[gentoo-dev] [PATCH] multibuild.eclass: supporting introspecting all layers of nested multibuild

[Michał Górny]

Transform MULTIBUILD_VARIANT, MULTIBUILD_ID and BUILD_DIR into arrays
preserving values for each nested multibuild layer. For example, if you
do something like:

  MULTIBUILD_VARIANTS=( a b c )
  multibuild_foreach_variant multilib_foreach_abi python_foreach_impl ..

then the function called last would have:

  MULTIBUILD_VARIANT=( python2.7 abi_x86_64.amd64 a )
  MULTIBUILD_ID=( a-abi_x86_64.amd64-python2.7 a-abi_x86_64.amd64 a )

and BUILD_DIR alike it. Which means that using ${MULTIBUILD_VARIANT[2]}
you can get your initial 'a' without having to copy intermediate values.

Of course, if you want to nest multibuild you still need to ensure to
set proper MULTIBUILD_VARIANTS in the scope of multibuild_foreach*
invocation.

And before you start to worry, this is fully backwards-compatible.
In bash, ${MULTIBUILD_VARIANT} is equivalent to ${MULTIBUILD_VARIANT[0]}
in context of an array, and since index 0 stores deepmost value ---
nothing changes :).

Fixes: https://bugs.gentoo.org/show_bug.cgi?id=483758
---
 eclass/multibuild.eclass | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/eclass/multibuild.eclass b/eclass/multibuild.eclass
index de5804d..c8a9591 100644
--- a/eclass/multibuild.eclass
+++ b/eclass/multibuild.eclass
@@ -48,6 +48,10 @@ inherit multiprocessing
 # @DESCRIPTION:
 # The current variant which the function was executed for.
 #
+# If nested multibuilds are used, this value can be an array. In that
+# case, the first element will name the deepest multibuild, and the next
+# elements will go outwards.
+#
 # Example value:
 # @CODE
 # python2_6
@@ -61,6 +65,10 @@ inherit multiprocessing
 #
 # It can be used to create variant-unique directories and files.
 #
+# If nested multibuilds are used, this value can be an array. In that
+# case, the first element will name the deepest multibuild, and the next
+# elements will go outwards.
+#
 # Example value:
 # @CODE
 # amd64-double
@@ -75,6 +83,10 @@ inherit multiprocessing
 # to variant-specific build directories based on the initial value
 # of BUILD_DIR.
 #
+# If nested multibuilds are used, this value can be an array. In that
+# case, the first element will name the deepest multibuild, and the next
+# elements will go outwards.
+#
 # Example value:
 # @CODE
 # ${WORKDIR}/foo-1.3-python2_6
@@ -110,9 +122,9 @@ multibuild_foreach_variant() {
 	debug-print "${FUNCNAME}: initial build_dir = ${bdir}"
 
 	for v in "${MULTIBUILD_VARIANTS[@]}"; do
-		local MULTIBUILD_VARIANT=${v}
-		local MULTIBUILD_ID=${prev_id}${v}
-		local BUILD_DIR=${bdir%%/}-${v}
+		local MULTIBUILD_VARIANT=( "${v}" "${MULTIBUILD_VARIANT[@]}" )
+		local MULTIBUILD_ID=( "${prev_id}${v}" "${MULTIBUILD_ID[@]}" )
+		local BUILD_DIR=( "${bdir%%/}-${v}" "${BUILD_DIR[@]}" )
 
 		_multibuild_run() {
 			# find the first non-private command
-- 
2.1.0