Repository: yt-dlp/yt-dlp
Pull request #13639 (2025-07-04 22:28:43)

[ie/youtube] Fix nsig extraction for `tce` player JS


<details open><summary>Template</summary> <!-- OPEN is intentional -->


### Before submitting a *pull request* make sure you have:
- [x] At least skimmed through [contributing guidelines](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#developer-instructions) including [yt-dlp coding conventions](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#yt-dlp-coding-conventions)
- [x] [Searched](https://github.com/yt-dlp/yt-dlp/search?q=is%3Apr&type=Issues) the bugtracker for similar pull requests

### In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under [Unlicense](http://unlicense.org/). Check those that apply and remove the others:
- [x] I am the original author of the code in this PR, and I am willing to release it under [Unlicense](http://unlicense.org/)
- [x] I am not the original author of the code in this PR, but it is in the public domain or released under [Unlicense](http://unlicense.org/): co-authored by @seproDev 

### What is the purpose of your *pull request*? Check those that apply and remove the others:
- [x] Fix or improvement to an extractor (Make sure to add/update tests)
- [x] Core bug fix/improvement

</details>



Patch:
diff --git a/yt_dlp/extractor/youtube/_video.py b/yt_dlp/extractor/youtube/_video.py
index 4689c55db..f13dbb316 100644
--- a/yt_dlp/extractor/youtube/_video.py
+++ b/yt_dlp/extractor/youtube/_video.py
@@ -26,7 +26,7 @@
 from .pot._director import initialize_pot_director
 from .pot.provider import PoTokenContext, PoTokenRequest
 from ..openload import PhantomJSwrapper
-from ...jsinterp import JSInterpreter
+from ...jsinterp import JSInterpreter, LocalNameSpace
 from ...networking.exceptions import HTTPError
 from ...utils import (
     NO_DEFAULT,
@@ -1801,6 +1801,8 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         'tablet': 'player-plasma-ias-tablet-en_US.vflset/base.js',
     }
     _INVERSE_PLAYER_JS_VARIANT_MAP = {v: k for k, v in _PLAYER_JS_VARIANT_MAP.items()}
+    _NSIG_FUNC_CACHE_ID = 'nsig func'
+    _DUMMY_STRING = 'dlp_wins'
 
     @classmethod
     def suitable(cls, url):
@@ -2204,7 +2206,7 @@ def _decrypt_nsig(self, s, video_id, player_url):
             self.to_screen(f'Extracted nsig function from {player_id}:\n{func_code[1]}\n')
 
         try:
-            extract_nsig = self._cached(self._extract_n_function_from_code, 'nsig func', player_url)
+            extract_nsig = self._cached(self._extract_n_function_from_code, self._NSIG_FUNC_CACHE_ID, player_url)
             ret = extract_nsig(jsi, func_code)(s)
         except JSInterpreter.Exception as e:
             try:
@@ -2312,16 +2314,18 @@ def _interpret_player_js_global_var(self, jscode, player_url):
 
         jsi = JSInterpreter(varcode)
         interpret_global_var = self._cached(jsi.interpret_expression, 'js global list', player_url)
-        return varname, interpret_global_var(varvalue, {}, allow_recursion=10)
+        return varname, interpret_global_var(varvalue, LocalNameSpace(), allow_recursion=10)
 
     def _fixup_n_function_code(self, argnames, nsig_code, jscode, player_url):
+        # Fixup global array
         varname, global_list = self._interpret_player_js_global_var(jscode, player_url)
         if varname and global_list:
             nsig_code = f'var {varname}={json.dumps(global_list)}; {nsig_code}'
         else:
-            varname = 'dlp_wins'
+            varname = self._DUMMY_STRING
             global_list = []
 
