yt-dlp/yt_dlp/jsinterp.py

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import json
import operator
import re
from collections.abc import MutableMapping
from .utils import ExtractorError, remove_quotes
_OPERATORS = [
('|', operator.or_),
('^', operator.xor),
('&', operator.and_),
('>>', operator.rshift),
('<<', operator.lshift),
('-', operator.sub),
('+', operator.add),
('%', operator.mod),
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('/', 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]*'
_MATCHING_PARENS = dict(zip('({[', ')}]'))
class JS_Break(ExtractorError):
def __init__(self):
ExtractorError.__init__(self, 'Invalid break')
class JS_Continue(ExtractorError):
def __init__(self):
ExtractorError.__init__(self, 'Invalid continue')
class LocalNameSpace(MutableMapping):
def __init__(self, *stack):
self.stack = tuple(stack)
def __getitem__(self, key):
for scope in self.stack:
if key in scope:
return scope[key]
raise KeyError(key)
def __setitem__(self, key, value):
for scope in self.stack:
if key in scope:
scope[key] = value
break
else:
self.stack[0][key] = value
return 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))
def __repr__(self):
return f'LocalNameSpace{self.stack}'
class JSInterpreter:
def __init__(self, code, objects=None):
if objects is None:
objects = {}
self.code = code
self._functions = {}
self._objects = objects
self.__named_object_counter = 0
def _named_object(self, namespace, obj):
self.__named_object_counter += 1
name = f'__yt_dlp_jsinterp_obj{self.__named_object_counter}'
namespace[name] = obj
return name
@staticmethod
def _separate(expr, delim=',', max_split=None):
if not expr:
return
counters = {k: 0 for k in _MATCHING_PARENS.values()}
start, splits, pos, delim_len = 0, 0, 0, len(delim) - 1
for idx, char in enumerate(expr):
if char in _MATCHING_PARENS:
counters[_MATCHING_PARENS[char]] += 1
elif char in counters:
counters[char] -= 1
if char != delim[pos] or any(counters.values()):
pos = 0
continue
elif pos != delim_len:
pos += 1
continue
yield expr[start: idx - delim_len]
start, pos = idx + 1, 0
splits += 1
if max_split and splits >= max_split:
break
yield expr[start:]
@staticmethod
def _separate_at_paren(expr, delim):
separated = list(JSInterpreter._separate(expr, delim, 1))
if len(separated) < 2:
raise ExtractorError(f'No terminating paren {delim} in {expr}')
return separated[0][1:].strip(), separated[1].strip()
def interpret_statement(self, stmt, local_vars, allow_recursion=100):
if allow_recursion < 0:
raise ExtractorError('Recursion limit reached')
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
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
else:
# Try interpreting it as an expression
expr = stmt
v = self.interpret_expression(expr, local_vars, allow_recursion)
return v, should_abort
def interpret_expression(self, expr, local_vars, allow_recursion):
expr = expr.strip()
if expr == '': # Empty expression
return None
if expr.startswith('{'):
inner, outer = self._separate_at_paren(expr, '}')
inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion - 1)
if not outer or should_abort:
return inner
else:
expr = json.dumps(inner) + 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
else:
expr = json.dumps(inner) + outer
if expr.startswith('['):
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)
if should_abort:
return ret
return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
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]
m = re.match(r'for\s*\(', expr)
if m:
constructor, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
if remaining.startswith('{'):
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:], ')')
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}')
while True:
if not self.interpret_expression(cndn, local_vars, allow_recursion):
break
try:
ret, should_abort = self.interpret_statement(body, local_vars, allow_recursion - 1)
if should_abort:
return ret
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]
m = re.match(r'switch\s*\(', expr)
if m:
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:]
for default in (False, True):
matched = False
for item in items:
case, stmt = (i.strip() for i in self._separate(item, ':', 1))
if default:
matched = matched or case == 'default'
elif not matched:
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)
if should_abort:
return ret
except JS_Break:
break
if matched:
break
return self.interpret_statement(expr, local_vars, allow_recursion - 1)[0]
# 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)
for m in re.finditer(rf'''(?x)
(?P<pre_sign>\+\+|--)(?P<var1>{_NAME_RE})|
(?P<var2>{_NAME_RE})(?P<post_sign>\+\+|--)''', expr):
var = m.group('var1') or m.group('var2')
start, end = m.span()
sign = m.group('pre_sign') or m.group('post_sign')
ret = local_vars[var]
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>.*)$''', expr)
if not m:
continue
right_val = self.interpret_expression(m.group('expr'), local_vars, allow_recursion)
if m.groupdict().get('index'):
lvar = local_vars[m.group('out')]
idx = self.interpret_expression(m.group('index'), local_vars, allow_recursion)
if not isinstance(idx, int):
raise ExtractorError(f'List indices must be integers: {idx}')
cur = lvar[idx]
val = opfunc(cur, right_val)
lvar[idx] = val
return val
else:
cur = local_vars.get(m.group('out'))
