` plus a `meson` helper) still includes a lot of magic that would have to be brought over to templates. This isn't really easier than the current practice of overriding the one-line `do_build` and `do_install`.

A possible solution would be to define a special-purpose function in the helper, called `vmesoncross` or somesuch, that will only write the configured when called---from a build function where these are properly defined (*e.g.*, `pre_configure`, `do_configure`). We could also define a special `do_configure`-like function in the helper that can be used by the `meson` style to actually do the configuration. This might be a bit ugly, but avoids repetition or violating the typical practice that the actual build functions are only defined in templates or build styles.

A third option is just defining a new `python3-meson` build style that mashes the meson `do_configure` bits from the `meson` style with the `do_build` and `do_install` bits from the `python3-pep517` style.

All of these options are sub-optimal, but I'm not sure which one is least offsensive.

A patch file from https://github.com/void-linux/void-packages/pull/46117.patch is attached

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From 5dbb797c644dac784e31d29aa1590d2d9a5b20d8 Mon Sep 17 00:00:00 2001
From: "Andrew J. Hesford" <ajh@sideband.org>
Date: Mon, 18 Sep 2023 15:40:49 -0400
Subject: [PATCH 1/3] common/build-helper/meson.sh: new build helper, used by
 meson build style

---
 common/build-helper/meson.sh            | 82 ++++++++++++++++++++++++
 common/build-style/meson.sh             | 85 +------------------------
 common/environment/build-style/meson.sh |  1 +
 3 files changed, 84 insertions(+), 84 deletions(-)
 create mode 100644 common/build-helper/meson.sh

