eclass/opam.eclass: Changes from ml-overlay

Co-Author: Alexis Ballier <aballier@gentoo.org>
Signed-off-by: Mark Wright <gienah@gentoo.org>

eclass/opam.eclass

@@ -1,9 +1,9 @@
-# Copyright 1999-2019 Gentoo Authors
+# Copyright 1999-2020 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: opam.eclass
 # @MAINTAINER:
-# maintainer-needed@gentoo.org
+# Mark Wright <gienah@gentoo.org>
 # @AUTHOR:
 # Alexis Ballier <aballier@gentoo.org>
 # @SUPPORTED_EAPIS: 5 6 7
@@ -17,9 +17,21 @@ case ${EAPI:-0} in
 	*) die "${ECLASS}: EAPI ${EAPI} not supported" ;;
 esac
 
+# @ECLASS-VARIABLE: OPAM_INSTALLER_DEP
+# @DESCRIPTION:
+# Override dependency for OPAM_INSTALLER
+: ${OPAM_INSTALLER_DEP:="dev-ml/opam-installer"}
+
 RDEPEND=">=dev-lang/ocaml-4:="
-DEPEND="${RDEPEND}
-	dev-ml/opam"
+case ${EAPI:-0} in
+	0|1|2|3|4|5|6) DEPEND="${RDEPEND} ${OPAM_INSTALLER_DEP}";;
+	*) BDEPEND="${OPAM_INSTALLER_DEP} dev-lang/ocaml"; DEPEND="${RDEPEND}" ;;
+esac
+
+# @ECLASS-VARIABLE: OPAM_INSTALLER
+# @DESCRIPTION:
+# Eclass can use different opam-installer binary than the one provided in by system.
+: ${OPAM_INSTALLER:=opam-installer}
 
 # @FUNCTION: opam-install
 # @USAGE: <list of packages>
@@ -29,7 +41,7 @@ DEPEND="${RDEPEND}
 opam-install() {
 	local pkg
 	for pkg ; do
-		opam-installer -i \
+		${OPAM_INSTALLER} -i \
 			--prefix="${ED%/}/usr" \
 			--libdir="${D%/}/$(ocamlc -where)" \
 			--docdir="${ED%/}/usr/share/doc/${PF}" \