Source code for apache_beam.typehints.trivial_inference

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"""Trivial type inference for simple functions.

For internal use only; no backwards-compatibility guarantees.
from __future__ import absolute_import
from __future__ import print_function

import collections
import dis
import inspect
import pprint
import sys
import traceback
import types
from builtins import object
from builtins import zip
from functools import reduce

from apache_beam.typehints import Any
from apache_beam.typehints import typehints

# pylint: disable=wrong-import-order, wrong-import-position, ungrouped-imports
try:                  # Python 2
  import __builtin__ as builtins
except ImportError:   # Python 3
  import builtins
# pylint: enable=wrong-import-order, wrong-import-position, ungrouped-imports

[docs]class TypeInferenceError(ValueError): """Error to raise when type inference failed.""" pass
[docs]def instance_to_type(o): """Given a Python object o, return the corresponding type hint. """ t = type(o) if o is None: return type(None) elif t not in typehints.DISALLOWED_PRIMITIVE_TYPES: # pylint: disable=deprecated-types-field if sys.version_info[0] == 2 and t == types.InstanceType: return o.__class__ if t == BoundMethod: return types.MethodType return t elif t == tuple: return typehints.Tuple[[instance_to_type(item) for item in o]] elif t == list: return typehints.List[ typehints.Union[[instance_to_type(item) for item in o]] ] elif t == set: return typehints.Set[ typehints.Union[[instance_to_type(item) for item in o]] ] elif t == dict: return typehints.Dict[ typehints.Union[[instance_to_type(k) for k, v in o.items()]], typehints.Union[[instance_to_type(v) for k, v in o.items()]], ] else: raise TypeInferenceError('Unknown forbidden type: %s' % t)
[docs]def union_list(xs, ys): assert len(xs) == len(ys) return [union(x, y) for x, y in zip(xs, ys)]
[docs]class Const(object): def __init__(self, value): self.value = value self.type = instance_to_type(value) def __eq__(self, other): return isinstance(other, Const) and self.value == other.value def __ne__(self, other): # TODO(BEAM-5949): Needed for Python 2 compatibility. return not self == other def __hash__(self): return hash(self.value) def __repr__(self): return 'Const[%s]' % str(self.value)[:100]
[docs] @staticmethod def unwrap(x): if isinstance(x, Const): return x.type return x
[docs] @staticmethod def unwrap_all(xs): return [Const.unwrap(x) for x in xs]
[docs]class FrameState(object): """Stores the state of the frame at a particular point of execution. """ def __init__(self, f, local_vars=None, stack=()): self.f = f = f.__code__ self.vars = list(local_vars) self.stack = list(stack) def __eq__(self, other): return isinstance(other, FrameState) and self.__dict__ == other.__dict__ def __ne__(self, other): # TODO(BEAM-5949): Needed for Python 2 compatibility. return not self == other def __hash__(self): return hash(tuple(sorted(self.__dict__.items())))
[docs] def copy(self): return FrameState(self.f, self.vars, self.stack)
[docs] def const_type(self, i): return Const([i])
[docs] def get_closure(self, i): num_cellvars = len( if i < num_cellvars: return self.vars[i] else: return self.f.__closure__[i - num_cellvars].cell_contents
[docs] def closure_type(self, i): """Returns a TypeConstraint or Const.""" val = self.get_closure(i) if isinstance(val, typehints.TypeConstraint): return val else: return Const(val)
[docs] def get_global(self, i): name = self.get_name(i) if name in self.f.__globals__: return Const(self.f.__globals__[name]) if name in builtins.__dict__: return Const(builtins.__dict__[name]) return Any
[docs] def get_name(self, i): return[i]
def __repr__(self): return 'Stack: %s Vars: %s' % (self.stack, self.vars) def __or__(self, other): if self is None: return other.copy() elif other is None: return self.copy() return FrameState(self.f, union_list(self.vars, other.vars), union_list( self.stack, other.stack)) def __ror__(self, left): return self | left
[docs]def union(a, b): """Returns the union of two types or Const values. """ if a == b: return a elif not a: return b elif not b: return a a = Const.unwrap(a) b = Const.unwrap(b) # TODO(robertwb): Work this into the Union code in a more generic way. if type(a) == type(b) and element_type(a) == typehints.Union[()]: return b elif type(a) == type(b) and element_type(b) == typehints.Union[()]: return a return typehints.Union[a, b]
