[gentoo-dev] [PATCH 1/2] eclass: Add first version of lua.eclass

[Marek Szuba]

This eclass should be to Lua what python-r1 is to Python. Indeed, most
of the plumbing has been shamelessly stolen from that eclass.

What works:
 - support for slotted dev-lang/lua
 - building and installing Lua modules, for multiple Lua implementations
 - dependencies on other Lua modules

What doesn't work yet:
 - support for dev-lang/luajit (not in the least because the versions
   currently in the tree share module directories with dev-lang/lua)
 - proper support for building against a single Lua target

Signed-off-by: Marek Szuba <marecki@g.o>
---
 eclass/lua.eclass | 710 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 710 insertions(+)
 create mode 100644 eclass/lua.eclass

diff --git a/eclass/lua.eclass b/eclass/lua.eclass
new file mode 100644
index 00000000000..1b104b31cda
--- /dev/null
+++ b/eclass/lua.eclass
@@ -0,0 +1,710 @@
+# Copyright 1999-2020 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: lua.eclass
+# @MAINTAINER:
+# Marek Szuba <marecki@g.o>
+# @AUTHOR:
+# Marek Szuba <marecki@g.o>
+# Based on python{,-utils}-r1.eclass by Michał Górny <mgorny@g.o> et al.
+# @SUPPORTED_EAPIS: 7
+# @BLURB: A common eclass for Lua packages
+# @DESCRIPTION:
+# A common eclass providing helper functions to build and install
+# packages supporting being installed for multiple Lua implementations.
+#
+# This eclass sets correct IUSE. Modification of REQUIRED_USE has to
+# be done by the author of the ebuild (but LUA_REQUIRED_USE is
+# provided for convenience, see below). The eclass exports LUA_DEPS
+# and LUA_USEDEP so you can create correct dependencies for your
+# package easily. It also provides methods to easily run a command for
+# each enabled Lua implementation and duplicate the sources for them.
+#
+# Please note that for the time being this eclass does NOT support luajit.
+#
+# @EXAMPLE:
+# @CODE
+# EAPI=7
+#
+# LUA_COMPAT=( lua5-{1..3} )
+#
+# inherit lua
+#
+# [...]
+#
+# REQUIRED_USE="${LUA_REQUIRED_USE}"
+# DEPEND="${LUA_DEPS}"
+# RDEPEND="${DEPEND}
+#	dev-lua/foo[${LUA_USEDEP}]"
+# BDEPEND="virtual/pkgconfig"
+#
+# lua_src_install() {
+#	emake LUA_VERSION="$(lua_get_version)" install
+# }
+#
+# src_install() {
+#	lua_foreach_impl lua_src_install
+# }
+# @CODE
+
+case ${EAPI:-0} in
+	0|1|2|3|4|5|6)
+		die "Unsupported EAPI=${EAPI} (too old) for ${ECLASS}"
+		;;
+	7)
+		;;
+	*)
+		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
+		;;
+esac
+
+if [[ ! ${_LUA_R0} ]]; then
+
+inherit multibuild toolchain-funcs
+
+BDEPEND="virtual/pkgconfig"
+
+fi
+
+# @ECLASS-VARIABLE: LUA_COMPAT
+# @REQUIRED
+# @PRE_INHERIT
+# @DESCRIPTION:
+# This variable contains a list of Lua implementations the package
+# supports. It must be set before the `inherit' call. It has to be
+# an array.
+#
+# Example:
+# @CODE
+# LUA_COMPAT=( lua5-1 lua5-2 lua5-3 )
+# @CODE
+#
+# Please note that you can also use bash brace expansion if you like:
+# @CODE
+# LUA_COMPAT=( lua5_{1..3} )
+# @CODE
+
+# @ECLASS-VARIABLE: LUA_COMPAT_OVERRIDE
+# @USER_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# This variable can be used when working with ebuilds to override
+# the in-ebuild LUA_COMPAT. It is a string listing all
+# the implementations which package will be built for. It need be
+# specified in the calling environment, and not in ebuilds.
+#
+# It should be noted that in order to preserve metadata immutability,
+# LUA_COMPAT_OVERRIDE does not affect IUSE nor dependencies.
+# The state of LUA_TARGETS is ignored, and all the implementations
+# in LUA_COMPAT_OVERRIDE are built. Dependencies need to be satisfied
+# manually.
