X-Git-Url: https://jfr.im/git/yt-dlp.git/blobdiff_plain/86e5f3ed2e6e71eb81ea4c9e26288f16119ffd0c..c4b87dd885ee5391e5f481e7c8bd550a7c543623:/yt_dlp/jsinterp.py

diff --git a/yt_dlp/jsinterp.py b/yt_dlp/jsinterp.py
index 3695a282d..bda3fb459 100644
--- a/yt_dlp/jsinterp.py
+++ b/yt_dlp/jsinterp.py
@@ -1,31 +1,142 @@
-from collections.abc import MutableMapping
+import collections
+import contextlib
+import itertools
 import json
+import math
 import operator
 import re
 
 from .utils import (
+    NO_DEFAULT,
     ExtractorError,
+    function_with_repr,
+    js_to_json,
     remove_quotes,
+    truncate_string,
+    unified_timestamp,
+    write_string,
 )
 
-_OPERATORS = [
-    ('|', operator.or_),
-    ('^', operator.xor),
-    ('&', operator.and_),
-    ('>>', operator.rshift),
-    ('<<', operator.lshift),
-    ('-', operator.sub),
-    ('+', operator.add),
-    ('%', operator.mod),
-    ('/', operator.truediv),
-    ('*', operator.mul),
-]
-_ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
-_ASSIGN_OPERATORS.append(('=', (lambda cur, right: right)))
 
-_NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
+def _js_bit_op(op):
+    def zeroise(x):
+        if x in (None, JS_Undefined):
+            return 0
+        with contextlib.suppress(TypeError):
+            if math.isnan(x):  # NB: NaN cannot be checked by membership
+                return 0
+        return x
 
-_MATCHING_PARENS = dict(zip('({[', ')}]'))
+    def wrapped(a, b):
+        return op(zeroise(a), zeroise(b)) & 0xffffffff
+
+    return wrapped
+
+
+def _js_arith_op(op):
+
+    def wrapped(a, b):
+        if JS_Undefined in (a, b):
+            return float('nan')
+        return op(a or 0, b or 0)
+
+    return wrapped
+
+
+def _js_div(a, b):
+    if JS_Undefined in (a, b) or not (a or b):
+        return float('nan')
+    return (a or 0) / b if b else float('inf')
+
+
+def _js_mod(a, b):
+    if JS_Undefined in (a, b) or not b:
+        return float('nan')
+    return (a or 0) % b
+
+
+def _js_exp(a, b):
+    if not b:
+        return 1  # even 0 ** 0 !!
+    elif JS_Undefined in (a, b):
+        return float('nan')
+    return (a or 0) ** b
+
+
+def _js_eq_op(op):
+
+    def wrapped(a, b):
+        if {a, b} <= {None, JS_Undefined}:
+            return op(a, a)
+        return op(a, b)
+
+    return wrapped
+
+
+def _js_comp_op(op):
+
+    def wrapped(a, b):
+        if JS_Undefined in (a, b):
+            return False
+        if isinstance(a, str) or isinstance(b, str):
+            return op(str(a or 0), str(b or 0))
+        return op(a or 0, b or 0)
+
+    return wrapped
+
+
+def _js_ternary(cndn, if_true=True, if_false=False):
+    """Simulate JS's ternary operator (cndn?if_true:if_false)"""
+    if cndn in (False, None, 0, '', JS_Undefined):
+        return if_false
+    with contextlib.suppress(TypeError):
+        if math.isnan(cndn):  # NB: NaN cannot be checked by membership
+            return if_false
+    return if_true
+
+
+# Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
+_OPERATORS = {  # None => Defined in JSInterpreter._operator
+    '?': None,
+    '??': None,
+    '||': None,
+    '&&': None,
+
+    '|': _js_bit_op(operator.or_),
+    '^': _js_bit_op(operator.xor),
+    '&': _js_bit_op(operator.and_),
+
+    '===': operator.is_,
+    '!==': operator.is_not,
+    '==': _js_eq_op(operator.eq),
+    '!=': _js_eq_op(operator.ne),
+
+    '<=': _js_comp_op(operator.le),
+    '>=': _js_comp_op(operator.ge),
+    '<': _js_comp_op(operator.lt),
+    '>': _js_comp_op(operator.gt),
+
+    '>>': _js_bit_op(operator.rshift),
+    '<<': _js_bit_op(operator.lshift),
+
+    '+': _js_arith_op(operator.add),
+    '-': _js_arith_op(operator.sub),
+
+    '*': _js_arith_op(operator.mul),
+    '%': _js_mod,
+    '/': _js_div,
+    '**': _js_exp,
+}
+
+_COMP_OPERATORS = {'===', '!==', '==', '!=', '<=', '>=', '<', '>'}
+
+_NAME_RE = r'[a-zA-Z_$][\w$]*'
+_MATCHING_PARENS = dict(zip(*zip('()', '{}', '[]')))
+_QUOTES = '\'"/'
+
+
+class JS_Undefined:
+    pass
 
 
 class JS_Break(ExtractorError):
@@ -38,66 +149,125 @@ def __init__(self):
         ExtractorError.__init__(self, 'Invalid continue')
 
