js: require: allow custom module search paths via mp.module_paths

DOCS/man/javascript.rst

@@ -240,6 +240,9 @@ Note: ``read_file`` and ``write_file`` throw on errors, allow text content only.
     anything from the filesystem), and returns it as a function. Very similar
     to a ``Function`` constructor, but shows at stack traces as ``fname``.
 
+``mp.module_paths``
+    Global modules search paths array for the ``require`` function (see below).
+
 Timers (global)
 ---------------
 
@@ -301,6 +304,11 @@ or ``~/x``. Otherwise, it's considered a global module id and searched at
 ``require("x")`` is searched as file ``x.js`` at those dirs, and id ``foo/x`` is
 searched as file ``x.js`` inside dir ``foo`` at those dirs.
 
+Search paths for global module id's are at the array ``mp.module_paths``, which
+is searched in order. Initially it contains one item: ``~~/scripts/modules.js``
+such that it behaves as described above. Modifying it will affect future
+``require`` calls with global module id's which are not already loaded/cached.
+
 No ``global`` variable, but a module's ``this`` at its top lexical scope is the
 global object - also in strict mode. If you have a module which needs ``global``
 as the global object, you could do ``this.global = this;`` before ``require``.

player/javascript/defaults.js

@@ -375,6 +375,8 @@ function process_timers() {
  - Module id supports mpv path enhancements, e.g. ~/foo, ~~/bar, ~~desktop/baz
  *********************************************************************/
 
+mp.module_paths = ["~~/scripts/modules.js"];  // global modules search paths
+
 // Internal meta top-dirs. Users should not rely on these names.
 var MODULES_META = "~~modules",
     SCRIPTDIR_META = "~~scriptdir",  // relative script path -> meta absolute id
@@ -389,10 +391,14 @@ function resolve_module_file(id) {
         return mp.utils.join_path(main_script[0], rest);
 
     if (base == MODULES_META) {
-        var path = mp.find_config_file("scripts/modules.js/" + rest);
-        if (!path)
-            throw(Error("Cannot find module file '" + rest + "'"));
-        return path;
+        for (var i = 0; i < mp.module_paths.length; i++) {
+            try {
+                var f = mp.utils.join_path(mp.module_paths[i], rest);
+                mp.utils.read_file(f, 1);  // throws on any error
+                return f;
+            } catch (e) {}
+        }
+        throw(Error("Cannot find module file '" + rest + "'"));
     }
 
     return id + ".js";