+#
+# Example:
+# @CODE
+# LUA_COMPAT_OVERRIDE='lua5-2' emerge -1v dev-lua/foo
+# @CODE
+
+# @ECLASS-VARIABLE: LUA_REQ_USE
+# @DEFAULT_UNSET
+# @PRE_INHERIT
+# @DESCRIPTION:
+# The list of USE flags required to be enabled on the chosen Lua
+# implementations, formed as a USE-dependency string. It should be valid
+# for all implementations in LUA_COMPAT, so it may be necessary to
+# use USE defaults.
+# This must be set before calling `inherit'.
+#
+# Example:
+# @CODE
+# LUA_REQ_USE="deprecated"
+# @CODE
+#
+# It will cause the Lua dependencies to look like:
+# @CODE
+# lua_targets_luaX-Y? ( dev-lang/lua:X.Y[deprecated] )
+# @CODE
+
+# @ECLASS-VARIABLE: BUILD_DIR
+# @OUTPUT_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# The current build directory. In global scope, it is supposed to
+# contain an initial build directory; if unset, it defaults to ${S}.
+#
+# In functions run by lua_foreach_impl(), the BUILD_DIR is locally
+# set to an implementation-specific build directory. That path is
+# created through appending a hyphen and the implementation name
+# to the final component of the initial BUILD_DIR.
+#
+# Example value:
+# @CODE
+# ${WORKDIR}/foo-1.3-lua5-1
+# @CODE
+
+# @ECLASS-VARIABLE: ELUA
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# The executable name of the current Lua interpreter. This variable is set
+# automatically in functions called by lua_foreach_impl().
+#
+# Example value:
+# @CODE
+# lua5.1
+# @CODE
+
+# @ECLASS-VARIABLE: LUA
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# The absolute path to the current Lua interpreter. This variable is set
+# automatically in functions called by lua_foreach_impl().
+#
+# Example value:
+# @CODE
+# /usr/bin/lua5.1
+# @CODE
+
+# @ECLASS-VARIABLE: LUA_DEPS
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# This is an eclass-generated Lua dependency string for all
+# implementations listed in LUA_COMPAT.
+#
+# Example use:
+# @CODE
+# RDEPEND="${LUA_DEPS}
+#   dev-foo/mydep"
+# DEPEND="${RDEPEND}"
+# @CODE
+#
+# Example value:
+# @CODE
+# lua_targets_lua5-1? ( dev-lang/lua:5.1 )
+# lua_targets_lua5-2? ( dev-lang/lua:5.2 )
+# @CODE
+
+# @ECLASS-VARIABLE: LUA_REQUIRED_USE
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# This is an eclass-generated required-use expression which ensures at
+# least one Lua implementation has been enabled.
+#
+# This expression should be utilized in an ebuild by including it in
+# REQUIRED_USE, optionally behind a use flag.
+#
+# Example use:
+# @CODE
+# REQUIRED_USE="lua? ( ${LUA_REQUIRED_USE} )"
+# @CODE
+#
+# Example value:
+# @CODE
+# || ( lua_targets_lua5-1 lua_targets_lua5-2 )
+# @CODE
+
+# @ECLASS-VARIABLE: LUA_USEDEP
+# @OUTPUT_VARIABLE
+# @DESCRIPTION:
+# This is an eclass-generated USE-dependency string which can be used to
+# depend on another Lua package being built for the same Lua
+# implementations.
+#
+# Example use:
+# @CODE
+# RDEPEND="dev-lua/foo[${LUA_USEDEP}]"
+# @CODE
+#
+# Example value:
+# @CODE
+# lua_targets_lua5-1(-)?,lua_targets_lua5-2(-)?
+# @CODE
+
+if [[ ! ${_LUA_R0} ]]; then
+
+# @FUNCTION: _lua_export
+# @USAGE: [<impl>] <variables>...
+# @INTERNAL
+# @DESCRIPTION:
+# Set and export the Lua implementation-relevant variables passed
+# as parameters.
+#
+# The optional first parameter may specify the requested Lua
+# implementation (either as LUA_TARGETS value, e.g. lua5-2,
+# or an ELUA one, e.g. lua5.2). If no implementation passed,
+# the current one will be obtained from ${ELUA}.