 
-class LocalNameSpace(MutableMapping):
-    def __init__(self, *stack):
-        self.stack = tuple(stack)
+class JS_Throw(ExtractorError):
+    def __init__(self, e):
+        self.error = e
+        ExtractorError.__init__(self, f'Uncaught exception {e}')
 
-    def __getitem__(self, key):
-        for scope in self.stack:
-            if key in scope:
-                return scope[key]
-        raise KeyError(key)
 
+class LocalNameSpace(collections.ChainMap):
     def __setitem__(self, key, value):
-        for scope in self.stack:
+        for scope in self.maps:
             if key in scope:
                 scope[key] = value
-                break
-        else:
-            self.stack[0][key] = value
-        return value
+                return
+        self.maps[0][key] = value
 
     def __delitem__(self, key):
         raise NotImplementedError('Deleting is not supported')
 
-    def __iter__(self):
-        for scope in self.stack:
-            yield from scope
 
-    def __len__(self, key):
-        return len(iter(self))
+class Debugger:
+    import sys
+    ENABLED = False and 'pytest' in sys.modules
 
-    def __repr__(self):
-        return f'LocalNameSpace{self.stack}'
+    @staticmethod
+    def write(*args, level=100):
+        write_string(f'[debug] JS: {"  " * (100 - level)}'
+                     f'{" ".join(truncate_string(str(x), 50, 50) for x in args)}\n')
+
+    @classmethod
+    def wrap_interpreter(cls, f):
+        def interpret_statement(self, stmt, local_vars, allow_recursion, *args, **kwargs):
+            if cls.ENABLED and stmt.strip():
+                cls.write(stmt, level=allow_recursion)
+            try:
+                ret, should_ret = f(self, stmt, local_vars, allow_recursion, *args, **kwargs)
+            except Exception as e:
+                if cls.ENABLED:
+                    if isinstance(e, ExtractorError):
+                        e = e.orig_msg
+                    cls.write('=> Raises:', e, '<-|', stmt, level=allow_recursion)
+                raise
+            if cls.ENABLED and stmt.strip():
+                if should_ret or not repr(ret) == stmt:
+                    cls.write(['->', '=>'][should_ret], repr(ret), '<-|', stmt, level=allow_recursion)
+            return ret, should_ret
+        return interpret_statement
 
 
 class JSInterpreter:
+    __named_object_counter = 0
+
+    _RE_FLAGS = {
+        # special knowledge: Python's re flags are bitmask values, current max 128
+        # invent new bitmask values well above that for literal parsing
+        # TODO: new pattern class to execute matches with these flags
+        'd': 1024,  # Generate indices for substring matches
+        'g': 2048,  # Global search
+        'i': re.I,  # Case-insensitive search
+        'm': re.M,  # Multi-line search
+        's': re.S,  # Allows . to match newline characters
+        'u': re.U,  # Treat a pattern as a sequence of unicode code points
+        'y': 4096,  # Perform a "sticky" search that matches starting at the current position in the target string
+    }
+
     def __init__(self, code, objects=None):
-        if objects is None:
-            objects = {}
-        self.code = code
-        self._functions = {}
-        self._objects = objects
-        self.__named_object_counter = 0
+        self.code, self._functions = code, {}
+        self._objects = {} if objects is None else objects
+
+    class Exception(ExtractorError):
+        def __init__(self, msg, expr=None, *args, **kwargs):
+            if expr is not None:
+                msg = f'{msg.rstrip()} in: {truncate_string(expr, 50, 50)}'
+            super().__init__(msg, *args, **kwargs)
 
     def _named_object(self, namespace, obj):
         self.__named_object_counter += 1
         name = f'__yt_dlp_jsinterp_obj{self.__named_object_counter}'
+        if callable(obj) and not isinstance(obj, function_with_repr):
+            obj = function_with_repr(obj, f'F<{self.__named_object_counter}>')
         namespace[name] = obj
         return name
 
+    @classmethod
+    def _regex_flags(cls, expr):
+        flags = 0
+        if not expr:
+            return flags, expr
+        for idx, ch in enumerate(expr):
+            if ch not in cls._RE_FLAGS:
+                break
+            flags |= cls._RE_FLAGS[ch]
+        return flags, expr[idx + 1:]
+
     @staticmethod
     def _separate(expr, delim=',', max_split=None):
+        OP_CHARS = '+-*/%&|^=<>!,;{}:['
         if not expr:
             return
         counters = {k: 0 for k in _MATCHING_PARENS.values()}
         start, splits, pos, delim_len = 0, 0, 0, len(delim) - 1
+        in_quote, escaping, after_op, in_regex_char_group = None, False, True, False
         for idx, char in enumerate(expr):
-            if char in _MATCHING_PARENS:
+            if not in_quote and char in _MATCHING_PARENS:
                 counters[_MATCHING_PARENS[char]] += 1
-            elif char in counters:
-                counters[char] -= 1
-            if char != delim[pos] or any(counters.values()):
+            elif not in_quote and char in counters:
+                # Something's wrong if we get negative, but ignore it anyway
+                if counters[char]:
+                    counters[char] -= 1
+            elif not escaping:
+                if char in _QUOTES and in_quote in (char, None):
+                    if in_quote or after_op or char != '/':
+                        in_quote = None if in_quote and not in_regex_char_group else char
+                elif in_quote == '/' and char in '[]':
+                    in_regex_char_group = char == '['
+            escaping = not escaping and in_quote and char == '\\'
+            in_unary_op = (not in_quote and not in_regex_char_group
+                           and after_op not in (True, False) and char in '-+')
+            after_op = char if (not in_quote and char in OP_CHARS) else (char.isspace() and after_op)
+
+            if char != delim[pos] or any(counters.values()) or in_quote or in_unary_op:
                 pos = 0
                 continue
             elif pos != delim_len:
@@ -110,122 +280,224 @@ def _separate(expr, delim=',', max_split=None):
                 break
         yield expr[start:]
 