diff --git a/common/build-helper/meson.sh b/common/build-helper/meson.sh
new file mode 100644
index 0000000000000..1933306c18a4b
--- /dev/null
+++ b/common/build-helper/meson.sh
@@ -0,0 +1,82 @@
+# This bulid-helper writes a Meson cross-file, allowing other build styles
+# to properly drive cross-builds in Meson when appropriate
+
+if [ "$CROSS_BUILD" ]; then
+	mkdir -p "${XBPS_WRAPPERDIR}/meson"
+
+	_MESON_TARGET_ENDIAN=little
+	# drop the -musl suffix to the target cpu, meson doesn't recognize it
+	_MESON_TARGET_CPU=${XBPS_TARGET_MACHINE/-musl/}
+	case "$XBPS_TARGET_MACHINE" in
+		mips|mips-musl|mipshf-musl)
+			_MESON_TARGET_ENDIAN=big
+			_MESON_CPU_FAMILY=mips
+			;;
+		armv*)
+			_MESON_CPU_FAMILY=arm
+			;;
+		i686*)
+			_MESON_CPU_FAMILY=x86
+			;;
+		ppc64le*)
+			_MESON_CPU_FAMILY=ppc64
+			;;
+		ppc64*)
+			_MESON_TARGET_ENDIAN=big
+			_MESON_CPU_FAMILY=ppc64
+			;;
+		ppcle*)
+			_MESON_CPU_FAMILY=ppc
+			;;
+		ppc*)
+			_MESON_TARGET_ENDIAN=big
+			_MESON_CPU_FAMILY=ppc
+			;;
+		*)
+			# if we reached here that means that the cpu and cpu_family
+			# are the same like 'x86_64' and 'aarch64'
+			_MESON_CPU_FAMILY=${_MESON_TARGET_CPU}
+			;;
+	esac
+
+	# Tell meson to run binaries with qemu if desired
+	_MESON_EXE_WRAPPER=""
+	if [[ "${build_helper}" = *qemu* ]]; then
+		_MESON_EXE_WRAPPER="exe_wrapper = '/usr/bin/qemu-${XBPS_TARGET_QEMU_MACHINE}-static'"
+	fi
+
+	# Record cross-compiling information in cross file.
+	#
+	# CFLAGS, CXXFLAGS and LDFLAGS are not yet available and
+	# will be taken from the environment at configure time.
+	cat > "${XBPS_WRAPPERDIR}/meson/xbps_meson.cross" <<-EOF
+		[binaries]
+		${_MESON_EXE_WRAPPER:-# exe_wrapper is not set}
+		c = '${CC}'
+		cpp = '${CXX}'
+		ar = '${XBPS_CROSS_TRIPLET}-gcc-ar'
+		nm = '${NM}'
+		ld = '${LD}'
+		strip = '${STRIP}'
+		readelf = '${READELF}'
+		objcopy = '${OBJCOPY}'
+		pkgconfig = '${PKG_CONFIG}'
+		rust = ['rustc', '--target', '${RUST_TARGET}' ,'--sysroot', '${XBPS_CROSS_BASE}/usr']
+		g-ir-scanner = '${XBPS_CROSS_BASE}/usr/bin/g-ir-scanner'
+		g-ir-compiler = '${XBPS_CROSS_BASE}/usr/bin/g-ir-compiler'
+		g-ir-generate = '${XBPS_CROSS_BASE}/usr/bin/g-ir-generate'
+		llvm-config = '/usr/bin/llvm-config'
+		cups-config = '${XBPS_CROSS_BASE}/usr/bin/cups-config'
+		
+		[properties]
+		needs_exe_wrapper = true
+		
+		[host_machine]
+		system = 'linux'
+		cpu_family = '${_MESON_CPU_FAMILY}'
+		cpu = '${_MESON_TARGET_CPU}'
+		endian = '${_MESON_TARGET_ENDIAN}'
+		EOF
+
+	unset _MESON_CPU_FAMILY _MESON_TARGET_CPU _MESON_TARGET_ENDIAN _MESON_EXE_WRAPPER
+fi
diff --git a/common/build-style/meson.sh b/common/build-style/meson.sh
index e983c5f42c2f7..5ea2eeda40097 100644
--- a/common/build-style/meson.sh
+++ b/common/build-style/meson.sh
@@ -1,94 +1,11 @@
 #
 # This helper is for templates using meson.
 #
-do_patch() {
-	: ${meson_crossfile:=xbps_meson.cross}
-
-	if [ "$CROSS_BUILD" ]; then
-		_MESON_TARGET_ENDIAN=little
-		# drop the -musl suffix to the target cpu, meson doesn't recognize it
-		_MESON_TARGET_CPU=${XBPS_TARGET_MACHINE/-musl/}
-		case "$XBPS_TARGET_MACHINE" in
-			mips|mips-musl|mipshf-musl)
-				_MESON_TARGET_ENDIAN=big
-				_MESON_CPU_FAMILY=mips
-				;;
-			armv*)
-				_MESON_CPU_FAMILY=arm
-				;;
-			i686*)
-				_MESON_CPU_FAMILY=x86
-				;;
-			ppc64le*)
-				_MESON_CPU_FAMILY=ppc64
-				;;
-			ppc64*)
-				_MESON_TARGET_ENDIAN=big
-				_MESON_CPU_FAMILY=ppc64
-				;;
-			ppcle*)
-				_MESON_CPU_FAMILY=ppc
-				;;
-			ppc*)
-				_MESON_TARGET_ENDIAN=big
-				_MESON_CPU_FAMILY=ppc
-				;;
-			*)
-				# if we reached here that means that the cpu and cpu_family
-				# are the same like 'x86_64' and 'aarch64'
-				_MESON_CPU_FAMILY=${_MESON_TARGET_CPU}
-				;;
-		esac
-
-		# Record cross-compiling information in cross file.
-		# CFLAGS and LDFLAGS must be set as c_args and c_link_args.
-		cat > ${meson_crossfile} <<EOF
-[binaries]
-c = '${CC}'
-cpp = '${CXX}'
-ar = '${XBPS_CROSS_TRIPLET}-gcc-ar'
-nm = '${NM}'
-ld = '${LD}'
-strip = '${STRIP}'
-readelf = '${READELF}'
-objcopy = '${OBJCOPY}'
-pkgconfig = '${PKG_CONFIG}'
-rust = ['rustc', '--target', '${RUST_TARGET}' ,'--sysroot', '${XBPS_CROSS_BASE}/usr']
-g-ir-scanner = '${XBPS_CROSS_BASE}/usr/bin/g-ir-scanner'
-g-ir-compiler = '${XBPS_CROSS_BASE}/usr/bin/g-ir-compiler'
-g-ir-generate = '${XBPS_CROSS_BASE}/usr/bin/g-ir-generate'
-llvm-config = '/usr/bin/llvm-config'
-cups-config = '${XBPS_CROSS_BASE}/usr/bin/cups-config'
-
-[properties]
-needs_exe_wrapper = true
-
-[built-in options]
-c_args = ['$(echo ${CFLAGS} | sed -r "s/\s+/','/g")']
-c_link_args = ['$(echo ${LDFLAGS} | sed -r "s/\s+/','/g")']
-
-cpp_args = ['$(echo ${CXXFLAGS} | sed -r "s/\s+/','/g")']
-cpp_link_args = ['$(echo ${LDFLAGS} | sed -r "s/\s+/','/g")']
-
-[host_machine]
-system = 'linux'
-cpu_family = '${_MESON_CPU_FAMILY}'
-cpu = '${_MESON_TARGET_CPU}'
-endian = '${_MESON_TARGET_ENDIAN}'
-EOF
-		if [[ $build_helper = *"qemu"* ]]; then
-			sed -e "/\[binaries\]/ a exe_wrapper = '/usr/bin/qemu-${XBPS_TARGET_QEMU_MACHINE}-static'" \
-				-i ${meson_crossfile}
-		fi
-
-		unset _MESON_CPU_FAMILY _MESON_TARGET_CPU _MESON_TARGET_ENDIAN
-	fi
-}
 