+_lua_export() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local impl var
+
+	case "${1}" in
+		lua*)
+			impl=${1/-/.}
+			shift
+			;;
+		*)
+			impl=${ELUA}
+			if [[ -z ${impl} ]]; then
+				die "_lua_export called without a Lua implementation and ELUA is unset"
+			fi
+			;;
+	esac
+	debug-print "${FUNCNAME}: implementation: ${impl}"
+
+	for var; do
+		case "${var}" in
+			ELUA)
+				export ELUA=${impl}
+				debug-print "${FUNCNAME}: ELUA = ${ELUA}"
+				;;
+			LUA)
+				export LUA="${EPREFIX}"/usr/bin/${impl}
+				debug-print "${FUNCNAME}: LUA = ${LUA}"
+				;;
+			LUA_CFLAGS)
+				local val
+
+				val=$($(tc-getPKG_CONFIG) --cflags ${impl}) || die
+
+				export LUA_CFLAGS=${val}
+				debug-print "${FUNCNAME}: LUA_CFLAGS = ${LUA_CFLAGS}"
+				;;
+			LUA_CMOD_DIR)
+				local val
+
+				val=$($(tc-getPKG_CONFIG) --variable INSTALL_CMOD ${impl}) || die
+
+				export LUA_CMOD_DIR=${val}
+				debug-print "${FUNCNAME}: LUA_CMOD_DIR = ${LUA_CMOD_DIR}"
+				;;
+			LUA_LIBS)
+				local val
+
+				val=$($(tc-getPKG_CONFIG) --libs ${impl}) || die
+
+				export LUA_LIBS=${val}
+				debug-print "${FUNCNAME}: LUA_LIBS = ${LUA_LIBS}"
+				;;
+			LUA_LMOD_DIR)
+				local val
+
+				val=$($(tc-getPKG_CONFIG) --variable INSTALL_LMOD ${impl}) || die
+
+				export LUA_LMOD_DIR=${val}
+				debug-print "${FUNCNAME}: LUA_LMOD_DIR = ${LUA_LMOD_DIR}"
+				;;
+			LUA_PKG_DEP)
+				local d
+				case ${impl} in
+					lua*)
+						LUA_PKG_DEP="dev-lang/lua:${impl#lua}"
+						;;
+					*)
+						die "Invalid implementation: ${impl}"
+						;;
+				esac
+
+				# use-dep
+				if [[ ${LUA_REQ_USE} ]]; then
+					LUA_PKG_DEP+=[${LUA_REQ_USE}]
+				fi
+
+				export LUA_PKG_DEP
+				debug-print "${FUNCNAME}: LUA_PKG_DEP = ${LUA_PKG_DEP}"
+				;;
+			LUA_VERSION)
+				local val
+
+				val=$($(tc-getPKG_CONFIG) --modversion ${impl}) || die
+
+				export LUA_VERSION=${val}
+				debug-print "${FUNCNAME}: LUA_VERSION = ${LUA_VERSION}"
+				;;
+			*)
+				die "_lua_export: unknown variable ${var}"
+				;;
+		esac
+	done
+}
+
+# @FUNCTION: _lua_validate_useflags
+# @INTERNAL
+# @DESCRIPTION:
+# Enforce the proper setting of LUA_TARGETS, if LUA_COMPAT_OVERRIDE
+# is not in effect. If it is, just warn that the flags will be ignored.
+_lua_validate_useflags() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ ${LUA_COMPAT_OVERRIDE} ]]; then
+		if [[ ! ${_LUA_COMPAT_OVERRIDE_WARNED} ]]; then
+			ewarn "WARNING: LUA_COMPAT_OVERRIDE in effect. The following Lua"
+			ewarn "implementations will be enabled:"
+			ewarn
+			ewarn "	${LUA_COMPAT_OVERRIDE}"
+			ewarn
+			ewarn "Dependencies won't be satisfied, and LUA_TARGETS will be ignored."
+			_LUA_COMPAT_OVERRIDE_WARNED=1
+		fi
+		# we do not use flags with LCO
+		return
+	fi
+
+	local i
+
+	for i in "${_LUA_SUPPORTED_IMPLS[@]}"; do
+		use "lua_targets_${i}" && return 0
+	done
+
+	eerror "No Lua implementation selected for the build. Please add one"
+	eerror "of the following values to your LUA_TARGETS (in make.conf):"
+	eerror
+	eerror "${LUA_COMPAT[@]}"
+	echo
+	die "No supported Lua implementation in LUA_TARGETS."
+}
+
+# @FUNCTION: _lua_obtain_impls
+# @INTERNAL
+# @DESCRIPTION:
+# Set up the enabled implementation list.