-    @staticmethod
-    def _separate_at_paren(expr, delim):
-        separated = list(JSInterpreter._separate(expr, delim, 1))
+    @classmethod
+    def _separate_at_paren(cls, expr, delim=None):
+        if delim is None:
+            delim = expr and _MATCHING_PARENS[expr[0]]
+        separated = list(cls._separate(expr, delim, 1))
         if len(separated) < 2:
-            raise ExtractorError(f'No terminating paren {delim} in {expr}')
+            raise cls.Exception(f'No terminating paren {delim}', expr)
         return separated[0][1:].strip(), separated[1].strip()
 
+    def _operator(self, op, left_val, right_expr, expr, local_vars, allow_recursion):
+        if op in ('||', '&&'):
+            if (op == '&&') ^ _js_ternary(left_val):
+                return left_val  # short circuiting
+        elif op == '??':
+            if left_val not in (None, JS_Undefined):
+                return left_val
+        elif op == '?':
+            right_expr = _js_ternary(left_val, *self._separate(right_expr, ':', 1))
+
+        right_val = self.interpret_expression(right_expr, local_vars, allow_recursion)
+        if not _OPERATORS.get(op):
+            return right_val
+
+        try:
+            return _OPERATORS[op](left_val, right_val)
+        except Exception as e:
+            raise self.Exception(f'Failed to evaluate {left_val!r} {op} {right_val!r}', expr, cause=e)
+
+    def _index(self, obj, idx, allow_undefined=False):
+        if idx == 'length':
+            return len(obj)
+        try:
+            return obj[int(idx)] if isinstance(obj, list) else obj[idx]
+        except Exception as e:
+            if allow_undefined:
+                return JS_Undefined
+            raise self.Exception(f'Cannot get index {idx}', repr(obj), cause=e)
+
+    def _dump(self, obj, namespace):
+        try:
+            return json.dumps(obj)
+        except TypeError:
+            return self._named_object(namespace, obj)
+
+    @Debugger.wrap_interpreter
     def interpret_statement(self, stmt, local_vars, allow_recursion=100):
         if allow_recursion < 0:
-            raise ExtractorError('Recursion limit reached')
+            raise self.Exception('Recursion limit reached')
+        allow_recursion -= 1
+
+        should_return = False
+        sub_statements = list(self._separate(stmt, ';')) or ['']
+        expr = stmt = sub_statements.pop().strip()
 
-        sub_statements = list(self._separate(stmt, ';'))
-        stmt = (sub_statements or ['']).pop()
         for sub_stmt in sub_statements:
-            ret, should_abort = self.interpret_statement(sub_stmt, local_vars, allow_recursion - 1)
-            if should_abort:
-                return ret
+            ret, should_return = self.interpret_statement(sub_stmt, local_vars, allow_recursion)
+            if should_return:
+                return ret, should_return
 
-        should_abort = False
-        stmt = stmt.lstrip()
-        stmt_m = re.match(r'var\s', stmt)
-        if stmt_m:
-            expr = stmt[len(stmt_m.group(0)):]
-        else:
-            return_m = re.match(r'return(?:\s+|$)', stmt)
-            if return_m:
-                expr = stmt[len(return_m.group(0)):]
-                should_abort = True
+        m = re.match(r'(?P<var>(?:var|const|let)\s)|return(?:\s+|(?=["\'])|$)|(?P<throw>throw\s+)', stmt)
+        if m:
+            expr = stmt[len(m.group(0)):].strip()
+            if m.group('throw'):
+                raise JS_Throw(self.interpret_expression(expr, local_vars, allow_recursion))
+            should_return = not m.group('var')
+        if not expr:
+            return None, should_return
+
+        if expr[0] in _QUOTES:
+            inner, outer = self._separate(expr, expr[0], 1)
+            if expr[0] == '/':
+                flags, outer = self._regex_flags(outer)
+                # We don't support regex methods yet, so no point compiling it
+                inner = f'{inner}/{flags}'
+                # Avoid https://github.com/python/cpython/issues/74534
+                # inner = re.compile(inner[1:].replace('[[', r'[\['), flags=flags)
             else:
-                # Try interpreting it as an expression
-                expr = stmt
-
-        v = self.interpret_expression(expr, local_vars, allow_recursion)
-        return v, should_abort
+                inner = json.loads(js_to_json(f'{inner}{expr[0]}', strict=True))
+            if not outer:
+                return inner, should_return
+            expr = self._named_object(local_vars, inner) + outer
+
+        if expr.startswith('new '):
+            obj = expr[4:]
+            if obj.startswith('Date('):
+                left, right = self._separate_at_paren(obj[4:])
+                date = unified_timestamp(
+                    self.interpret_expression(left, local_vars, allow_recursion), False)
+                if date is None:
+                    raise self.Exception(f'Failed to parse date {left!r}', expr)
+                expr = self._dump(int(date * 1000), local_vars) + right
+            else:
+                raise self.Exception(f'Unsupported object {obj}', expr)
 
