Joel Croteau created THRIFT-4588:
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Summary: local variable referenced before assignment in immutable
python structs
Key: THRIFT-4588
URL: https://issues.apache.org/jira/browse/THRIFT-4588
Project: Thrift
Issue Type: Bug
Components: Python - Compiler
Affects Versions: 0.11.0
Reporter: Joel Croteau
If an immutable struct has unset optional fields, the Python code generated for
it will produce an UnboundLocalError when deserializing it. Consider this
struct:
{code:java}
struct TestStruct {
1: optional i32 value;
} (python.immutable="",)
{code}
Compiling this to Python with Thrift 0.11.0, the ttypes.py has this read method:
{code:java}
@classmethod
def read(cls, iprot):
if iprot._fast_decode is not None and isinstance(iprot.trans,
TTransport.CReadableTransport) and cls.thrift_spec is not None:
return iprot._fast_decode(None, iprot, [cls, cls.thrift_spec])
iprot.readStructBegin()
while True:
(fname, ftype, fid) = iprot.readFieldBegin()
if ftype == TType.STOP:
break
if fid == 1:
if ftype == TType.I32:
value = iprot.readI32()
else:
iprot.skip(ftype)
else:
iprot.skip(ftype)
iprot.readFieldEnd()
iprot.readStructEnd()
return cls(
value=value,
)
{code}
Since no default is ever set for value, if it is never set while reading the
input file, it will attempt to use an unbound variable when creating the class
at the end of this method. For a non-immutable struct, the analogous code is:
{code:java}
def __init__(self, value=None,):
self.value = value
def read(self, iprot):
if iprot._fast_decode is not None and isinstance(iprot.trans,
TTransport.CReadableTransport) and self.thrift_spec is not None:
iprot._fast_decode(self, iprot, [self.__class__, self.thrift_spec])
return
iprot.readStructBegin()
while True:
(fname, ftype, fid) = iprot.readFieldBegin()
if ftype == TType.STOP:
break
if fid == 1:
if ftype == TType.I32:
self.value = iprot.readI32()
else:
iprot.skip(ftype)
else:
iprot.skip(ftype)
iprot.readFieldEnd()
iprot.readStructEnd()
{code}
which works in this case because value is given a default value of None. It
would probably make sense to set value to None at the start of this method.
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