+_lua_obtain_impls() {
+	_lua_validate_useflags
+
+	if [[ ${LUA_COMPAT_OVERRIDE} ]]; then
+		MULTIBUILD_VARIANTS=( ${LUA_COMPAT_OVERRIDE} )
+		return
+	fi
+
+	MULTIBUILD_VARIANTS=()
+
+	local impl
+	for impl in "${_LUA_SUPPORTED_IMPLS[@]}"; do
+		has "${impl}" "${LUA_COMPAT[@]}" && \
+		use "lua_targets_${impl}" && MULTIBUILD_VARIANTS+=( "${impl}" )
+	done
+}
+
+
+# @FUNCTION: _lua_multibuild_wrapper
+# @USAGE: <command> [<args>...]
+# @INTERNAL
+# @DESCRIPTION:
+# Initialize the environment for the Lua implementation selected
+# for multibuild.
+_lua_multibuild_wrapper() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local -x ELUA LUA
+	_lua_export "${MULTIBUILD_VARIANT}" ELUA LUA
+	local -x PATH=${PATH} PKG_CONFIG_PATH=${PKG_CONFIG_PATH}
+	_lua_wrapper_setup
+
+	"${@}"
+}
+
+# @FUNCTION: _lua_wrapper_setup
+# @USAGE: [<path> [<impl>]]
+# @INTERNAL
+# @DESCRIPTION:
+# Create proper 'lua' executable and pkg-config wrappers
+# (if available) in the directory named by <path>. Set up PATH
+# and PKG_CONFIG_PATH appropriately. <path> defaults to ${T}/${ELUA}.
+#
+# The wrappers will be created for implementation named by <impl>,
+# or for one named by ${ELUA} if no <impl> passed.
+#
+# If the named directory contains a lua symlink already, it will
+# be assumed to contain proper wrappers already and only environment
+# setup will be done. If wrapper update is requested, the directory
+# shall be removed first.
+_lua_wrapper_setup() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local workdir=${1:-${T}/${ELUA}}
+	local impl=${2:-${ELUA}}
+
+	[[ ${workdir} ]] || die "${FUNCNAME}: no workdir specified."
+	[[ ${impl} ]] || die "${FUNCNAME}: no impl nor ELUA specified."
+
+	if [[ ! -x ${workdir}/bin/lua ]]; then
+		mkdir -p "${workdir}"/{bin,pkgconfig} || die
+
+		# Clean up, in case we were supposed to do a cheap update
+		rm -f "${workdir}"/bin/lua{,c} || die
+		rm -f "${workdir}"/pkgconfig/lua.pc || die
+
+		local ELUA LUA
+		_lua_export "${impl}" ELUA LUA
+
+		# Lua interpreter and compiler
+		ln -s "${EPREFIX}"/usr/bin/${ELUA} "${workdir}"/bin/lua || die
+		ln -s "${EPREFIX}"/usr/bin/${ELUA/a/ac} "${workdir}"/bin/luac || die
+
+		# pkg-config
+		ln -s "${EPREFIX}"/usr/$(get_libdir)/pkgconfig/${ELUA}.pc \
+			"${workdir}"/pkgconfig/lua.pc || die
+	fi
+
+	# Now, set the environment.
+	# But note that ${workdir} may be shared with something else,
+	# and thus already on top of PATH.
+	if [[ ${PATH##:*} != ${workdir}/bin ]]; then
+		PATH=${workdir}/bin${PATH:+:${PATH}}
+	fi
+	if [[ ${PKG_CONFIG_PATH##:*} != ${workdir}/pkgconfig ]]; then
+		PKG_CONFIG_PATH=${workdir}/pkgconfig${PKG_CONFIG_PATH:+:${PKG_CONFIG_PATH}}
+	fi
+	export PATH PKG_CONFIG_PATH
+}
+
+# @FUNCTION: lua_copy_sources
+# @DESCRIPTION:
+# Create a single copy of the package sources for each enabled Lua
+# implementation.
+#
+# The sources are always copied from initial BUILD_DIR (or S if unset)
+# to implementation-specific build directory matching BUILD_DIR used by
+# lua_foreach_abi().
+lua_copy_sources() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local MULTIBUILD_VARIANTS
+	_lua_obtain_impls
+
+	multibuild_copy_sources
+}
+
+# @FUNCTION: lua_foreach_impl
+# @USAGE: <command> [<args>...]