-    def interpret_expression(self, expr, local_vars, allow_recursion):
-        expr = expr.strip()
-        if expr == '':  # Empty expression
-            return None
+        if expr.startswith('void '):
+            left = self.interpret_expression(expr[5:], local_vars, allow_recursion)
+            return None, should_return
 
         if expr.startswith('{'):
-            inner, outer = self._separate_at_paren(expr, '}')
-            inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion - 1)
+            inner, outer = self._separate_at_paren(expr)
+            # try for object expression (Map)
+            sub_expressions = [list(self._separate(sub_expr.strip(), ':', 1)) for sub_expr in self._separate(inner)]
+            if all(len(sub_expr) == 2 for sub_expr in sub_expressions):
+                def dict_item(key, val):
+                    val = self.interpret_expression(val, local_vars, allow_recursion)
+                    if re.match(_NAME_RE, key):
+                        return key, val
+                    return self.interpret_expression(key, local_vars, allow_recursion), val
+
+                return dict(dict_item(k, v) for k, v in sub_expressions), should_return
+
+            inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion)
             if not outer or should_abort:
-                return inner
+                return inner, should_abort or should_return
             else:
-                expr = json.dumps(inner) + outer
+                expr = self._dump(inner, local_vars) + outer
 
         if expr.startswith('('):
-            inner, outer = self._separate_at_paren(expr, ')')
-            inner = self.interpret_expression(inner, local_vars, allow_recursion)
-            if not outer:
-                return inner
+            inner, outer = self._separate_at_paren(expr)
+            inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion)
+            if not outer or should_abort:
+                return inner, should_abort or should_return
             else:
-                expr = json.dumps(inner) + outer
+                expr = self._dump(inner, local_vars) + outer
 
         if expr.startswith('['):
-            inner, outer = self._separate_at_paren(expr, ']')
+            inner, outer = self._separate_at_paren(expr)
             name = self._named_object(local_vars, [
                 self.interpret_expression(item, local_vars, allow_recursion)
                 for item in self._separate(inner)])
             expr = name + outer
 
-        m = re.match(r'try\s*', expr)
-        if m:
-            if expr[m.end()] == '{':
-                try_expr, expr = self._separate_at_paren(expr[m.end():], '}')
-            else:
-                try_expr, expr = expr[m.end() - 1:], ''
-            ret, should_abort = self.interpret_statement(try_expr, local_vars, allow_recursion - 1)
+        m = re.match(r'''(?x)
+                (?P<try>try)\s*\{|
+                (?P<if>if)\s*\(|
+                (?P<switch>switch)\s*\(|
+                (?P<for>for)\s*\(
+                ''', expr)
+        md = m.groupdict() if m else {}
+        if md.get('if'):
+            cndn, expr = self._separate_at_paren(expr[m.end() - 1:])
+            if_expr, expr = self._separate_at_paren(expr.lstrip())
+            # TODO: "else if" is not handled
+            else_expr = None
+            m = re.match(r'else\s*{', expr)
+            if m:
+                else_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+            cndn = _js_ternary(self.interpret_expression(cndn, local_vars, allow_recursion))
+            ret, should_abort = self.interpret_statement(
+                if_expr if cndn else else_expr, local_vars, allow_recursion)
             if should_abort:
-                return ret
-            return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
+                return ret, True
 
-        m = re.match(r'catch\s*\(', expr)
-        if m:
-            # We ignore the catch block
-            _, expr = self._separate_at_paren(expr, '}')
-            return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
+        if md.get('try'):
+            try_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+            err = None
+            try:
+                ret, should_abort = self.interpret_statement(try_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
+            except Exception as e:
+                # XXX: This works for now, but makes debugging future issues very hard
+                err = e
+
+            pending = (None, False)
+            m = re.match(fr'catch\s*(?P<err>\(\s*{_NAME_RE}\s*\))?\{{', expr)
+            if m:
+                sub_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+                if err:
+                    catch_vars = {}
+                    if m.group('err'):
+                        catch_vars[m.group('err')] = err.error if isinstance(err, JS_Throw) else err
+                    catch_vars = local_vars.new_child(catch_vars)
+                    err, pending = None, self.interpret_statement(sub_expr, catch_vars, allow_recursion)
+
+            m = re.match(r'finally\s*\{', expr)
+            if m:
+                sub_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+                ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
 
