texmod: Stricter file name validation

minetest/texmod/dsl.lua

@@ -11,6 +11,8 @@ setmetatable(texmod, {__call = new})
 -- Constructors / "generators"
 
 function texmod.file(filename)
+	-- See `TEXTURENAME_ALLOWED_CHARS` in Minetest (`src/network/networkprotocol.h`)
+	assert(not filename:find"[^%w_.-]", "invalid characters in file name")
 	return new{
 		type = "file",
 		filename = filename

minetest/texmod/read.lua

@@ -251,6 +251,9 @@ function rm.fname(r)
 	-- This is overly permissive, as is Minetest;
 	-- we just allow arbitrary characters up until a character which may terminate the name.
 	-- Inside an inventorycube, `&` also terminates names.
+	-- Note that the constructor will however - unlike Minetest - perform validation.
+	-- We could leverage the knowledge of the allowed charset here already,
+	-- but that might lead to more confusing error messages.
 	return r:match_str(r.invcube and "[^:^&){]" or "[^:^){]")
 end
 function rm.subtexp(r)

minetest/texmod/write.lua

@@ -123,7 +123,6 @@ return function(self, write_str)
 	end
 	function w.tex(tex)
 		if tex.type == "file" then
-			assert(not tex.filename:find"[:^\\&{[]", "invalid character in filename")
 			w.str(tex.filename)
 			return
 		end