luci-base: support option aliases in luci.cbi

AbstractValue descendants may now specify a new optional property `alias`
which refers to a uci option to read/write/remove that differs from the
option name itself.

This is mainly useful for widgets that are toggled based on dependencies,
e.g. for alternating between SingleValue and MultiValue, but which are
intented to write into the same uci option.

Such a setup was previously possible already by overriding the .cfgvalue(),
.write() and .remove() callbacks with custom implementations, but that
required a lot of boiler plate code and was rather fragile.

With the `alias` property, CBI now takes care of the details and tracks
aliased fields within a section accordingly.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 19 insertions, 7 deletions

diff --git a/modules/luci-base/luasrc/cbi.lua b/modules/luci-base/luasrc/cbi.lua
index 4800d2aa72..3a55eb23c8 100644
--- a/modules/luci-base/luasrc/cbi.lua
+++ b/modules/luci-base/luasrc/cbi.lua
@@ -1417,6 +1417,12 @@ function AbstractValue.parse(self, section, novld)
 			self:add_error(section, "invalid", val_err)
 		end
 
+		if self.alias then
+			self.section.aliased = self.section.aliased or {}
+			self.section.aliased[section] = self.section.aliased[section] or {}
+			self.section.aliased[section][self.alias] = true
+		end
+
 		if fvalue and (self.forcewrite or not (fvalue == cvalue)) then
 			if self:write(section, fvalue) then
 				-- Push events
@@ -1426,10 +1432,16 @@ function AbstractValue.parse(self, section, novld)
 		end
 	else							-- Unset the UCI or error
 		if self.rmempty or self.optional then
-			if self:remove(section) then
-				-- Push events
-				self.section.changed = true
-				--luci.util.append(self.map.events, self.events)
+			if not self.alias or
+			   not self.section.aliased or
+			   not self.section.aliased[section] or
+			   not self.section.aliased[section][self.alias]
+			then
+				if self:remove(section) then
+					-- Push events
+					self.section.changed = true
+					--luci.util.append(self.map.events, self.events)
+				end
 			end
 		elseif cvalue ~= fvalue and not novld then
 			-- trigger validator with nil value to get custom user error msg.
@@ -1455,7 +1467,7 @@ function AbstractValue.cfgvalue(self, section)
 	if self.tag_error[section] then
 		value = self:formvalue(section)
 	else
-		value = self.map:get(section, self.option)
+		value = self.map:get(section, self.alias or self.option)
 	end
 
 	if not value then
@@ -1496,12 +1508,12 @@ AbstractValue.transform = AbstractValue.validate
 
 -- Write to UCI
 function AbstractValue.write(self, section, value)
-	return self.map:set(section, self.option, value)
+	return self.map:set(section, self.alias or self.option, value)
 end
 
 -- Remove from UCI
 function AbstractValue.remove(self, section)
-	return self.map:del(section, self.option)
+	return self.map:del(section, self.alias or self.option)
 end