-        m = re.match(r'for\s*\(', expr)
-        if m:
-            constructor, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
+            ret, should_abort = pending
+            if should_abort:
+                return ret, True
+
+            if err:
+                raise err
+
+        elif md.get('for'):
+            constructor, remaining = self._separate_at_paren(expr[m.end() - 1:])
             if remaining.startswith('{'):
-                body, expr = self._separate_at_paren(remaining, '}')
+                body, expr = self._separate_at_paren(remaining)
             else:
-                m = re.match(r'switch\s*\(', remaining)  # FIXME
-                if m:
-                    switch_val, remaining = self._separate_at_paren(remaining[m.end() - 1:], ')')
+                switch_m = re.match(r'switch\s*\(', remaining)  # FIXME
+                if switch_m:
+                    switch_val, remaining = self._separate_at_paren(remaining[switch_m.end() - 1:])
                     body, expr = self._separate_at_paren(remaining, '}')
                     body = 'switch(%s){%s}' % (switch_val, body)
                 else:
                     body, expr = remaining, ''
             start, cndn, increment = self._separate(constructor, ';')
-            if self.interpret_statement(start, local_vars, allow_recursion - 1)[1]:
-                raise ExtractorError(
-                    f'Premature return in the initialization of a for loop in {constructor!r}')
+            self.interpret_expression(start, local_vars, allow_recursion)
             while True:
-                if not self.interpret_expression(cndn, local_vars, allow_recursion):
+                if not _js_ternary(self.interpret_expression(cndn, local_vars, allow_recursion)):
                     break
                 try:
-                    ret, should_abort = self.interpret_statement(body, local_vars, allow_recursion - 1)
+                    ret, should_abort = self.interpret_statement(body, local_vars, allow_recursion)
                     if should_abort:
-                        return ret
+                        return ret, True
                 except JS_Break:
                     break
                 except JS_Continue:
                     pass
-                if self.interpret_statement(increment, local_vars, allow_recursion - 1)[1]:
-                    raise ExtractorError(
-                        f'Premature return in the initialization of a for loop in {constructor!r}')
-            return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
+                self.interpret_expression(increment, local_vars, allow_recursion)
 
-        m = re.match(r'switch\s*\(', expr)
-        if m:
-            switch_val, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
+        elif md.get('switch'):
+            switch_val, remaining = self._separate_at_paren(expr[m.end() - 1:])
             switch_val = self.interpret_expression(switch_val, local_vars, allow_recursion)
             body, expr = self._separate_at_paren(remaining, '}')
             items = body.replace('default:', 'case default:').split('case ')[1:]
@@ -236,24 +508,31 @@ def interpret_expression(self, expr, local_vars, allow_recursion):
                     if default:
                         matched = matched or case == 'default'
                     elif not matched:
-                        matched = case != 'default' and switch_val == self.interpret_expression(case, local_vars, allow_recursion)
+                        matched = (case != 'default'
+                                   and switch_val == self.interpret_expression(case, local_vars, allow_recursion))
                     if not matched:
                         continue
                     try:
-                        ret, should_abort = self.interpret_statement(stmt, local_vars, allow_recursion - 1)
+                        ret, should_abort = self.interpret_statement(stmt, local_vars, allow_recursion)
                         if should_abort:
                             return ret
                     except JS_Break:
                         break
                 if matched:
                     break
-            return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
+
+        if md:
+            ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
+            return ret, should_abort or should_return
 
         # Comma separated statements
         sub_expressions = list(self._separate(expr))
-        expr = sub_expressions.pop().strip() if sub_expressions else ''
-        for sub_expr in sub_expressions:
-            self.interpret_expression(sub_expr, local_vars, allow_recursion)
+        if len(sub_expressions) > 1:
+            for sub_expr in sub_expressions:
+                ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
+            return ret, False
 
         for m in re.finditer(rf'''(?x)
                 (?P<pre_sign>\+\+|--)(?P<var1>{_NAME_RE})|
@@ -265,107 +544,123 @@ def interpret_expression(self, expr, local_vars, allow_recursion):
             local_vars[var] += 1 if sign[0] == '+' else -1
             if m.group('pre_sign'):
                 ret = local_vars[var]
-            expr = expr[:start] + json.dumps(ret) + expr[end:]
-
-        for op, opfunc in _ASSIGN_OPERATORS:
-            m = re.match(rf'''(?x)
-                (?P<out>{_NAME_RE})(?:\[(?P<index>[^\]]+?)\])?
-                \s*{re.escape(op)}
-                (?P<expr>.*)$''', expr)
-            if not m:
-                continue
-            right_val = self.interpret_expression(m.group('expr'), local_vars, allow_recursion)
-
-            if m.groupdict().get('index'):
-                lvar = local_vars[m.group('out')]
-                idx = self.interpret_expression(m.group('index'), local_vars, allow_recursion)
-                if not isinstance(idx, int):
-                    raise ExtractorError(f'List indices must be integers: {idx}')
-                cur = lvar[idx]
-                val = opfunc(cur, right_val)
-                lvar[idx] = val
-                return val
-            else:
-                cur = local_vars.get(m.group('out'))
-                val = opfunc(cur, right_val)
-                local_vars[m.group('out')] = val
-                return val
+            expr = expr[:start] + self._dump(ret, local_vars) + expr[end:]
 