+# @DESCRIPTION:
+# Run the given command for each of the enabled Lua implementations.
+# If additional parameters are passed, they will be passed through
+# to the command.
+#
+# The function will return 0 status if all invocations succeed.
+# Otherwise, the return code from first failing invocation will
+# be returned.
+#
+# For each command being run, ELUA, LUA and BUILD_DIR are set
+# locally, and the former two are exported to the command environment.
+lua_foreach_impl() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local MULTIBUILD_VARIANTS
+	_lua_obtain_impls
+
+	multibuild_foreach_variant _lua_multibuild_wrapper "${@}"
+}
+
+# @FUNCTION: lua_get_CFLAGS
+# @USAGE: [<impl>]
+# @DESCRIPTION:
+# Obtain and print the compiler flags for building against Lua,
+# for the given implementation. If no implementation is provided,
+# ${ELUA} will be used.
+#
+# Please note that this function requires Lua and pkg-config installed,
+# and therefore proper build-time dependencies need be added to the ebuild.
+lua_get_CFLAGS() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	_lua_export "${@}" LUA_CFLAGS
+	echo "${LUA_CFLAGS}"
+}
+
+# @FUNCTION: lua_get_cmod_dir
+# @USAGE: [<impl>]
+# @DESCRIPTION:
+# Obtain and print the name of the directory into which compiled Lua
+# modules are installed, for the given implementation. If no implementation
+# is provided, ${ELUA} will be used.
+#
+# Please note that this function requires Lua and pkg-config installed,
+# and therefore proper build-time dependencies need be added to the ebuild.
+lua_get_cmod_dir() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	_lua_export "${@}" LUA_CMOD_DIR
+	echo "${LUA_CMOD_DIR}"
+}
+
+# @FUNCTION: lua_get_LIBS
+# @USAGE: [<impl>]
+# @DESCRIPTION:
+# Obtain and print the compiler flags for linking against Lua,
+# for the given implementation. If no implementation is provided,
+# ${ELUA} will be used.
+#
+# Please note that this function requires Lua and pkg-config installed,
+# and therefore proper build-time dependencies need be added to the ebuild.
+lua_get_LIBS() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	_lua_export "${@}" LUA_LIBS
+	echo "${LUA_LIBS}"
+}
+
+# @FUNCTION: lua_get_lmod_dir
+# @USAGE: [<impl>]
+# @DESCRIPTION:
+# Obtain and print the name of the directory into which native-Lua
+# modules are installed, for the given implementation. If no implementation
+# is provided, ${ELUA} will be used.
+#
+# Please note that this function requires Lua and pkg-config installed,
+# and therefore proper build-time dependencies need be added to the ebuild.
+lua_get_lmod_dir() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	_lua_export "${@}" LUA_LMOD_DIR
+	echo "${LUA_LMOD_DIR}"
+}
+
+# @FUNCTION: lua_get_version
+# @USAGE: [<impl>]
+# @DESCRIPTION:
+# Obtain and print the full version number of the given Lua implementation.
+# If no implementation is provided, ${ELUA} will be used.
+#
+# Please note that this function requires Lua and pkg-config installed,
+# and therefore proper build-time dependencies need be added to the ebuild.
+lua_get_version() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	_lua_export "${@}" LUA_VERSION
+	echo "${LUA_VERSION}"
+}
+
+_LUA_R0=1
+fi
+
+# @ECLASS-VARIABLE: _LUA_ALL_IMPLS
+# @INTERNAL
+# @DESCRIPTION:
+# All supported Lua implementations, most preferred last
+_LUA_ALL_IMPLS=(
+	lua5-1
+	lua5-2
+	lua5-3
+	lua5-4
+)
+readonly _LUA_ALL_IMPLS
+
+# @FUNCTION: _lua_set_impls
+# @INTERNAL
+# @DESCRIPTION:
+# Check LUA_COMPAT for well-formedness and validity, then set
+# two global variables:
+#
+# - _LUA_SUPPORTED_IMPLS containing valid implementations supported
+#   by the ebuild (LUA_COMPAT - dead implementations),
+#
+# - and _LUA_UNSUPPORTED_IMPLS containing valid implementations that
+#   are not supported by the ebuild.
+#
+# Implementations in both variables are ordered using the pre-defined
+# eclass implementation ordering.
+#
+# This function must only be called once.