[docs]def finalize_hints(type_hint): """Sets type hint for empty data structures to Any.""" def visitor(tc, unused_arg): if isinstance(tc, typehints.DictConstraint): empty_union = typehints.Union[()] if tc.key_type == empty_union: tc.key_type = Any if tc.value_type == empty_union: tc.value_type = Any if isinstance(type_hint, typehints.TypeConstraint): type_hint.visit(visitor, None)
[docs]def element_type(hint): """Returns the element type of a composite type. """ hint = Const.unwrap(hint) if isinstance(hint, typehints.SequenceTypeConstraint): return hint.inner_type elif isinstance(hint, typehints.TupleHint.TupleConstraint): return typehints.Union[hint.tuple_types] return Any
[docs]def key_value_types(kv_type): """Returns the key and value type of a KV type. """ # TODO(robertwb): Unions of tuples, etc. # TODO(robertwb): Assert? if (isinstance(kv_type, typehints.TupleHint.TupleConstraint) and len(kv_type.tuple_types) == 2): return kv_type.tuple_types return Any, Any
known_return_types = {len: int, hash: int,}
[docs]class BoundMethod(object): """Used to create a bound method when we only know the type of the instance. """ def __init__(self, func, type): """Instantiates a bound method object. Args: func (types.FunctionType): The method's underlying function type (type): The class of the method. """ self.func = func self.type = type
[docs]def hashable(c): try: hash(c) return True except TypeError: return False
[docs]def infer_return_type(c, input_types, debug=False, depth=5): """Analyses a callable to deduce its return type. Args: c: A Python callable to infer the return type of. input_types: A sequence of inputs corresponding to the input types. debug: Whether to print verbose debugging information. depth: Maximum inspection depth during type inference. Returns: A TypeConstraint that that the return value of this function will (likely) satisfy given the specified inputs. """ try: if hashable(c) and c in known_return_types: return known_return_types[c] elif isinstance(c, types.FunctionType): return infer_return_type_func(c, input_types, debug, depth) elif isinstance(c, types.MethodType): if c.__self__ is not None: input_types = [Const(c.__self__)] + input_types return infer_return_type_func(c.__func__, input_types, debug, depth) elif isinstance(c, BoundMethod): input_types = [c.type] + input_types return infer_return_type_func(c.func, input_types, debug, depth) elif inspect.isclass(c): if c in typehints.DISALLOWED_PRIMITIVE_TYPES: return { list: typehints.List[Any], set: typehints.Set[Any], tuple: typehints.Tuple[Any, ...], dict: typehints.Dict[Any, Any] }[c] return c else: return Any except TypeInferenceError: if debug: traceback.print_exc() return Any except Exception: if debug: sys.stdout.flush() raise else: return Any
[docs]def infer_return_type_func(f, input_types, debug=False, depth=0): """Analyses a function to deduce its return type. Args: f: A Python function object to infer the return type of. input_types: A sequence of inputs corresponding to the input types. debug: Whether to print verbose debugging information. depth: Maximum inspection depth during type inference. Returns: A TypeConstraint that that the return value of this function will (likely) satisfy given the specified inputs. Raises: TypeInferenceError: if no type can be inferred. """ if debug: print() print(f, id(f), input_types) dis.dis(f) from . import opcodes simple_ops = dict((k.upper(), v) for k, v in opcodes.__dict__.items()) co = f.__code__ code = co.co_code end = len(code) pc = 0 extended_arg = 0 # Python 2 only. free = None yields = set() returns = set() # TODO(robertwb): Default args via inspect module. local_vars = list(input_types) + [typehints.Union[()]] * (len(co.co_varnames) - len(input_types)) state = FrameState(f, local_vars) states = collections.defaultdict(lambda: None) jumps = collections.defaultdict(int) # In Python 3, use dis library functions to disassemble bytecode and handle # EXTENDED_ARGs. is_py3 = sys.version_info[0] == 3 if is_py3: ofs_table = {} # offset -> instruction for instruction in dis.get_instructions(f): ofs_table[instruction.offset] = instruction # Python 2 - 3.5: 1 byte opcode + optional 2 byte arg (1 or 3 bytes). # Python 3.6+: 1 byte opcode + 1 byte arg (2 bytes, arg may be ignored). if sys.version_info >= (3, 6): inst_size = 2 opt_arg_size = 0 else: inst_size = 1 opt_arg_size = 2 last_pc = -1 while pc < end: # pylint: disable=too-many-nested-blocks start = pc if is_py3: instruction = ofs_table[pc] op = instruction.opcode else: op = ord(code[pc]) if debug: print('-->' if pc == last_pc else ' ', end=' ') print(repr(pc).rjust(4), end=' ') print(dis.opname[op].ljust(20), end=' ') pc += inst_size if op >= dis.HAVE_ARGUMENT: if is_py3: arg = instruction.arg else: arg = ord(code[pc]) + ord(code[pc + 1]) * 256 + extended_arg extended_arg = 0 pc += opt_arg_size if op == dis.EXTENDED_ARG: extended_arg = arg * 65536 if debug: print(str(arg).rjust(5), end=' ') if op in dis.hasconst: print('(' + repr(co.co_consts[arg]) + ')', end=' ') elif op in dis.hasname: print('(' + co.co_names[arg] + ')', end=' ') elif op in dis.hasjrel: print('(to ' + repr(pc + arg) + ')', end=' ') elif op in dis.haslocal: print('(' + co.co_varnames[arg] + ')', end=' ') elif op in dis.hascompare: print('(' + dis.cmp_op[arg] + ')', end=' ') elif op in dis.hasfree: if free is None: free = co.co_cellvars + co.co_freevars print('(' + free[arg] + ')', end=' ') # Actually emulate the op. if state is None and states[start] is None: # No control reaches here (yet). if debug: print() continue state |= states[start] opname = dis.opname[op] jmp = jmp_state = None if opname.startswith('CALL_FUNCTION'): if sys.version_info < (3, 6): # Each keyword takes up two arguments on the stack (name and value). standard_args = (arg & 0xFF) + 2 * (arg >> 8) var_args = 'VAR' in opname kw_args = 'KW' in opname pop_count = standard_args + var_args + kw_args + 1 if depth <= 0: return_type = Any elif arg >> 8: # TODO(robertwb): Handle this case. return_type = Any elif isinstance(state.stack[-pop_count], Const): # TODO(robertwb): Handle this better. if var_args or kw_args: state.stack[-1] = Any state.stack[-var_args - kw_args] = Any return_type = infer_return_type(state.stack[-pop_count].value, state.stack[1 - pop_count:], debug=debug, depth=depth - 1) else: return_type = Any state.stack[-pop_count:] = [return_type] else: # Python 3.6+ if opname == 'CALL_FUNCTION': pop_count = arg + 1 if depth <= 0: return_type = Any else: return_type = infer_return_type(state.stack[-pop_count].value, state.stack[1 - pop_count:], debug=debug, depth=depth - 1) elif opname == 'CALL_FUNCTION_KW': # TODO(udim): Handle keyword arguments. Requires passing them by name # to infer_return_type. pop_count = arg + 2 return_type = Any elif opname == 'CALL_FUNCTION_EX': # stack[-has_kwargs]: Map of keyword args. # stack[-1 - has_kwargs]: Iterable of positional args. # stack[-2 - has_kwargs]: Function to call. has_kwargs = arg & 1 # type: int pop_count = has_kwargs + 2 if has_kwargs: # TODO(udim): Unimplemented. Requires same functionality as a # CALL_FUNCTION_KW implementation. return_type = Any else: args = state.stack[-1] _callable = state.stack[-2] if isinstance(args, typehints.ListConstraint): # Case where there's a single var_arg argument. args = [args] elif isinstance(args, typehints.TupleConstraint): args = list(args._inner_types()) return_type = infer_return_type(_callable.value, args, debug=debug, depth=depth - 1) else: raise TypeInferenceError('unable to handle %s' % opname) state.stack[-pop_count:] = [return_type] elif opname == 'CALL_METHOD': pop_count = 1 + arg # LOAD_METHOD will return a non-Const (Any) if loading from an Any. if isinstance(state.stack[-pop_count], Const) and depth > 0: return_type = infer_return_type(state.stack[-pop_count].value, state.stack[1 - pop_count:], debug=debug, depth=depth - 1) else: return_type = typehints.Any state.stack[-pop_count:] = [return_type] elif opname in simple_ops: if debug: print("Executing simple op " + opname) simple_ops[opname](state, arg) elif opname == 'RETURN_VALUE': returns.add(state.stack[-1]) state = None elif opname == 'YIELD_VALUE': yields.add(state.stack[-1]) elif opname == 'JUMP_FORWARD': jmp = pc + arg jmp_state = state state = None elif opname == 'JUMP_ABSOLUTE': jmp = arg jmp_state = state state = None elif opname in ('POP_JUMP_IF_TRUE', 'POP_JUMP_IF_FALSE'): state.stack.pop() jmp = arg jmp_state = state.copy() elif opname in ('JUMP_IF_TRUE_OR_POP', 'JUMP_IF_FALSE_OR_POP'): jmp = arg jmp_state = state.copy() state.stack.pop() elif opname == 'FOR_ITER': jmp = pc + arg jmp_state = state.copy() jmp_state.stack.pop() state.stack.append(element_type(state.stack[-1])) else: raise TypeInferenceError('unable to handle %s' % opname) if jmp is not None: # TODO(robertwb): Is this guaranteed to converge? new_state = states[jmp] | jmp_state if jmp < pc and new_state != states[jmp] and jumps[pc] < 5: jumps[pc] += 1 pc = jmp states[jmp] = new_state if debug: print() print(state) pprint.pprint(dict(item for item in states.items() if item[1])) if yields: result = typehints.Iterable[reduce(union, Const.unwrap_all(yields))] else: result = reduce(union, Const.unwrap_all(returns)) finalize_hints(result) if debug: print(f, id(f), input_types, '->', result) return result