-        if expr.isdigit():
-            return int(expr)
-
-        if expr == 'break':
+        if not expr:
+            return None, should_return
+
+        m = re.match(fr'''(?x)
+            (?P<assign>
+                (?P<out>{_NAME_RE})(?:\[(?P<index>[^\]]+?)\])?\s*
+                (?P<op>{"|".join(map(re.escape, set(_OPERATORS) - _COMP_OPERATORS))})?
+                =(?!=)(?P<expr>.*)$
+            )|(?P<return>
+                (?!if|return|true|false|null|undefined|NaN)(?P<name>{_NAME_RE})$
+            )|(?P<indexing>
+                (?P<in>{_NAME_RE})\[(?P<idx>.+)\]$
+            )|(?P<attribute>
+                (?P<var>{_NAME_RE})(?:(?P<nullish>\?)?\.(?P<member>[^(]+)|\[(?P<member2>[^\]]+)\])\s*
+            )|(?P<function>
+                (?P<fname>{_NAME_RE})\((?P<args>.*)\)$
+            )''', expr)
+        if m and m.group('assign'):
+            left_val = local_vars.get(m.group('out'))
+
+            if not m.group('index'):
+                local_vars[m.group('out')] = self._operator(
+                    m.group('op'), left_val, m.group('expr'), expr, local_vars, allow_recursion)
+                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)
+
+            idx = self.interpret_expression(m.group('index'), local_vars, allow_recursion)
+            if not isinstance(idx, (int, float)):
+                raise self.Exception(f'List index {idx} must be integer', expr)
+            idx = int(idx)
+            left_val[idx] = self._operator(
+                m.group('op'), self._index(left_val, idx), m.group('expr'), expr, local_vars, allow_recursion)
+            return left_val[idx], should_return
+
+        elif expr.isdigit():
+            return int(expr), should_return
+
+        elif expr == 'break':
             raise JS_Break()
         elif expr == 'continue':
             raise JS_Continue()
+        elif expr == 'undefined':
+            return JS_Undefined, should_return
+        elif expr == 'NaN':
+            return float('NaN'), should_return
 
-        var_m = re.match(
-            r'(?!if|return|true|false|null)(?P<name>%s)$' % _NAME_RE,
-            expr)
-        if var_m:
-            return local_vars[var_m.group('name')]
+        elif m and m.group('return'):
+            return local_vars.get(m.group('name'), JS_Undefined), should_return
 
-        try:
-            return json.loads(expr)
-        except ValueError:
-            pass
+        with contextlib.suppress(ValueError):
+            return json.loads(js_to_json(expr, strict=True)), should_return
 
-        m = re.match(
-            r'(?P<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
-        if m:
+        if m and m.group('indexing'):
             val = local_vars[m.group('in')]
             idx = self.interpret_expression(m.group('idx'), local_vars, allow_recursion)
-            return val[idx]
+            return self._index(val, idx), should_return
 
-        for op, opfunc in _OPERATORS:
+        for op in _OPERATORS:
             separated = list(self._separate(expr, op))
-            if len(separated) < 2:
+            right_expr = separated.pop()
+            while True:
+                if op in '?<>*-' and len(separated) > 1 and not separated[-1].strip():
+                    separated.pop()
+                elif not (separated and op == '?' and right_expr.startswith('.')):
+                    break
+                right_expr = f'{op}{right_expr}'
+                if op != '-':
+                    right_expr = f'{separated.pop()}{op}{right_expr}'
+            if not separated:
                 continue
-            right_val = separated.pop()
-            left_val = op.join(separated)
-            left_val, should_abort = self.interpret_statement(
-                left_val, local_vars, allow_recursion - 1)
-            if should_abort:
-                raise ExtractorError(f'Premature left-side return of {op} in {expr!r}')
-            right_val, should_abort = self.interpret_statement(
-                right_val, local_vars, allow_recursion - 1)
-            if should_abort:
-                raise ExtractorError(f'Premature right-side return of {op} in {expr!r}')
-            return opfunc(left_val or 0, right_val)
+            left_val = self.interpret_expression(op.join(separated), local_vars, allow_recursion)
+            return self._operator(op, left_val, right_expr, expr, local_vars, allow_recursion), should_return
 
-        m = re.match(
-            r'(?P<var>%s)(?:\.(?P<member>[^(]+)|\[(?P<member2>[^]]+)\])\s*' % _NAME_RE,
-            expr)
-        if m:
-            variable = m.group('var')
-            member = remove_quotes(m.group('member') or m.group('member2'))
+        if m and m.group('attribute'):
+            variable, member, nullish = m.group('var', 'member', 'nullish')
+            if not member:
+                member = self.interpret_expression(m.group('member2'), local_vars, allow_recursion)
             arg_str = expr[m.end():]
             if arg_str.startswith('('):
-                arg_str, remaining = self._separate_at_paren(arg_str, ')')
+                arg_str, remaining = self._separate_at_paren(arg_str)
             else:
                 arg_str, remaining = None, arg_str
 
