[gentoo-dev] [PATCH] rebar.eclass: Build Erlang/OTP projects using dev-util/rebar

From: Amadeusz Żołnowski <aidecoe@g.o>

It is an eclass providing functions to build Erlang/OTP projects using
dev-util/rebar. All packages in upcoming category dev-erlang are going
to use this eclass.
---
 eclass/rebar.eclass | 223 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 223 insertions(+)
 create mode 100644 eclass/rebar.eclass

diff --git a/eclass/rebar.eclass b/eclass/rebar.eclass
new file mode 100644
index 0000000..1a4eaba
--- /dev/null
+++ b/eclass/rebar.eclass
@@ -0,0 +1,223 @@
+# Copyright 1999-2016 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+# $Id$
+
+# @ECLASS: rebar.eclass
+# @MAINTAINER:
+# Amadeusz Żołnowski <aidecoe@g.o>
+# @AUTHOR:
+# Amadeusz Żołnowski <aidecoe@g.o>
+# @BLURB: Build Erlang/OTP projects using dev-util/rebar.
+# @DESCRIPTION:
+# An eclass providing functions to build Erlang/OTP projects using
+# dev-util/rebar.
+#
+# rebar is a tool which tries to resolve dependencies itself which is by
+# cloning remote git repositories. Dependant projects are usually expected to
+# be in sub-directory 'deps' rather than looking at system Erlang lib
+# directory. Projects relying on rebar usually don't have 'install' make
+# targets. The eclass workarounds some of these problems. It handles
+# installation in a generic way for Erlang/OTP structured projects.
+
+case "${EAPI:-0}" in
+	0|1|2|3|4|5)
+		die "Unsupported EAPI=${EAPI:-0} (too old) for ${ECLASS}"
+		;;
+	6)
+		;;
+	*)
+		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
+		;;
+esac
+
+EXPORT_FUNCTIONS src_prepare src_compile src_install
+
+RDEPEND="dev-lang/erlang"
+DEPEND="${RDEPEND}
+	dev-util/rebar
+	>=sys-apps/gawk-4.1"
+
+# @ECLASS-VARIABLE: REBAR_APP_SRC
+# @DESCRIPTION:
+# Relative path to .app.src description file.
+REBAR_APP_SRC="${REBAR_APP_SRC-src/${PN}.app.src}"
+
+# @FUNCTION: get_erl_libs
+# @RETURN: the path to Erlang lib directory
+# @DESCRIPTION:
+# Get the full path without EPREFIX to Erlang lib directory.
+get_erl_libs() {
+	echo "/usr/$(get_libdir)/erlang/lib"
+}
+
+# @FUNCTION: _rebar_find_dep
+# @INTERNAL
+# @USAGE: <project_name>
+# @RETURN: full path with EPREFIX to a Erlang package/project on success,
+# code 1 when dependency is not found and code 2 if multiple versions of
+# dependency are found.
+# @DESCRIPTION:
+# Find a Erlang package/project by name in Erlang lib directory. Project
+# directory is usually suffixed with version. It is matched to '<project_name>'
+# or '<project_name>-*'.
+_rebar_find_dep() {
+	local pn="$1"
+	local p
+	local result
+
+	pushd "${EPREFIX}$(get_erl_libs)" >/dev/null || return 1
+	for p in ${pn} ${pn}-*; do
+		if [[ -d ${p} ]]; then
+			# Ensure there's at most one matching.
+			[[ ${result} ]] && return 2
+			result="${p}"
+		fi
+	done
+	popd >/dev/null || die
+
+	[[ ${result} ]] || return 1
+	echo "${result}"
+}
+
+# @FUNCTION: erebar
+# @USAGE: <targets>
+# @DESCRIPTION:
+# Run rebar with verbose flag. Die on failure.
+erebar() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	(( $# > 0 )) || die "erebar: at least one target is required"
+
+	local -x ERL_LIBS="${EPREFIX}$(get_erl_libs)"
+	rebar -v skip_deps=true "$@" || die "rebar $@ failed"
+}
+
+# @FUNCTION: rebar_fix_include_path
+# @USAGE: <project_name>
+# @DESCRIPTION:
+# Fix path in rebar.config to 'include' directory of dependant project/package,
