skinlist: avoid 'Too many open files' errors

Due to application-specific file descriptor limits,
the garbage collector cannot close the descriptors in time,
resulting in unexpected file open errors.

API.md

@@ -27,6 +27,31 @@ Get all allowed skins for player. All public and all player's private skins. If
 Get all skins with metadata key is set to value. Example:
 skins.get_skinlist_with_meta("playername", playername) - Get all private skins (w.o. public) for playername
 
+## skins.register_skin(path, filename)
+Registers a new skin based on the texture file path specified by `path` and `filename`.
+
+ * `path` (string): points to the parent directory of the texture `filename`.
+   Generally, this should be in the format `mymod.modpath .. "/textures"`.
+ * `filename` (string): full file name, without any path specifications.
+   The file name must adhere to [one of the accepted naming formats](textures/readme.txt).
+
+Note: this function takes the following files into consideration:
+
+1. `<path>/<filename>` (required)
+    * Main skin texture
+2. `<path>/<filenamestem><separator>preview.png` (optional)
+    * Pre-generated preview image
+3. `<path>/../meta/<filenamestem>.txt` (optional)
+    * Metadata regarding the skin
+
+Return values:
+
+ * On failure: `false, reason`
+    * `reason` (string): human readable reason string (similar to `io.open` errors)
+ * On success: `true, key`
+    * `key`: unique skins key for use with e.g. `skins.get(key)` for subsequent
+      fine-tuning of the skin registration.
+
 
 ## skins.new(key, object)
 Create and register a new skin object for given key

api.lua

@@ -2,14 +2,26 @@
 local storage = minetest.get_mod_storage()
 
 function skins.get_player_skin(player)
+	local player_name = player:get_player_name()
 	local meta = player:get_meta()
 	if meta:get("skinsdb:skin_key") then
 		-- Move player data prior July 2018 to mod storage
-		storage:set_string(player:get_player_name(), meta:get_string("skinsdb:skin_key"))
+		storage:set_string(player_name, meta:get_string("skinsdb:skin_key"))
 		meta:set_string("skinsdb:skin_key", "")
 	end
-	local skin = storage:get_string(player:get_player_name())
+
-	return skins.get(skin) or skins.get(skins.default)
+	local skin_name = storage:get_string(player_name)
+	local skin = skins.get(skin_name)
+	if #skin_name > 0 and not skin then
+		-- Migration step to convert `_`-delimited skins to `.` (if possible)
+		skin = skins.__fuzzy_match_skin_name(player_name, skin_name, true)
+		if skin then
+			storage:set_string(player_name, skin:get_key())
+		else
+			storage:set_string(player_name, "")
+		end
+	end
+	return skin or skins.get(skins.default)
 end
 
 -- Assign skin to player

init.lua

@@ -111,3 +111,6 @@ minetest.register_allow_player_inventory_action(function(player, action, inv, da
 		return 0
 	end
 end)
+
+--dofile(skins.modpath.."/unittest.lua")
+

skinlist.lua

@@ -2,7 +2,8 @@ local dbgprint = false and print or function() end
 
 --- @param path     Path to the "textures" directory, without tailing slash.
 --- @param filename Current file name, such as "player.groot.17.png".
-local function process_skin_texture(path, filename)
+--- @return On error: false, error message. On success: true, skin key
+function skins.register_skin(path, filename)
 	-- See "textures/readme.txt" for allowed formats
 
 	local prefix, sep, identifier, extension = filename:match("^(%a+)([_.])([%w_.]+)%.(%a+)$")
@@ -16,17 +17,21 @@ local function process_skin_texture(path, filename)
 
 	-- Filter out files that do not match the allowed patterns
 	if not extension or extension:lower() ~= "png" then
-		return -- Not a skin texture
+		return false, "invalid skin name"
 	end
 	if prefix ~= "player" and prefix ~= "character" then
-		return -- Unknown type
+		return false, "unknown type"
 	end
 
 	local preview_suffix = sep .. "preview"
 	if identifier:sub(-#preview_suffix) == preview_suffix then
-		-- skip preview textures
+		-- The preview texture is added by the main skin texture (if exists)
-		-- This is added by the main skin texture (if exists)
+		return false, "preview texture"
-		return
+	end
+
+	assert(path)
+	if path == ":UNITTEST:" then
+		path = nil
 	end
 
 	dbgprint("Found skin", prefix, identifier, extension)
@@ -58,12 +63,16 @@ local function process_skin_texture(path, filename)
 	local skin_obj = skins.get(filename_noext) or skins.new(filename_noext)
 	skin_obj:set_texture(filename)
 	skin_obj:set_meta("_sort_id", sort_id)
+	if sep ~= "_" then
+		skin_obj._legacy_name = filename_noext:gsub("[._]+", "_")
+	end
+
 	if playername then
 		skin_obj:set_meta("assignment", "player:"..playername)
 		skin_obj:set_meta("playername", playername)
 	end
 
