yt-dlp/yt_dlp/jsinterp.py

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import collections
import contextlib
import itertools
import json
import math
import operator
import re
from .utils import (
NO_DEFAULT,
ExtractorError,
js_to_json,
remove_quotes,
truncate_string,
unified_timestamp,
write_string,
)
_NAME_RE = r'[a-zA-Z_$][\w$]*'
# Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
_OPERATORS = { # None => Defined in JSInterpreter._operator
'?': None,
'||': None,
'&&': None,
'&': operator.and_,
'|': operator.or_,
'^': operator.xor,
'===': operator.is_,
'!==': operator.is_not,
'==': operator.eq,
'!=': operator.ne,
'<=': lambda a, b: (a or 0) <= (b or 0),
'>=': lambda a, b: (a or 0) >= (b or 0),
'<': lambda a, b: (a or 0) < (b or 0),
'>': lambda a, b: (a or 0) > (b or 0),
'>>': operator.rshift,
'<<': operator.lshift,
'+': lambda a, b: (a or 0) + (b or 0),
'-': lambda a, b: (a or 0) - (b or 0),
'*': lambda a, b: (a or 0) * (b or 0),
'/': lambda a, b: (a or 0) / b,
'%': operator.mod,
'**': operator.pow,
}
_COMP_OPERATORS = {'===', '!==', '==', '!=', '<=', '>=', '<', '>'}
_MATCHING_PARENS = dict(zip('({[', ')}]'))
_QUOTES = '\'"'
def _ternary(cndn, if_true=True, if_false=False):
"""Simulate JS's ternary operator (cndn?if_true:if_false)"""
if cndn in (False, None, 0, ''):
return if_false
with contextlib.suppress(TypeError):
if math.isnan(cndn): # NB: NaN cannot be checked by membership
return if_false
return if_true
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(collections.ChainMap):
def __setitem__(self, key, value):
for scope in self.maps:
if key in scope:
scope[key] = value
return
self.maps[0][key] = value
def __delitem__(self, key):
raise NotImplementedError('Deleting is not supported')
class Debugger:
import sys
ENABLED = False and 'pytest' in sys.modules
@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)
ret, should_ret = f(self, stmt, local_vars, allow_recursion, *args, **kwargs)
if cls.ENABLED and stmt.strip():
cls.write(['->', '=>'][should_ret], repr(ret), '<-|', stmt, level=allow_recursion)
return ret, should_ret
return interpret_statement
class JSInterpreter:
__named_object_counter = 0
def __init__(self, code, objects=None):
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}'
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
in_quote, escaping = None, False
for idx, char in enumerate(expr):
if not in_quote and char in _MATCHING_PARENS:
counters[_MATCHING_PARENS[char]] += 1
elif not in_quote and char in counters:
counters[char] -= 1
elif not escaping and char in _QUOTES and in_quote in (char, None):
in_quote = None if in_quote else char
escaping = not escaping and in_quote and char == '\\'
if char != delim[pos] or any(counters.values()) or in_quote:
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:]
@classmethod
def _separate_at_paren(cls, expr, delim):
separated = list(cls._separate(expr, delim, 1))
if len(separated) < 2:
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 == '&&') ^ _ternary(left_val):
return left_val # short circuiting
elif op == '?':
right_expr = _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):
if idx == 'length':
return len(obj)
try:
return obj[int(idx)] if isinstance(obj, list) else obj[idx]
except Exception as e:
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 self.Exception('Recursion limit reached')
allow_recursion -= 1
should_return = False
sub_statements = list(self._separate(stmt, ';')) or ['']
expr = stmt = sub_statements.pop().strip()
for sub_stmt in sub_statements:
ret, should_return = self.interpret_statement(sub_stmt, local_vars, allow_recursion)
if should_return:
return ret, should_return
m = re.match(r'(?P<var>(?:var|const|let)\s)|return(?:\s+|$)', stmt)
if m:
expr = stmt[len(m.group(0)):].strip()
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)
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:], ')')
expr = unified_timestamp(
self.interpret_expression(left, local_vars, allow_recursion), False)
if not expr:
raise self.Exception(f'Failed to parse date {left!r}', expr)
expr = self._dump(int(expr * 1000), local_vars) + right
else:
raise self.Exception(f'Unsupported object {obj}', expr)
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)
if not outer or should_abort:
return inner, should_abort or should_return
else:
expr = self._dump(inner, local_vars) + outer
if expr.startswith('('):
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 = self._dump(inner, local_vars) + 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'(?P<try>try|finally)\s*|(?:(?P<catch>catch)|(?P<for>for)|(?P<switch>switch))\s*\(', expr)
if m and m.group('try'):
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)