 do_configure() {
 	: ${meson_cmd:=meson}
 	: ${meson_builddir:=build}
-	: ${meson_crossfile:=xbps_meson.cross}
+	: ${meson_crossfile:="${XBPS_WRAPPERDIR}/meson/xbps_meson.cross"}
 
 	if [ "$CROSS_BUILD" ]; then
 		configure_args+=" --cross-file=${meson_crossfile}"
diff --git a/common/environment/build-style/meson.sh b/common/environment/build-style/meson.sh
index d5a3c4141f7d9..dbfe93700f691 100644
--- a/common/environment/build-style/meson.sh
+++ b/common/environment/build-style/meson.sh
@@ -1 +1,2 @@
 hostmakedepends+=" meson"
+build_helper+=" meson"

From a640b681dd99188880ee6704c35f9fa9b851f6a3 Mon Sep 17 00:00:00 2001
From: "Andrew J. Hesford" <ajh@sideband.org>
Date: Wed, 20 Sep 2023 10:45:43 -0400
Subject: [PATCH 2/3] python3-scipy: use new meson helper

---
 srcpkgs/python3-scipy/template | 47 ++++++++++++++++------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/srcpkgs/python3-scipy/template b/srcpkgs/python3-scipy/template
index ba0dd761cdcf5..e99919babf3bf 100644
--- a/srcpkgs/python3-scipy/template
+++ b/srcpkgs/python3-scipy/template
@@ -2,9 +2,10 @@
 pkgname=python3-scipy
 version=1.11.2
 revision=1
-build_style=meson
-build_helper="python3"
-configure_args="$(vopt_if openblas "" "-Dblas=blas -Dlapack=lapack")"
+build_style=python3-pep517
+build_helper="meson"
+make_build_args="--no-isolation --wheel
+ $(vopt_if openblas "" "-Csetup-args=-Dblas=blas -Csetup-args=-Dlapack=lapack")"
 hostmakedepends="python3-build python3-installer python3-meson-python
  python3-wheel python3-Cython python3-pybind11 pythran python3-numpy
  gcc-fortran pkg-config"
@@ -22,8 +23,12 @@ make_check="no" # Tests need an installed copy to run and meson makes this tough
 build_options="openblas"
 
 if [ "$CROSS_BUILD" ]; then
+	make_build_args+="
+	 -Csetup-args=--cross-file=${XBPS_WRAPPERDIR}/meson/xbps_meson.cross
+	 -Csetup-args=--cross-file=${XBPS_WRAPPERDIR}/meson/python.cross
+	"
+
 	_pybind11_dir="${py3_sitelib}/pybind11"
-	configure_args+=" --cross-file=python.cross"
 	export PKG_CONFIG_PATH="${XBPS_CROSS_BASE}/${_pybind11_dir}/share/pkgconfig"
 	# pybind11 uses a path relative to the pkgconfig file to set $prefix,
 	# which causes the wrapper to double-include $XBPS_CROSS_BASE; override
@@ -46,34 +51,26 @@ if [ "$build_option_openblas" ]; then
 	esac
 fi
 
-pre_patch() {
-	if [ "${CROSS_BUILD}" ]; then
-		# Meson can't tolerate $CC with arguments as set by the build helper
-		CC="${XBPS_CROSS_TRIPLET}-gcc"
-		# CXX needs to know where to find Python headers
-		CXXFLAGS+=" -I${XBPS_CROSS_BASE}/${py3_inc}"
-	fi
-}
-
 post_patch() {
 	if [ "$CROSS_BUILD" ]; then
 		local _xpy="${XBPS_CROSS_BASE}/${py3_sitelib}"
-		cat > python.cross <<-EOF
-		[properties]
-		numpy-include-dir = '${_xpy}/numpy/core/include'
-		pythran-include-dir = '${_xpy}/pythran'
-		EOF
+		cat > "${XBPS_WRAPPERDIR}/meson/python.cross" <<-EOF
+			[properties]
+			numpy-include-dir = '${_xpy}/numpy/core/include'
+			pythran-include-dir = '${_xpy}/pythran'
+			EOF
 	fi
 }
 
