[gentoo-dev] [PATCH] eutils.eclass: add optfeature() function

[Chris Reffett <creffett@gentoo.org>]

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Hello all,
After some discussion on good ways to communicate optional
dependencies to users, I was shown the optfeature() function in
net-misc/netctl. Gentoo contributor Andrew Hamilton and I came up with
a cleaned up and expanded version of it, and I would like to add it to
eutils.eclass to provide a standard way of notifying users of optional
dependencies. The patch to eutils.eclass is attached.

Chris Reffett
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--- eutils.eclass	2014-01-22 23:36:35.819000000 -0500
+++ eutils.eclass.patched	2014-01-23 00:37:07.907000000 -0500
@@ -1729,4 +1729,49 @@
 
 check_license() { die "you no longer need this as portage supports ACCEPT_LICENSE itself"; }
 
+# @FUNCTION: optfeature
+# @USAGE: <short description> <package atom to match> [other atoms]
+# @DESCRIPTION:
+# Print out a message suggesting an optional package (or packages) which
+# provide the described functionality
+#
+# The following snippet would suggest app-misc/foo for optional foo support,
+# app-misc/bar or app-misc/baz[bar] for optional bar support
+# and either both app-misc/a and app-misc/b or app-misc/c for alphabet support.
+# @CODE:
+# 		optfeature "foo support" app-misc/foo
+# 		optfeature "bar support" app-misc/bar app-misc/baz[bar]
+#		optfeature "alphabet support" "app-misc/a app-misc/b" app-misc/c
+#
+optfeature() {
+	debug-print-function ${FUNCNAME} "$@"
+	local i j msg
+	local desc=$1
+	local flag=0
+	shift
+	for i; do
+		for j in $i; do
+			if has_version "$j"; then
+				flag=1
+			else
+				flag=0
+				break
+			fi
+		done
+		if [[ $flag -eq 1 ]]; then
+			break
+		fi
+	done
+	if [[ $flag -eq 0 ]]; then
+		for i; do
+			msg=" "
+			for j in $i; do
+				msg="${msg} ${j} and"
+			done
+			msg="${msg:0: -4} for ${desc}"
+			elog "${msg}"
+		done
+	fi
+}
+
 fi