Support configurable extra plugin lookup path (#2693)

* plugin loader(feat): support loading plugins from user defined directories
Extra plugin lookup paths can be set in global reader setting via key
`extra_plugin_paths`. Value of the key can either be a string or an array
of strings.
* build(fix): also purge non-exist plugins on build
* plugin: migrate debug plugin to menu sorter

Makefile

@@ -79,6 +79,9 @@ endif
 	@echo "[*] Install plugins"
 	@# TODO: link istead of cp?
 	$(RCP) plugins/* $(INSTALL_DIR)/koreader/plugins/
+	@# purge deleted plugins
+	for d in $$(ls $(INSTALL_DIR)/koreader/plugins); do \
+		test -d plugins/$$d || rm -rf $(INSTALL_DIR)/koreader/plugins/$$d ; done
 	@echo "[*] Installresources"
 	$(RCP) -pL resources/fonts/* $(INSTALL_DIR)/koreader/fonts/
 	install -d $(INSTALL_DIR)/koreader/{screenshots,data/{dict,tessdata},fonts/host,ota}

frontend/pluginloader.lua

@@ -1,42 +1,66 @@
 local lfs = require("libs/libkoreader-lfs")
 local logger = require("logger")
 
-local PluginLoader = {
-    plugin_path = "plugins"
-}
+local DEFAULT_PLUGIN_PATH = "plugins"
+
+local PluginLoader = {}
 
 function PluginLoader:loadPlugins()
     if self.plugins then return self.plugins end
 
     self.plugins = {}
-    for f in lfs.dir(self.plugin_path) do
-        local path = self.plugin_path.."/"..f
-        local mode = lfs.attributes(path, "mode")
-        -- valid koreader plugin directory
-        if mode == "directory" and f:find(".+%.koplugin$") then
-            local mainfile = path.."/".."main.lua"
+    local lookup_path_list = { DEFAULT_PLUGIN_PATH }
+    local extra_paths = G_reader_settings:readSetting("extra_plugin_paths")
+    if extra_paths then
+        if type(extra_paths) == "string" then
+            extra_paths = { extra_paths }
+        end
+        if type(extra_paths) == "table" then
+            for _,extra_path in ipairs(extra_paths) do
+                local extra_path_mode = lfs.attributes(extra_path, "mode")
+                if extra_path_mode == "directory" and extra_path ~= DEFAULT_PLUGIN_PATH then
+                    table.insert(lookup_path_list, extra_path)
+                end
+            end
+        else
+            logger.err("extra_plugin_paths config only accepts string or table value")
+        end
+    end
+
+    -- keep reference to old value so they can be restored later
     local package_path = package.path
     local package_cpath = package.cpath
-            package.path = path.."/?.lua;"..package.path
-            package.cpath = path.."/lib/?.so;"..package.cpath
+
+    for _,lookup_path in ipairs(lookup_path_list) do
+        logger.info('Loading plugins from directory:', lookup_path)
+        for entry in lfs.dir(lookup_path) do
+            local plugin_root = lookup_path.."/"..entry
+            local mode = lfs.attributes(plugin_root, "mode")
+            -- valid koreader plugin directory
+            if mode == "directory" and entry:find(".+%.koplugin$") then
+                local mainfile = plugin_root.."/main.lua"
+                package.path = string.format("%s/?.lua;%s", plugin_root, package_path)
+                package.cpath = string.format("%s/lib/?.so;%s", plugin_root, package_cpath)
                 local ok, plugin_module = pcall(dofile, mainfile)
                 if not ok or not plugin_module then
                     logger.warn("Error when loading", mainfile, plugin_module)
                 elseif type(plugin_module.disabled) ~= "boolean" or not plugin_module.disabled then
-                package.path = package_path
-                package.cpath = package_cpath
-                plugin_module.path = path
-                plugin_module.name = plugin_module.name or path:match("/(.-)%.koplugin")
+                    plugin_module.path = plugin_root
+                    plugin_module.name = plugin_module.name or plugin_root:match("/(.-)%.koplugin")
                     table.insert(self.plugins, plugin_module)
                 else
                     logger.info("Plugin ", mainfile, " has been disabled.")
                 end
+                package.path = package_path
+                package.cpath = package_cpath
+            end
         end
     end
 
+    -- set package path for all loaded plugins
     for _,plugin in ipairs(self.plugins) do
-        package.path = package.path..";"..plugin.path.."/?.lua"
-        package.cpath = package.cpath..";"..plugin.path.."/lib/?.so"
+        package.path = string.format("%s;%s/?.lua", package.path, plugin.path)
+        package.cpath = string.format("%s;%s/lib/?.so", package.cpath, plugin.path)
     end
 
     table.sort(self.plugins, function(v1,v2) return v1.path < v2.path end)

frontend/ui/elements/reader_menu_order.lua

@@ -23,7 +23,6 @@ local order = {
         "highlight_options",
         "change_font",
         "hyphenation",
-        "read_timer",
     },
     setting = {
         "read_from_right_to_left",
@@ -43,6 +42,7 @@ local order = {
         "status_bar",
     },
     tools = {
+        "read_timer",
         "calibre_wireless_connection",
         "evernote",
         "goodreads",

plugins/hello.koplugin/main.lua

@@ -1,4 +1,9 @@
-local InfoMessage = require("ui/widget/infomessage")
+-- This is a debug plugin, remove the following if block to enable it
+if true then
+    return { disabled = true, }
+end
+
+local InfoMessage = require("ui/widget/infomessage")  -- luacheck:ignore
 local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local _ = require("gettext")
@@ -6,22 +11,21 @@ local _ = require("gettext")
 local Hello = WidgetContainer:new{
     name = 'Hello',
     is_doc_only = false,
-    disabled = true,  -- This is a debug plugin
 }
 
 function Hello:init()
     self.ui.menu:registerToMainMenu(self)
 end
 
-function Hello:addToMainMenu(tab_item_table)
-    table.insert(tab_item_table.plugins, {
+function Hello:addToMainMenu(menu_items)
+    menu_items.hello_world = {
         text = _("Hello World"),
         callback = function()
             UIManager:show(InfoMessage:new{
-                text = _("Hello, docless plugin world"),
+                text = _("Hello, plugin world"),
             })
         end,
-    })
+    }
 end
 
 return Hello

plugins/kobolight.koplugin/main.lua

@@ -9,7 +9,6 @@ local ConfirmBox = require("ui/widget/confirmbox")
 local ImageWidget = require("ui/widget/imagewidget")
 local InfoMessage = require("ui/widget/infomessage")
 local Notification = require("ui/widget/notification")
-local PluginLoader = require("pluginloader")
 local Screen = require("device").screen
 local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
@@ -165,7 +164,7 @@ function KoboLight:addToMainMenu(menu_items)
         text = _("Frontlight gesture controller"),
         callback = function()
             local image = ImageWidget:new{
-                file = PluginLoader.plugin_path .. "/kobolight.koplugin/demo.png",
+                file = self.path .. "/demo.png",
                 height = Screen:getHeight(),
                 width = Screen:getWidth(),
                 scale_factor = 0,

plugins/timesync.koplugin/main.lua

@@ -1,4 +1,3 @@
-
 local Device = require("device")
 
 local command