+_lua_set_impls() {
+	local i
+
+	if ! declare -p LUA_COMPAT &>/dev/null; then
+		die 'LUA_COMPAT not declared.'
+	fi
+	if [[ $(declare -p LUA_COMPAT) != "declare -a"* ]]; then
+		die 'LUA_COMPAT must be an array.'
+	fi
+
+	local supp=() unsupp=()
+
+	for i in "${_LUA_ALL_IMPLS[@]}"; do
+		if has "${i}" "${LUA_COMPAT[@]}"; then
+			supp+=( "${i}" )
+		else
+			unsupp+=( "${i}" )
+		fi
+	done
+
+	if [[ ! ${supp[@]} ]]; then
+		die "No supported implementation in LUA_COMPAT."
+	fi
+
+	if [[ ${_LUA_SUPPORTED_IMPLS[@]} ]]; then
+		# set once already, verify integrity
+		if [[ ${_LUA_SUPPORTED_IMPLS[@]} != ${supp[@]} ]]; then
+			eerror "Supported impls (LUA_COMPAT) changed between inherits!"
+			eerror "Before: ${_LUA_SUPPORTED_IMPLS[*]}"
+			eerror "Now   : ${supp[*]}"
+			die "_LUA_SUPPORTED_IMPLS integrity check failed"
+		fi
+		if [[ ${_LUA_UNSUPPORTED_IMPLS[@]} != ${unsupp[@]} ]]; then
+			eerror "Unsupported impls changed between inherits!"
+			eerror "Before: ${_LUA_UNSUPPORTED_IMPLS[*]}"
+			eerror "Now   : ${unsupp[*]}"
+			die "_LUA_UNSUPPORTED_IMPLS integrity check failed"
+		fi
+	else
+		_LUA_SUPPORTED_IMPLS=( "${supp[@]}" )
+		_LUA_UNSUPPORTED_IMPLS=( "${unsupp[@]}" )
+		readonly _LUA_SUPPORTED_IMPLS _LUA_UNSUPPORTED_IMPLS
+	fi
+}
+
+# @FUNCTION: _lua_set_globals
+# @INTERNAL
+# @DESCRIPTION:
+# Sets all the global output variables provided by this eclass.
+# This function must be called once, in global scope.
+_lua_set_globals() {
+	local deps i LUA_PKG_DEP
+
+	_lua_set_impls
+
+	for i in "${_LUA_SUPPORTED_IMPLS[@]}"; do
+		_lua_export "${i}" LUA_PKG_DEP
+		deps+="lua_targets_${i}? ( ${LUA_PKG_DEP} ) "
+	done
+
+	local flags=( "${_LUA_SUPPORTED_IMPLS[@]/#/lua_targets_}" )
+	local optflags=${flags[@]/%/(-)?}
+
+	local requse="|| ( ${flags[*]} )"
+	local usedep=${optflags// /,}
+
+	if [[ ${LUA_DEPS+1} ]]; then
+		# IUSE is magical, so we can't really check it
+		# (but we verify LUA_COMPAT already)
+
+		if [[ ${LUA_DEPS} != "${deps}" ]]; then
+			eerror "LUA_DEPS have changed between inherits (LUA_REQ_USE?)!"
+			eerror "Before: ${LUA_DEPS}"
+			eerror "Now   : ${deps}"
+			die "LUA_DEPS integrity check failed"
+		fi
+
+		# these two are formality -- they depend on LUA_COMPAT only
+		if [[ ${LUA_REQUIRED_USE} != ${requse} ]]; then
+			eerror "LUA_REQUIRED_USE have changed between inherits!"
+			eerror "Before: ${LUA_REQUIRED_USE}"
+			eerror "Now   : ${requse}"
+			die "LUA_REQUIRED_USE integrity check failed"
+		fi
+
+		if [[ ${LUA_USEDEP} != "${usedep}" ]]; then
+			eerror "LUA_USEDEP have changed between inherits!"
+			eerror "Before: ${LUA_USEDEP}"
+			eerror "Now   : ${usedep}"
+			die "LUA_USEDEP integrity check failed"
+		fi
+	else
+		IUSE=${flags[*]}
+
+		LUA_DEPS=${deps}
+		LUA_REQUIRED_USE=${requse}
+		LUA_USEDEP=${usedep}
+		readonly LUA_DEPS LUA_REQUIRED_USE
+	fi
+}
+
+_lua_set_globals
+unset -f _lua_set_globals _lua_set_impls
-- 
2.26.2