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Merged
merged 5 commits into from
Sep 9, 2019
Merged

Improve __bool__ #1354

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747f777
Add test code from the CPython repository(Lib/test/test_bool.py).
ChJR Aug 16, 2019
adc919f
Merge branch 'master' into feature/__bool__
ChJR Sep 8, 2019
7b98092
Check __bool__() returns only bool value
ChJR Sep 8, 2019
21821b7
Throw ValueError when __len__() is a negative value
ChJR Sep 8, 2019
da02029
Refactor boolval()
ChJR Sep 8, 2019
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37 changes: 36 additions & 1 deletion tests/snippets/bools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -142,4 +142,39 @@ def __len__(self):


with assertRaises(TypeError):
bool(TestLenThrowError())
bool(TestLenThrowError())

# Verify that TypeError occurs when bad things are returned
# from __bool__(). This isn't really a bool test, but
# it's related.
def check(o):
with assertRaises(TypeError):
bool(o)

class Foo(object):
def __bool__(self):
return self
check(Foo())

class Bar(object):
def __bool__(self):
return "Yes"
check(Bar())

class Baz(int):
def __bool__(self):
return self
check(Baz())

# __bool__() must return a bool not an int
class Spam(int):
def __bool__(self):
return 1
check(Spam())

class Eggs:
def __len__(self):
return -1

with assertRaises(ValueError):
bool(Eggs())
27 changes: 18 additions & 9 deletions vm/src/obj/objbool.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
use num_bigint::Sign;
use num_traits::Zero;

use crate::function::PyFuncArgs;
Expand Down Expand Up @@ -29,22 +30,30 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
// If descriptor returns Error, propagate it further
let method = method_or_err?;
let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
match bool_obj.payload::<PyInt>() {
Some(int_obj) => !int_obj.as_bigint().is_zero(),
None => {
return Err(vm.new_type_error(format!(
"__bool__ should return bool, returned type {}",
bool_obj.class().name
)))
}
if !objtype::isinstance(&bool_obj, &vm.ctx.bool_type()) {
return Err(vm.new_type_error(format!(
"__bool__ should return bool, returned type {}",
bool_obj.class().name
)));
}

get_value(&bool_obj)
}
None => match vm.get_method(obj.clone(), "__len__") {
Some(method_or_err) => {
let method = method_or_err?;
let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
match bool_obj.payload::<PyInt>() {
Some(int_obj) => !int_obj.as_bigint().is_zero(),
Some(int_obj) => {
let len_val = int_obj.as_bigint();
if len_val.sign() == Sign::Minus {
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Do we prefer to have if-else block than this pattern?

if len_val.sign() == Sign::Minus {
   Err(
      vm.new_value_error("__len__() should return >= 0".to_string())
    )
} else {
    !len_val.is_zero()
}

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It would still have to return the error, as the result of that expression is a bool and not a Result.

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Oh, it must escape from the function, i got it.

return Err(
vm.new_value_error("__len__() should return >= 0".to_string())
);
}

!len_val.is_zero()
}
None => {
return Err(vm.new_type_error(format!(
"{} object cannot be interpreted as integer",
Expand Down