ARCHIVED TRAINING / enthought/traits

enthought__traits-1534

This is a preserved training example. Membership in the current training wave has not been verified.

Problem statement

Bad default value handling for Union
In #1522, I introduced the following bug, which broke the Pyface test suite:

```python
Python 3.9.7 (default, Sep  1 2021, 04:00:27) 
[Clang 11.0.3 (clang-1103.0.32.62)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from traits.api import *
>>> class A(HasTraits):
...     foo = Union(None, Int)
... 
>>> class B(A):
...     foo = 5
... 
>>> b = B()
>>> b.foo -= 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -=: '_Undefined' and 'int'
```

Training membership

opd_e4b_pure_v6b

Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.

Task and snapshot provenance

Snapshot captured 2026-11-12T17:06:59.476467+00:00 · Autoresearch-Arena/gemma-4-developer-agent

{
  "datasets": [
    "opd_e4b_pure_v6b"
  ],
  "examples": 3,
  "instance_id": "enthought__traits-1534",
  "problem_statement": "Bad default value handling for Union\nIn #1522, I introduced the following bug, which broke the Pyface test suite:\r\n\r\n```python\r\nPython 3.9.7 (default, Sep  1 2021, 04:00:27) \r\n[Clang 11.0.3 (clang-1103.0.32.62)] on darwin\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n>>> from traits.api import *\r\n>>> class A(HasTraits):\r\n...     foo = Union(None, Int)\r\n... \r\n>>> class B(A):\r\n...     foo = 5\r\n... \r\n>>> b = B()\r\n>>> b.foo -= 1\r\nTraceback (most recent call last):\r\n  File \"<stdin>\", line 1, in <module>\r\nTypeError: unsupported operand type(s) for -=: '_Undefined' and 'int'\r\n```",
  "repo": "enthought/traits",
  "source": "v2/experiments/train_data/opd_e4b_pure_v6b/verified_rft_messages.jsonl",
  "source_sha256": "0f62460a9706eea5e1605255896f191ab00cb5706c5f1f2e1c293e9a718218dc"
}

{
  "captured_at": "2026-11-12T17:06:59.476467+00:00",
  "membership": "archived training",
  "membership_evidence": "Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.",
  "name": "Preserved post-training task archive",
  "source": "Autoresearch-Arena/gemma-4-developer-agent",
  "source_revision": "016496de222aaafca0d4ee4c18efc63ba616f76e",
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      "sha256": "a42453ccd7ac7680b0a03865e8e7080bc8bf74c8d9d193b440c441ed46f8512b"
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}