if should_abort:
return ret, True
ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
return ret, should_abort or should_return
elif m and m.group('catch'):
# We ignore the catch block
_, expr = self._separate_at_paren(expr, '}')
ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
return ret, should_abort or should_return
elif m and m.group('for'):
constructor, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
if remaining.startswith('{'):
body, expr = self._separate_at_paren(remaining, '}')
else:
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, ';')
self.interpret_expression(start, local_vars, allow_recursion)
while True:
if not _ternary(self.interpret_expression(cndn, local_vars, allow_recursion)):
break
try:
ret, should_abort = self.interpret_statement(body, local_vars, allow_recursion)
if should_abort:
return ret, True
except JS_Break:
break
except JS_Continue:
pass
self.interpret_expression(increment, local_vars, allow_recursion)
ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
return ret, should_abort or should_return
elif m and m.group('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:]
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)
if should_abort:
return ret
except JS_Break:
break
if matched:
break
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))
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})|
(?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] + self._dump(ret, local_vars) + expr[end:]
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)(?P<name>{_NAME_RE})$
)|(?P<indexing>
(?P<in>{_NAME_RE})\[(?P<idx>.+)\]$
)|(?P<attribute>
(?P<var>{_NAME_RE})(?:\.(?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 is None:
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'), 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 m and m.group('return'):
return local_vars[m.group('name')], should_return
with contextlib.suppress(ValueError):
return json.loads(js_to_json(expr, strict=True)), should_return
if m and m.group('indexing'):
val = local_vars[m.group('in')]
idx = self.interpret_expression(m.group('idx'), local_vars, allow_recursion)
return self._index(val, idx), should_return
for op in _OPERATORS:
separated = list(self._separate(expr, op))
right_expr = separated.pop()
while op in '<>*-' and len(separated) > 1 and not separated[-1].strip():
separated.pop()
right_expr = f'{op}{right_expr}'
if op != '-':
right_expr = f'{separated.pop()}{op}{right_expr}'
if not separated:
continue
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
if m and m.group('attribute'):
variable = m.group('var')
member = m.group('member')
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, ')')
else:
arg_str, remaining = None, arg_str
def assertion(cndn, msg):
""" assert, but without risk of getting optimized out """
if not cndn:
raise self.Exception(f'{member} {msg}', expr)
def eval_method():
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]
# Member access
if arg_str is None:
return self._index(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 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(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')
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}, 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')
idx, start = (argvals + [0])[:2]
try:
return obj.index(idx, start)
except ValueError:
return -1
idx = int(member) if isinstance(obj, list) else member
return obj[idx](argvals, allow_recursion=allow_recursion)
if remaining:
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(), should_return
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, allow_recursion=allow_recursion), should_return
elif fname not in self._functions:
self._functions[fname] = self.extract_function(fname)
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)
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*
(?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*\((?P<args>(?:%s|,)*)\){(?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'))
return obj
def extract_function_code(self, funcname):
""" @returns argnames, code """
func_m = re.search(
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>{.+})''' % {'name': re.escape(funcname)},
self.code)
code, _ = self._separate_at_paren(func_m.group('code'), '}')
2014-03-30 07:15:14 +02:00
if func_m is None:
raise self.Exception(f'Could not find JS function "{funcname}"')
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))
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(
[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)
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 [{}]
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