             def assertion(cndn, msg):
                 """ assert, but without risk of getting optimized out """
                 if not cndn:
-                    raise ExtractorError(f'{member} {msg}: {expr}')
+                    raise self.Exception(f'{member} {msg}', expr)
 
             def eval_method():
-                nonlocal member
-                if variable == 'String':
-                    obj = str
-                elif variable in local_vars:
-                    obj = local_vars[variable]
-                else:
+                if (variable, member) == ('console', 'debug'):
+                    if Debugger.ENABLED:
+                        Debugger.write(self.interpret_expression(f'[{arg_str}]', local_vars, allow_recursion))
+                    return
+
+                types = {
+                    'String': str,
+                    'Math': float,
+                }
+                obj = local_vars.get(variable, types.get(variable, NO_DEFAULT))
+                if obj is NO_DEFAULT:
                     if variable not in self._objects:
-                        self._objects[variable] = self.extract_object(variable)
-                    obj = self._objects[variable]
+                        try:
+                            self._objects[variable] = self.extract_object(variable)
+                        except self.Exception:
+                            if not nullish:
+                                raise
+                    obj = self._objects.get(variable, JS_Undefined)
+
+                if nullish and obj is JS_Undefined:
+                    return JS_Undefined
 
+                # Member access
                 if arg_str is None:
-                    # Member access
-                    if member == 'length':
-                        return len(obj)
-                    return obj[member]
+                    return self._index(obj, member, nullish)
 
                 # Function call
                 argvals = [
@@ -376,12 +671,17 @@ def eval_method():
                     if member == 'fromCharCode':
                         assertion(argvals, 'takes one or more arguments')
                         return ''.join(map(chr, argvals))
-                    raise ExtractorError(f'Unsupported string method {member}')
+                    raise self.Exception(f'Unsupported String method {member}', expr)
+                elif obj == float:
+                    if member == 'pow':
+                        assertion(len(argvals) == 2, 'takes two arguments')
+                        return argvals[0] ** argvals[1]
+                    raise self.Exception(f'Unsupported Math method {member}', expr)
 
                 if member == 'split':
                     assertion(argvals, 'takes one or more arguments')
-                    assertion(argvals == [''], 'with arguments is not implemented')
-                    return list(obj)
+                    assertion(len(argvals) == 1, 'with limit argument is not implemented')
+                    return obj.split(argvals[0]) if argvals[0] else list(obj)
                 elif member == 'join':
                     assertion(isinstance(obj, list), 'must be applied on a list')
                     assertion(len(argvals) == 1, 'takes exactly one argument')
@@ -427,7 +727,7 @@ def eval_method():
                     assertion(argvals, 'takes one or more arguments')
                     assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
                     f, this = (argvals + [''])[:2]
-                    return [f((item, idx, obj), this=this) for idx, item in enumerate(obj)]
+                    return [f((item, idx, obj), {'this': this}, allow_recursion) for idx, item in enumerate(obj)]
                 elif member == 'indexOf':
                     assertion(argvals, 'takes one or more arguments')
                     assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
@@ -436,72 +736,91 @@ def eval_method():
                         return obj.index(idx, start)
                     except ValueError:
                         return -1
+                elif member == 'charCodeAt':
+                    assertion(isinstance(obj, str), 'must be applied on a string')
+                    assertion(len(argvals) == 1, 'takes exactly one argument')
+                    idx = argvals[0] if isinstance(argvals[0], int) else 0
+                    if idx >= len(obj):
+                        return None
+                    return ord(obj[idx])
 
-                if isinstance(obj, list):
-                    member = int(member)
-                return obj[member](argvals)
+                idx = int(member) if isinstance(obj, list) else member
+                return obj[idx](argvals, allow_recursion=allow_recursion)
 
             if remaining:
-                return self.interpret_expression(
+                ret, should_abort = self.interpret_statement(
                     self._named_object(local_vars, eval_method()) + remaining,
                     local_vars, allow_recursion)
+                return ret, should_return or should_abort
             else:
-                return eval_method()
+                return eval_method(), should_return
 
-        m = re.match(r'^(?P<func>%s)\((?P<args>[a-zA-Z0-9_$,]*)\)$' % _NAME_RE, expr)
-        if m:
-            fname = m.group('func')
-            argvals = tuple(
-                int(v) if v.isdigit() else local_vars[v]
-                for v in self._separate(m.group('args')))
+        elif m and m.group('function'):
+            fname = m.group('fname')
+            argvals = [self.interpret_expression(v, local_vars, allow_recursion)
+                       for v in self._separate(m.group('args'))]
             if fname in local_vars:
-                return local_vars[fname](argvals)
+                return local_vars[fname](argvals, allow_recursion=allow_recursion), should_return
             elif fname not in self._functions:
                 self._functions[fname] = self.extract_function(fname)
-            return self._functions[fname](argvals)
+            return self._functions[fname](argvals, allow_recursion=allow_recursion), should_return
+
+        raise self.Exception(
+            f'Unsupported JS expression {truncate_string(expr, 20, 20) if expr != stmt else ""}', stmt)
 