-do_build() {
-	# Use the build directory already configured by xbps-src for meson
-	python3 -m build --no-isolation --wheel \
-		-Cbuilddir="./build" -Ccompile-args="${makejobs}" .
+pre_build() {
+	if [ "$CROSS_BUILD" ]; then
+		# Meson can't tolerate $CC with arguments as set by the build helper
+		CC="${XBPS_CROSS_TRIPLET}-gcc"
+		# CXX needs to know where to find Python headers
+		CXXFLAGS+=" -I${XBPS_CROSS_BASE}/${py3_inc}"
+	fi
 }
 
-do_install() {
-	python3 -m installer --destdir "${DESTDIR}" \
-		--no-compile-bytecode dist/*.whl
+post_install() {
 	vlicense LICENSE.txt
 }

From bedace4ff187239e850e30fbb8169a8c13655033 Mon Sep 17 00:00:00 2001
From: "Andrew J. Hesford" <ajh@sideband.org>
Date: Wed, 20 Sep 2023 11:13:02 -0400
Subject: [PATCH 3/3] python3-scikit-image: use new meson helper

---
 srcpkgs/python3-scikit-image/template | 34 +++++++++++----------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/srcpkgs/python3-scikit-image/template b/srcpkgs/python3-scikit-image/template
index e800ed4f00f6c..b19743e50f37d 100644
--- a/srcpkgs/python3-scikit-image/template
+++ b/srcpkgs/python3-scikit-image/template
@@ -2,8 +2,8 @@
 pkgname=python3-scikit-image
 version=0.21.0
 revision=1
-build_style=meson
-build_helper="python3"
+build_style=python3-pep517
+build_helper="meson"
 hostmakedepends="python3-build python3-installer python3-meson-python
  python3-wheel python3-setuptools python3-packaging python3-Cython pythran
  python3-lazy_loader python3-numpy pkg-config"
@@ -21,22 +21,15 @@ checksum=53a82a9dbd3ed608d2ad3876269a271a7e922b12e228388eac996b508aadd652
 make_check=no
 
 if [ "${CROSS_BUILD}" ]; then
-	configure_args="--cross-file=python.cross"
+	make_build_args+=" --no-isolation --wheel
+	 -Csetup-args=--cross-file=${XBPS_WRAPPERDIR}/meson/xbps_meson.cross
+	 -Csetup-args=--cross-file=${XBPS_WRAPPERDIR}/meson/python.cross"
 fi
 
-pre_patch() {
-	if [ "${CROSS_BUILD}" ]; then
-		# Meson can't tolerate $CC with arguments as set by build helper
-		CC="${XBPS_CROSS_TRIPLET}-gcc"
-		# CXX needs to know where to find Python headers
-		CXXFLAGS+=" -I${XBPS_CROSS_BASE}/${py3_inc}"
-	fi
-}
-
 post_patch() {
 	if [ "${CROSS_BUILD}" ]; then
 		local _xpy="${XBPS_CROSS_BASE}/${py3_sitelib}"
-		cat > python.cross <<-EOF
+		cat > "${XBPS_WRAPPERDIR}/meson/python.cross" <<-EOF
 		[properties]
 		numpy-include-dir = '${_xpy}/numpy/core/include'
 		pythran-include-dir = '${_xpy}/pythran'
@@ -44,14 +37,15 @@ post_patch() {
 	fi
 }
 
-do_build() {
-	# Use the build directory already configured by xbps-src for meson
-	python3 -m build --no-isolation --wheel \
-		-Cbuilddir="./build" -Ccompile-args="${makejobs}" .
+pre_build() {
+	if [ "${CROSS_BUILD}" ]; then
+		# Meson can't tolerate $CC with arguments as set by build helper
+		CC="${XBPS_CROSS_TRIPLET}-gcc"
+		# CXX needs to know where to find Python headers
+		CXXFLAGS+=" -I${XBPS_CROSS_BASE}/${py3_inc}"
+	fi
 }
 
-do_install() {
-	python3 -m installer --destdir "${DESTDIR}" \
-		--no-compile-bytecode dist/*.whl
+post_install() {
 	vlicense LICENSE.txt
 }