-	do
+	if path then
 		-- Get type of skin based on dimensions
 		local file = io.open(path .. "/" .. filename, "r")
 		local skin_format = skins.get_skin_format(file)
@@ -74,7 +83,7 @@ local function process_skin_texture(path, filename)
 	skin_obj:set_hand_from_texture()
 	skin_obj:set_meta("name", identifier)
 
-	do
+	if path then
 		-- Optional skin information
 		local file = io.open(path .. "/../meta/" .. filename_noext .. ".txt", "r")
 		if file then
@@ -83,18 +92,50 @@ local function process_skin_texture(path, filename)
 			skin_obj:set_meta("name", data[1])
 			skin_obj:set_meta("author", data[2])
 			skin_obj:set_meta("license", data[3])
+			file:close() -- do not rely on delayed GC
 		end
 	end
 
-	do
+	if path then
 		-- Optional preview texture
 		local preview_name = filename_noext .. sep .. "preview.png"
 		local fh = io.open(path .. "/" .. preview_name)
 		if fh then
 			dbgprint("Found preview", preview_name)
 			skin_obj:set_preview(preview_name)
+			fh:close() -- do not rely on delayed GC
 		end
 	end
+
+	return true, skin_obj:get_key()
+end
+
+--- Internal function. Fallback/migration code for `.`-delimited skin names that
+--- were equipped between d3c7fa7 and 312780c (master branch).
+--- During this period, `.`-delimited skin names were internally registered with
+--- `_` delimiters. This function tries to find a matching skin.
+--- @param player_name (string)
+--- @param skin_name   (string) e.g. `player_foo_mc_bar`
+--- @param be_noisy    (boolean) whether to print a warning in case of mismatches`
+--- @return On match, the new skin (skins.skin_class) or `nil` if nothing matched.
+function skins.__fuzzy_match_skin_name(player_name, skin_name, be_noisy)
+	if select(2, skin_name:gsub("%.", "")) > 0 then
+		-- Not affected by ambiguity
+		return
+	end
+
+	for _, skin in pairs(skins.meta) do
+		if skin._legacy_name == skin_name then
+			dbgprint("Match", skin_name, skin:get_key())
+			return skin
+		end
+		--dbgprint("Try match", skin_name, skin:get_key(), skin._legacy_name)
+	end
+
+	if be_noisy then
+		minetest.log("warning", "skinsdb: cannot find matching skin '" ..
+			skin_name .. "' for player '" .. player_name .. "'.")
+	end
 end
 
 do
@@ -103,7 +144,7 @@ do
 	local skins_dir_list = minetest.get_dir_list(skins_path)
 
 	for _, fn in pairs(skins_dir_list) do
-		process_skin_texture(skins_path, fn)
+		skins.register_skin(skins_path, fn)
 	end
 end
 

textures/readme.txt

@@ -26,7 +26,7 @@ The character `_` is accepted in player names, thus it is not recommended to
 use such file names. For compatibility reasons, they are still recognized.
 
 	character_[number or name].png
-	player_[nick]_png
+	player_[nick].png
 	player_[nick]_[number or name].png
 
 ... and corresponding previews that end in `_preview.png`.

unittest.lua

@@ -0,0 +1,50 @@
+local function get_skin(skin_name)
+	local skin = skins.get(skin_name)
+		or skins.__fuzzy_match_skin_name("(unittest)", skin_name, true)
+	return skin and skin:get_key() or nil
+end
+
+local function run_unittest()
+	local PATH = ":UNITTEST:"
+
+	-- -----
+	-- `.`: Simple register + retrieve operations
+	skins.register_skin(PATH, "player.DotSep.png")
+	skins.register_skin(PATH, "player._DotSep_666_.1.png")
+
+	assert(get_skin("player.DotSep"))
+	assert(get_skin("player._DotSep_666_.1"))
+	assert(get_skin("player.DotSep.1") == nil)
+
+	-- -----
+	-- Ambiguous skin names (filenames without extension). Register + retrieve
+	skins.new("player_AmbSki")
+	skins.new("player_AmbSki_1")
+	skins.new("player_AmbSki_666_1")
+
+	assert(get_skin("player_AmbSki"))
+	assert(get_skin("player_AmbSki_") == nil)
+	assert(get_skin("player_AmbSki_1"))
+	assert(get_skin("player_AmbSki_666_1"))
+	-- There are no `__` patterns as they were silently removed by string.split
+
+
+	-- -----
+	-- Mod Storage backwards compatibility
+	-- Match the old `_` notation to `.`-separated skins
+	skins.register_skin(PATH, "player.ComPat42.png")
+	skins.register_skin(PATH, "player.ComPat42.5.png")
+	skins.register_skin(PATH, "player._Com_Pat_42.png")
+	skins.register_skin(PATH, "player._Com_Pat_42.1.png")
+
+	assert(get_skin("player_ComPat42") == "player.ComPat42")
+	assert(get_skin("player_ComPat42_5") == "player.ComPat42.5")
+	assert(get_skin("player_Com_Pat_42") == "player._Com_Pat_42")
+	assert(get_skin("player_Com_Pat_42_1") == "player._Com_Pat_42.1")
+
+
+	error("Unittest passed! Please disable them now.")
+end
+
+run_unittest()
+