val = opfunc(cur, right_val)
local_vars[m.group('out')] = val
return val
if expr.isdigit():
return int(expr)
if expr == 'break':
raise JS_Break()
elif expr == 'continue':
raise JS_Continue()
var_m = re.match(
r'(?!if|return|true|false|null)(?P<name>%s)$' % _NAME_RE,
expr)
if var_m:
return local_vars[var_m.group('name')]
try:
return json.loads(expr)
except ValueError:
pass
m = re.match(
r'(?P<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
if m:
val = local_vars[m.group('in')]
idx = self.interpret_expression(m.group('idx'), local_vars, allow_recursion)
return val[idx]
for op, opfunc in _OPERATORS:
separated = list(self._separate(expr, op))
if len(separated) < 2:
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)
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'))
arg_str = expr[m.end():]
if arg_str.startswith('('):
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}')
def eval_method():
nonlocal member
if variable == 'String':
obj = str
elif variable in local_vars:
obj = local_vars[variable]
else:
if variable not in self._objects:
self._objects[variable] = self.extract_object(variable)
obj = self._objects[variable]
if arg_str is None:
# Member access
if member == 'length':
return len(obj)
return obj[member]
# Function call
argvals = [
self.interpret_expression(v, local_vars, allow_recursion)
for v in self._separate(arg_str)]
if obj == str:
if member == 'fromCharCode':
assertion(argvals, 'takes one or more arguments')
return ''.join(map(chr, argvals))
raise ExtractorError(f'Unsupported string method {member}')
if member == 'split':
assertion(argvals, 'takes one or more arguments')
assertion(argvals == [''], 'with arguments is not implemented')
return list(obj)
elif member == 'join':
assertion(isinstance(obj, list), 'must be applied on a list')
assertion(len(argvals) == 1, 'takes exactly one argument')
return argvals[0].join(obj)
elif member == 'reverse':
assertion(not argvals, 'does not take any arguments')
obj.reverse()
return obj
elif member == 'slice':
assertion(isinstance(obj, list), 'must be applied on a list')
assertion(len(argvals) == 1, 'takes exactly one argument')
return obj[argvals[0]:]
elif member == 'splice':
assertion(isinstance(obj, list), 'must be applied on a list')
assertion(argvals, 'takes one or more arguments')
index, howMany = map(int, (argvals + [len(obj)])[:2])
if index < 0:
index += len(obj)
add_items = argvals[2:]
res = []
for i in range(index, min(index + howMany, len(obj))):
res.append(obj.pop(index))
for i, item in enumerate(add_items):
obj.insert(index + i, item)
return res
elif member == 'unshift':
assertion(isinstance(obj, list), 'must be applied on a list')
assertion(argvals, 'takes one or more arguments')
for item in reversed(argvals):
obj.insert(0, item)
return obj
elif member == 'pop':
assertion(isinstance(obj, list), 'must be applied on a list')
assertion(not argvals, 'does not take any arguments')
if not obj:
return
return obj.pop()
elif member == 'push':
assertion(argvals, 'takes one or more arguments')
obj.extend(argvals)
return obj
elif member == 'forEach':
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)]
elif member == 'indexOf':
assertion(argvals, 'takes one or more arguments')
assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
idx, start = (argvals + [0])[:2]
try:
return obj.index(idx, start)
except ValueError:
return -1
if isinstance(obj, list):
member = int(member)
return obj[member](argvals)
if remaining:
return self.interpret_expression(
self._named_object(local_vars, eval_method()) + remaining,
local_vars, allow_recursion)
else:
return eval_method()
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')))
if fname in local_vars:
return local_vars[fname](argvals)
elif fname not in self._functions:
self._functions[fname] = self.extract_function(fname)
return self._functions[fname](argvals)
if expr:
raise ExtractorError('Unsupported JS expression %r' % expr)
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*
(?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
}\s*;
''' % (re.escape(objname), _FUNC_NAME_RE),
self.code)
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,
fields)
for f in fields_m:
argnames = f.group('args').split(',')
obj[remove_quotes(f.group('key'))] = self.build_function(argnames, f.group('code'))
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*
\((?P<args>[^)]*)\)\s*
(?P<code>\{(?:(?!};)[^"]|"([^"]|\\")*")+\})''' % (
re.escape(funcname), re.escape(funcname), re.escape(funcname)),
self.code)
code, _ = self._separate_at_paren(func_m.group('code'), '}') # refine the match
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if func_m is None:
raise ExtractorError('Could not find JS function %r' % funcname)
return func_m.group('args').split(','), code
def extract_function(self, funcname):
return self.extract_function_from_code(*self.extract_function_code(funcname))
def extract_function_from_code(self, argnames, code, *global_stack):
local_vars = {}
while True:
mobj = re.search(r'function\((?P<args>[^)]*)\)\s*{', code)
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))
code = code[:start] + name + remaining
return self.build_function(argnames, code, local_vars, *global_stack)
def call_function(self, funcname, *args):
return self.extract_function(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
return resf