+        # Fixup typeof check
         undefined_idx = global_list.index('undefined') if 'undefined' in global_list else r'\d+'
         fixed_code = re.sub(
             fr'''(?x)
@@ -2334,6 +2338,32 @@ def _fixup_n_function_code(self, argnames, nsig_code, jscode, player_url):
             self.write_debug(join_nonempty(
                 'No typeof statement found in nsig function code',
                 player_url and f'        player = {player_url}', delim='\n'), only_once=True)
+
+        # Fixup global funcs
+        jsi = JSInterpreter(fixed_code)
+        cache_id = (self._NSIG_FUNC_CACHE_ID, player_url)
+        try:
+            self._cached(
+                self._extract_n_function_from_code, *cache_id)(jsi, (argnames, fixed_code))(self._DUMMY_STRING)
+        except JSInterpreter.Exception:
+            self._player_cache.pop(cache_id, None)
+
+        global_funcnames = jsi._undefined_varnames
+        debug_names = []
+        jsi = JSInterpreter(jscode)
+        for func_name in global_funcnames:
+            try:
+                func_args, func_code = jsi.extract_function_code(func_name)
+                fixed_code = f'var {func_name} = function({", ".join(func_args)}) {{ {func_code} }}; {fixed_code}'
+                debug_names.append(func_name)
+            except Exception:
+                self.report_warning(join_nonempty(
+                    f'Unable to extract global nsig function {func_name} from player JS',
+                    player_url and f'        player = {player_url}', delim='\n'), only_once=True)
+
+        if debug_names:
+            self.write_debug(f'Extracted global nsig functions: {", ".join(debug_names)}')
+
         return argnames, fixed_code
 
     def _extract_n_function_code(self, video_id, player_url):
@@ -2347,7 +2377,7 @@ def _extract_n_function_code(self, video_id, player_url):
 
         func_name = self._extract_n_function_name(jscode, player_url=player_url)
 
-        # XXX: Workaround for the global array variable and lack of `typeof` implementation
+        # XXX: Work around (a) global array variable, (b) `typeof` short-circuit, (c) global functions
         func_code = self._fixup_n_function_code(*jsi.extract_function_code(func_name), jscode, player_url)
 
         return jsi, player_id, func_code
diff --git a/yt_dlp/jsinterp.py b/yt_dlp/jsinterp.py
index b49f0cf30..f06d96832 100644
--- a/yt_dlp/jsinterp.py
+++ b/yt_dlp/jsinterp.py
@@ -222,6 +222,14 @@ def __setitem__(self, key, value):
     def __delitem__(self, key):
         raise NotImplementedError('Deleting is not supported')
 
+    def set_local(self, key, value):
+        self.maps[0][key] = value
+
+    def get_local(self, key):
+        if key in self.maps[0]:
+            return self.maps[0][key]
+        return JS_Undefined
+
 
 class Debugger:
     import sys
@@ -271,6 +279,7 @@ class JSInterpreter:
     def __init__(self, code, objects=None):
         self.code, self._functions = code, {}
         self._objects = {} if objects is None else objects
+        self._undefined_varnames = set()
 
     class Exception(ExtractorError):  # noqa: A001
         def __init__(self, msg, expr=None, *args, **kwargs):
@@ -381,7 +390,7 @@ def _dump(self, obj, namespace):
             return self._named_object(namespace, obj)
 
     @Debugger.wrap_interpreter
-    def interpret_statement(self, stmt, local_vars, allow_recursion=100):
+    def interpret_statement(self, stmt, local_vars, allow_recursion=100, _is_var_declaration=False):
         if allow_recursion < 0:
             raise self.Exception('Recursion limit reached')
         allow_recursion -= 1
@@ -401,6 +410,7 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
             if m.group('throw'):
                 raise JS_Throw(self.interpret_expression(expr, local_vars, allow_recursion))
             should_return = not m.group('var')
+            _is_var_declaration = _is_var_declaration or bool(m.group('var'))
         if not expr:
             return None, should_return
 
@@ -585,7 +595,8 @@ def dict_item(key, val):
         sub_expressions = list(self._separate(expr))
         if len(sub_expressions) > 1:
             for sub_expr in sub_expressions:
-                ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
+                ret, should_abort = self.interpret_statement(
+                    sub_expr, local_vars, allow_recursion, _is_var_declaration=_is_var_declaration)
                 if should_abort:
                     return ret, True
             return ret, False
@@ -599,8 +610,12 @@ def dict_item(key, val):
             left_val = local_vars.get(m.group('out'))
 
             if not m.group('index'):
-                local_vars[m.group('out')] = self._operator(
+                eval_result = self._operator(
                     m.group('op'), left_val, m.group('expr'), expr, local_vars, allow_recursion)
+                if _is_var_declaration:
+                    local_vars.set_local(m.group('out'), eval_result)
+                else:
+                    local_vars[m.group('out')] = eval_result
                 return local_vars[m.group('out')], should_return
             elif left_val in (None, JS_Undefined):
                 raise self.Exception(f'Cannot index undefined variable {m.group("out")}', expr)
@@ -654,7 +669,18 @@ def dict_item(key, val):
             return float('NaN'), should_return
 
