[gentoo-dev] [PATCH 1/7] multibuild: introduce a generic framework for custom phase functions.

["Michał Górny" <mgorny@gentoo.org>]

The framework provides functions to declare, export and obtain custom
phase functions.

Each of the custom phases can be defined by eclasses and ebuilds
in a manner similar to regular phases. The eclasses define
${ECLASS}_${phase} function and run 'multibuild_export_phases' to
register them. The ebuilds define ${phase} function and it automatically
takes precedence over eclass-defined ones.
---
 gx86/eclass/multibuild.eclass | 61 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/gx86/eclass/multibuild.eclass b/gx86/eclass/multibuild.eclass
index bc510e9..ea0500c 100644
--- a/gx86/eclass/multibuild.eclass
+++ b/gx86/eclass/multibuild.eclass
@@ -28,6 +28,8 @@ if [[ ! ${_MULTIBUILD} ]]; then
 
 inherit multiprocessing
 
+DEPEND=">=app-shells/bash-4.2"
+
 # @ECLASS-VARIABLE: MULTIBUILD_VARIANTS
 # @DESCRIPTION:
 # An array specifying all enabled variants which multibuild_foreach*
@@ -245,5 +247,64 @@ run_in_build_dir() {
 	return ${ret}
 }
 
+# @FUNCTION: multibuild_export_phases
+# @USAGE: <phase-name>...
+# @DESCRIPTION:
+# Export the eclass phase functions for named phases. The functions need
+# be named ${ECLASS}_<phase-name>. The exported functions will override
+# any previously exported phases.
+multibuild_export_phases() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -eq 0 ]] && die "Usage: multibuild_export_phases <phase-name>..."
+
+	# This is necessary to allow sourcing of the ebuild with old bash
+	# versions, e.g. for cachegen.
+	if [[ $(( (BASH_VERSINFO[0] << 8) + BASH_VERSINFO[1] )) \
+			-lt $(( (4 << 8) + 2 )) ]] ; then
+		_MULTIBUILD_ANCIENT_BASH=1
+		return 0
+	fi
+
+	declare -g -A _MULTIBUILD_EXPORTED_PHASES || die
+	local p
+	for p; do
+		_MULTIBUILD_EXPORTED_PHASES[${p}]=${ECLASS}_${p}
+	done
+}
+
+# @FUNCTION: multibuild_get_phase_function
+# @USAGE: <phase-name>
+# @DESCRIPTION:
+# Find the topmost handler for the named phase. It can be either
+# user-defined phase handler (with the same name as the phase)
+# or a handler exported most recently by an eclass.
+#
+# Prints the function name to stdout or null string if there is
+# no handler for the phase.
+multibuild_get_phase_function() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	[[ ${#} -ne 1 ]] && die "Usage: multibuild_get_phase_function <phase-name>"
+	if [[ ${_MULTIBUILD_ANCIENT_BASH} ]]; then
+		die "Old bash (<4.2) used to start the build, please restart emerge."
+	fi
+
+	local phase=${1}
+
+	# user-defined phase
+	if ! declare -f "${phase}" >/dev/null; then
+		phase=${_MULTIBUILD_EXPORTED_PHASES[${phase}]}
+
+		if [[ ! ${phase} ]]; then
+			return
+		elif ! declare -f "${phase}" >/dev/null; then
+			die "Phase function ${phase} exported but never defined!"
+		fi
+	fi
+
+	echo "${phase}"
+}
+
 _MULTIBUILD=1
 fi
-- 
1.8.1.5