+# so it points to installation in system Erlang lib rather than relative 'deps'
+# directory.
+#
+# The function dies on failure.
+rebar_fix_include_path() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local pn="$1"
+	local erl_libs="${EPREFIX}$(get_erl_libs)"
+	local p
+
+	p="$(_rebar_find_dep "${pn}")" \
+		|| die "failed to unambiguously resolve dependency of '${pn}'"
+
+	gawk -i inplace \
+		-v erl_libs="${erl_libs}" -v pn="${pn}" -v p="${p}" '
+/^{[[:space:]]*erl_opts[[:space:]]*,/, /}[[:space:]]*\.$/ {
+	pattern = "\"(./)?deps/" pn "/include\"";
+	if (match($0, "{i,[[:space:]]*" pattern "[[:space:]]*}")) {
+		sub(pattern, "\"" erl_libs "/" p "/include\"");
+	}
+	print $0;
+	next;
+}
+1
+' rebar.config || die "failed to fix include paths in rebar.config for '${pn}'"
+}
+
+# @FUNCTION: rebar_remove_deps
+# @DESCRIPTION:
+# Remove dependencies list from rebar.config and deceive build rules that any
+# dependencies are already fetched and built. Otherwise rebar tries to fetch
+# dependencies and compile them.
+#
+# The function dies on failure.
+rebar_remove_deps() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	mkdir -p "${S}/deps" && :>"${S}/deps/.got" && :>"${S}/deps/.built" || die
+	gawk -i inplace '
+/^{[[:space:]]*deps[[:space:]]*,/, /}[[:space:]]*\.$/ {
+	if ($0 ~ /}[[:space:]]*\.$/) {
+		print "{deps, []}.";
+	}
+	next;
+}
+1
+' rebar.config || die "failed to remove deps from rebar.config"
+}
+
+# @FUNCTION: rebar_set_vsn
+# @USAGE: [<version>]
+# @DESCRIPTION:
+# Set version in project description file if it's not set.
+#
+# <version> is optional. Default is PV stripped from version suffix.
+#
+# The function dies on failure.
+rebar_set_vsn() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local version="${1:-${PV%_*}}"
+
+	sed -e "s/vsn, git/vsn, \"${version}\"/" \
+		-i "${S}/${REBAR_APP_SRC}" \
+		|| die "failed to set version in src/${PN}.app.src"
+}
+
+# @FUNCTION: rebar_src_prepare
+# @DESCRIPTION:
+# Prevent rebar from fetching in compiling dependencies. Set version in project
+# description file if it's not set.
+#
+# Existence of rebar.config is optional, but file description file must exist
+# at 'src/${PN}.app.src'.
+rebar_src_prepare() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	default
+	rebar_set_vsn
+	[[ -f rebar.config ]] && rebar_remove_deps
+}
+
+# @FUNCTION: rebar_src_configure
+# @DESCRIPTION:
+# Configure with ERL_LIBS set.
+rebar_src_configure() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local -x ERL_LIBS="${EPREFIX}$(get_erl_libs)"
+	default
+}
+
+# @FUNCTION: rebar_src_compile
+# @DESCRIPTION:
+# Compile project with rebar.
+rebar_src_compile() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	erebar compile
+}
+
+# @FUNCTION: rebar_src_install
+# @DESCRIPTION:
+# Install BEAM files, include headers, executables and native libraries.
+# Install standard docs like README or defined in DOCS variable.
+#
+# Function expects that project conforms to Erlang/OTP structure.
+rebar_src_install() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local bin
+	local dest="$(get_erl_libs)/${P}"
+
+	insinto "${dest}"
+	doins -r ebin
+	[[ -d include ]] && doins -r include
+	[[ -d bin ]] && for bin in bin/*; do dobin "$bin"; done
+
+	if [[ -d priv ]]; then
+		cp -pR priv "${ED}${dest}/" || die "failed to install priv/"
+	fi
+
+	einstalldocs
+}
-- 
2.8.2