-        if expr:
-            raise ExtractorError('Unsupported JS expression %r' % expr)
+    def interpret_expression(self, expr, local_vars, allow_recursion):
+        ret, should_return = self.interpret_statement(expr, local_vars, allow_recursion)
+        if should_return:
+            raise self.Exception('Cannot return from an expression', expr)
+        return ret
 
     def extract_object(self, objname):
         _FUNC_NAME_RE = r'''(?:[a-zA-Z$0-9]+|"[a-zA-Z$0-9]+"|'[a-zA-Z$0-9]+')'''
         obj = {}
         obj_m = re.search(
             r'''(?x)
-                (?<!this\.)%s\s*=\s*{\s*
+                (?<!\.)%s\s*=\s*{\s*
                     (?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
                 }\s*;
             ''' % (re.escape(objname), _FUNC_NAME_RE),
             self.code)
+        if not obj_m:
+            raise self.Exception(f'Could not find object {objname}')
         fields = obj_m.group('fields')
         # Currently, it only supports function definitions
         fields_m = re.finditer(
             r'''(?x)
-                (?P<key>%s)\s*:\s*function\s*\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}
-            ''' % _FUNC_NAME_RE,
+                (?P<key>%s)\s*:\s*function\s*\((?P<args>(?:%s|,)*)\){(?P<code>[^}]+)}
+            ''' % (_FUNC_NAME_RE, _NAME_RE),
             fields)
         for f in fields_m:
             argnames = f.group('args').split(',')
-            obj[remove_quotes(f.group('key'))] = self.build_function(argnames, f.group('code'))
+            name = remove_quotes(f.group('key'))
+            obj[name] = function_with_repr(self.build_function(argnames, f.group('code')), f'F<{name}>')
 
         return obj
 
     def extract_function_code(self, funcname):
         """ @returns argnames, code """
         func_m = re.search(
-            r'''(?x)
-                (?:function\s+%s|[{;,]\s*%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
+            r'''(?xs)
+                (?:
+                    function\s+%(name)s|
+                    [{;,]\s*%(name)s\s*=\s*function|
+                    (?:var|const|let)\s+%(name)s\s*=\s*function
+                )\s*
                 \((?P<args>[^)]*)\)\s*
-                (?P<code>\{(?:(?!};)[^"]|"([^"]|\\")*")+\})''' % (
-                re.escape(funcname), re.escape(funcname), re.escape(funcname)),
+                (?P<code>{.+})''' % {'name': re.escape(funcname)},
             self.code)
-        code, _ = self._separate_at_paren(func_m.group('code'), '}')  # refine the match
         if func_m is None:
-            raise ExtractorError('Could not find JS function %r' % funcname)
-        return func_m.group('args').split(','), code
+            raise self.Exception(f'Could not find JS function "{funcname}"')
+        code, _ = self._separate_at_paren(func_m.group('code'))
+        return [x.strip() for x in func_m.group('args').split(',')], code
 
     def extract_function(self, funcname):
-        return self.extract_function_from_code(*self.extract_function_code(funcname))
+        return function_with_repr(
+            self.extract_function_from_code(*self.extract_function_code(funcname)),
+            f'F<{funcname}>')
 
     def extract_function_from_code(self, argnames, code, *global_stack):
         local_vars = {}
@@ -510,12 +829,10 @@ def extract_function_from_code(self, argnames, code, *global_stack):
             if mobj is None:
                 break
             start, body_start = mobj.span()
-            body, remaining = self._separate_at_paren(code[body_start - 1:], '}')
-            name = self._named_object(
-                local_vars,
-                self.extract_function_from_code(
-                    [str.strip(x) for x in mobj.group('args').split(',')],
-                    body, local_vars, *global_stack))
+            body, remaining = self._separate_at_paren(code[body_start - 1:])
+            name = self._named_object(local_vars, self.extract_function_from_code(
+                [x.strip() for x in mobj.group('args').split(',')],
+                body, local_vars, *global_stack))
             code = code[:start] + name + remaining
         return self.build_function(argnames, code, local_vars, *global_stack)
 
@@ -524,17 +841,13 @@ def call_function(self, funcname, *args):
 
     def build_function(self, argnames, code, *global_stack):
         global_stack = list(global_stack) or [{}]
-        local_vars = global_stack.pop(0)
-
-        def resf(args, **kwargs):
-            local_vars.update({
-                **dict(zip(argnames, args)),
-                **kwargs
-            })
-            var_stack = LocalNameSpace(local_vars, *global_stack)
-            for stmt in self._separate(code.replace('\n', ''), ';'):
-                ret, should_abort = self.interpret_statement(stmt, var_stack)
-                if should_abort:
-                    break
-            return ret
+        argnames = tuple(argnames)
+
+        def resf(args, kwargs={}, allow_recursion=100):
+            global_stack[0].update(itertools.zip_longest(argnames, args, fillvalue=None))
+            global_stack[0].update(kwargs)
+            var_stack = LocalNameSpace(*global_stack)
+            ret, should_abort = self.interpret_statement(code.replace('\n', ' '), var_stack, allow_recursion - 1)
+            if should_abort:
+                return ret
         return resf