[Bug]: ascii() does not preserve str subclass type for all-ASCII repr #686
Description
Describe the bug
ascii() returns a plain str instead of preserving the str subclass type when __repr__ returns an all-ASCII str subclass instance. This is a CPython compatibility issue.
Operating system
Linux
CPU architecture
ARM64
GraalPy version
25.0.2
JDK version
No response
Context configuration
No response
Steps to reproduce
class MyStr(str):
pass
class Foo:
def __repr__(self):
return MyStr('hello')
result = ascii(Foo())
print(result)
print(type(result))GraalPy (Actual):
hello
<class 'str'>
CPython (Expected):
hello
<class '__main__.MyStr'>
Additional context
Root Cause
PyObjectAsciiNode.java#L77-L87 uses PyObjectReprAsTruffleStringNode, which converts the repr result to a raw TruffleString via CastToTruffleStringNode, discarding the PString subclass wrapper. When the repr is all-ASCII, the node returns that bare TruffleString — a plain str — instead of the original object.
CPython reference:
Objects/object.c#L514-L523—PyObject_ASCIIdoesif (PyUnicode_IS_ASCII(repr)) return repr, preserving the str subclass type.
Fix Suggestion
Use PyObjectReprAsObjectNode instead of PyObjectReprAsTruffleStringNode and return the original repr object on the all-ASCII fast path to preserve the str subclass type.