lua: expose vis:module_exist method, load lexer and lpeg module durin…

…g startup

lua/vis-std.lua

@@ -1,24 +1,6 @@
 -- standard vis event handlers
 
 vis.events.subscribe(vis.events.INIT, function()
-	local package_exist = function(name)
-		for _, searcher in ipairs(package.searchers or package.loaders) do
-			local loader = searcher(name)
-			if type(loader) == 'function' then
-				return true
-			end
-		end
-		return false
-	end
-
-	if not package_exist('lpeg') then
-		vis:info('WARNING: could not find lpeg module')
-	elseif not package_exist('lexer') then
-		vis:info('WARNING: could not find lexer module')
-	else
-		vis.lexers = require('lexer')
-	end
-
 	if os.getenv("TERM_PROGRAM") == "Apple_Terminal" then
 		vis:command("set change-256colors false");
 	end
@@ -41,7 +23,7 @@ end)
 
 vis.events.subscribe(vis.events.WIN_SYNTAX, function(win, name)
 	local lexers = vis.lexers
-	if not lexers.load then return false end
+	if not lexers then return false end
 
 	win:style_define(win.STYLE_DEFAULT, lexers.STYLE_DEFAULT or '')
 	win:style_define(win.STYLE_CURSOR, lexers.STYLE_CURSOR or '')

lua/vis.lua

@@ -5,8 +5,6 @@
 ---
 -- @type Vis
 
-vis.lexers = {}
-
 --- Map a new motion.
 --
 -- Sets up a mapping in normal, visual and operator pending mode.
@@ -64,6 +62,30 @@ vis.textobject_new = function(vis, key, textobject, help)
 	return true
 end
 
+--- Check whether a Lua module exists
+--
+-- Checks whether a subsequent @{require} call will succeed.
+-- @tparam string name the module name to check
+-- @treturn bool whether the module was found
+vis.module_exist = function(vis, name)
+	for _, searcher in ipairs(package.searchers or package.loaders) do
+		local loader = searcher(name)
+		if type(loader) == 'function' then
+			return true
+		end
+	end
+	return false
+end
+
+if not vis:module_exist('lpeg') then
+	vis:info('WARNING: could not find lpeg module')
+elseif not vis:module_exist('lexer') then
+	vis:info('WARNING: could not find lexer module')
+else
+	vis.lexers = require('lexer')
+	vis.lpeg = require('lpeg')
+end
+
 --- Events.
 --
 -- User scripts can subscribe Lua functions to certain events. Multiple functions

vis-lua.c

@@ -543,11 +543,13 @@ static const char *keymapping(Vis *vis, const char *keys, const Arg *arg) {
  * @field registers array to access the register by single letter name
  */
 /***
- * LPeg lexer support module.
- * @field lexers
+ * Scintillua lexer module.
+ * @field lexers might be `nil` if module is not found
+ */
+/***
+ * LPeg lexer module.
+ * @field lpeg might be `nil` if module is not found
  */
-
-// TODO vis.events
 
 /***
  * Create an iterator over all windows.