Switch back to tag:pop instead of tag:trim

The tag operator should allow for all the user-defined tagging you need, and it already ensures the stack stays consistent so there's no need to be extra careful with tag:trim.

interpreter/common.lua

@@ -191,12 +191,10 @@ common = {
 			for k, v in pairs(common.to_lua(val)) do new[k] = v end
 			-- add
 			table.insert(state.interpreter.tags, new)
-			return self:len(state)
 		end,
 		--- same but do not merge with last stack item
 		push_lua_no_merge = function(self, state, val)
 			table.insert(state.interpreter.tags, val)
-			return self:len(state)
 		end,
 		-- pop tag table on top of the stack
 		pop = function(self, state)
@@ -211,8 +209,7 @@ common = {
 			return #state.interpreter.tags
 		end,
 		--- pop item until we reached desired stack length
-		-- try to prefer this to pop if possible, so in case we mess up the stack somehow it will restore the stack to a good state
+		-- so in case there's a possibility to mess up the stack somehow, it will restore the stack to a good state
-		-- (we may allow tag push/pop from the user side at some point TODO)
 		trim = function(self, state, len)
 			while #state.interpreter.tags > len do
 				self:pop(state)
@@ -342,9 +339,9 @@ common = {
 						-- execute in expected tag & event capture state
 						local capture_state = state.interpreter.event_capture_stack
 						state.interpreter.event_capture_stack = {}
-						local i = common.tags:push_lua_no_merge(state, choice.tags)
+						common.tags:push_lua_no_merge(state, choice.tags)
 						local _, e = run_block(state, choice.block)
-						common.tags:trim(state, i-1)
+						common.tags:pop(state)
 						state.interpreter.event_capture_stack = capture_state
 						if e then return nil, e end
 						-- we discard return value from choice block as the execution is delayed until an event flush

interpreter/expression.lua

@@ -138,9 +138,9 @@ local function eval(state, exp)
 	elseif exp.type == "#" then
 		local right, righte = eval(state, exp.right)
 		if not right then return right, righte end
-		local i = tags:push(state, right)
+		tags:push(state, right)
 		local left, lefte = eval(state, exp.left)
-		tags:trim(state, i-1)
+		tags:pop(state)
 		if not left then return left, lefte end
 		return left
 	-- variable

interpreter/interpreter.lua

@@ -47,9 +47,9 @@ run_line = function(state, line)
 	elseif line.type == "tag" then
 		local v, e = eval(state, line.expression)
 		if not v then return v, ("%s; at %s"):format(e, line.source) end
-		local i = tags:push(state, v)
+		tags:push(state, v)
 		v, e = run_block(state, line.child)
-		tags:trim(state, i-1)
+		tags:pop(state)
 		if e then return v, e end
 		if v then return v end
 	elseif line.type == "return" then
@@ -180,7 +180,7 @@ local function run(state, block, resume_from_there, i, j)
 	local v, e = run_block(state, block, resume_from_there, i, j)
 	-- return to previous tag state
 	-- when resuming is done, tag stack pop when exiting the tag block
-	-- stray elements may be left on the stack if there is a return before we exit all the tag block, so we trim them
+	-- stray elements may be left on the stack if there is a return before we go up all the tag blocks, so we trim them
 	if resume_from_there then
 		tags:trim(state, tags_len)
 	end