         elif m and m.group('return'):
-            return local_vars.get(m.group('name'), JS_Undefined), should_return
+            var = m.group('name')
+            # Declared variables
+            if _is_var_declaration:
+                ret = local_vars.get_local(var)
+                # Register varname in local namespace
+                # Set value as JS_Undefined or its pre-existing value
+                local_vars.set_local(var, ret)
+            else:
+                ret = local_vars.get(var, JS_Undefined)
+                if ret is JS_Undefined:
+                    self._undefined_varnames.add(var)
+            return ret, should_return
 
         with contextlib.suppress(ValueError):
             return json.loads(js_to_json(expr, strict=True)), should_return


Test patch:
diff --git a/test/test_jsinterp.py b/test/test_jsinterp.py
index 4268e890b..a1088cea4 100644
--- a/test/test_jsinterp.py
+++ b/test/test_jsinterp.py
@@ -490,6 +490,52 @@ def test_increment_decrement(self):
         self._test('function f() { var a = "test--"; return a; }', 'test--')
         self._test('function f() { var b = 1; var a = "b--"; return a; }', 'b--')
 
+    def test_nested_function_scoping(self):
+        self._test(R'''
+            function f() {
+                var g = function() {
+                    var P = 2;
+                    return P;
+                };
+                var P = 1;
+                g();
+                return P;
+            }
+        ''', 1)
+        self._test(R'''
+            function f() {
+                var x = function() {
+                    for (var w = 1, M = []; w < 2; w++) switch (w) {
+                        case 1:
+                            M.push("a");
+                        case 2:
+                            M.push("b");
+                    }
+                    return M
+                };
+                var w = "c";
+                var M = "d";
+                var y = x();
+                y.push(w);
+                y.push(M);
+                return y;
+            }
+        ''', ['a', 'b', 'c', 'd'])
+        self._test(R'''
+            function f() {
+                var P, Q;
+                var z = 100;
+                var g = function() {
+                    var P, Q; P = 2; Q = 15;
+                    z = 0;
+                    return P+Q;
+                };
+                P = 1; Q = 10;
+                var x = g(), y = 3;
+                return P+Q+x+y+z;
+            }
+        ''', 31)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/test/test_youtube_signature.py b/test/test_youtube_signature.py
index 5e6792679..98607df55 100644
--- a/test/test_youtube_signature.py
+++ b/test/test_youtube_signature.py
@@ -333,6 +333,46 @@
         'https://www.youtube.com/s/player/fc2a56a5/tv-player-ias.vflset/tv-player-ias.js',
         'qTKWg_Il804jd2kAC', 'OtUAm2W6gyzJjB9u',
     ),
+    (
+        'https://www.youtube.com/s/player/a74bf670/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', 'hQP7k1hA22OrNTnq',
+    ),
+    (
+        'https://www.youtube.com/s/player/6275f73c/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '-I03XF0iyf6I_X0A',
+    ),
+    (
+        'https://www.youtube.com/s/player/20c72c18/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '-I03XF0iyf6I_X0A',
+    ),
+    (
+        'https://www.youtube.com/s/player/9fe2e06e/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '6r5ekNIiEMPutZy',
+    ),
+    (
+        'https://www.youtube.com/s/player/680f8c75/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '0ml9caTwpa55Jf',
+    ),
+    (
+        'https://www.youtube.com/s/player/14397202/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', 'ozZFAN21okDdJTa',
+    ),
+    (
+        'https://www.youtube.com/s/player/5dcb2c1f/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', 'p7iTbRZDYAF',
+    ),
+    (
+        'https://www.youtube.com/s/player/a10d7fcc/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '9Zue7DDHJSD',
+    ),
+    (
+        'https://www.youtube.com/s/player/8e20cb06/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', '5-4tTneTROTpMzba',
+    ),
+    (
+        'https://www.youtube.com/s/player/e12fbea4/player_ias_tce.vflset/en_US/base.js',
+        'kM5r52fugSZRAKHfo3', 'XkeRfXIPOkSwfg',
+    ),
 ]