#
# Licensed to the Apache Software Foundation (ASF) under one or more
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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Trivial type inference for simple functions.
For internal use only; no backwards-compatibility guarantees.
"""
import __builtin__
import collections
import dis
import pprint
import sys
import types
from apache_beam.typehints import Any
from apache_beam.typehints import typehints
[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:
# TODO(robertwb): Eliminate inconsistent use of None vs. NoneType.
return None
elif t not in typehints.DISALLOWED_PRIMITIVE_TYPES:
if t == types.InstanceType:
return o.__class__
elif 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 __hash__(self):
return hash(self.value)
def __repr__(self):
return 'Const[%s]' % str(self.value)[:100]
@staticmethod
[docs] def unwrap(x):
if isinstance(x, Const):
return x.type
return x
@staticmethod
[docs] 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
self.co = f.func_code
self.vars = list(local_vars)
self.stack = list(stack)
def __eq__(self, other):
return self.__dict__ == other.__dict__
[docs] def copy(self):
return FrameState(self.f, self.vars, self.stack)
[docs] def const_type(self, i):
return Const(self.co.co_consts[i])
[docs] def closure_type(self, i):
ncellvars = len(self.co.co_cellvars)
if i < ncellvars:
return Any
return Const(self.f.func_closure[i - ncellvars].cell_contents)
[docs] def get_global(self, i):
name = self.get_name(i)
if name in self.f.func_globals:
return Const(self.f.func_globals[name])
if name in __builtin__.__dict__:
return Const(__builtin__.__dict__[name])
return Any
[docs] def get_name(self, i):
return self.co.co_names[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 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, unbound):
self.unbound = unbound
[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.im_self is not None:
input_types = [Const(c.im_self)] + input_types
return infer_return_type_func(c.im_func, input_types, debug, depth)
elif isinstance(c, BoundMethod):
input_types = [c.unbound.im_class] + input_types
return infer_return_type_func(
c.unbound.im_func, input_types, debug, depth)
elif isinstance(c, (type, types.ClassType)):
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:
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
import opcodes
simple_ops = dict((k.upper(), v) for k, v in opcodes.__dict__.items())
co = f.func_code
code = co.co_code
end = len(code)
pc = 0
extended_arg = 0
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)
last_pc = -1
while pc < end:
start = pc
op = ord(code[pc])
if debug:
print '-->' if pc == last_pc else ' ',
print repr(pc).rjust(4),
print dis.opname[op].ljust(20),
pc += 1
if op >= dis.HAVE_ARGUMENT:
arg = ord(code[pc]) + ord(code[pc + 1]) * 256 + extended_arg
extended_arg = 0
pc += 2
if op == dis.EXTENDED_ARG:
extended_arg = arg * 65536L
if debug:
print str(arg).rjust(5),
if op in dis.hasconst:
print '(' + repr(co.co_consts[arg]) + ')',
elif op in dis.hasname:
print '(' + co.co_names[arg] + ')',
elif op in dis.hasjrel:
print '(to ' + repr(pc + arg) + ')',
elif op in dis.haslocal:
print '(' + co.co_varnames[arg] + ')',
elif op in dis.hascompare:
print '(' + dis.cmp_op[arg] + ')',
elif op in dis.hasfree:
if free is None:
free = co.co_cellvars + co.co_freevars
print '(' + free[arg] + ')',
# Acutally 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'):
standard_args = (arg & 0xF) + (arg & 0xF0) / 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 & 0xF0:
# 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]
elif opname in simple_ops:
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 guerenteed 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))
if debug:
print f, id(f), input_types, '->', result
return result