python-botocore-validator-fuzzy-op-matching

Answer

Root cause. aws-shape-validator.py matched handler ops to AWS ops with a substring test on normalized names:

def _match(handler: str, aws_op: str) -> bool:
    return _normalize(handler) in _normalize(aws_op)   # BUG: substring

DeleteExperimentTemplate contains DeleteExperiment as a substring, so the fis handler delete-experiment fuzzy-matched the wrong op. The shape validator then looked for the Experiment shape on DeleteExperimentTemplate (whose request shape has only Id) and crashed with Experiment not found.

Fix. A handler name must be a suffix of the AWS op name (endswith), not merely a substring. Normalize both sides (lowercase, strip -/_/spaces) so kebab/snake/camel agree, then require endswith:

def _normalize(name: str) -> str:
    return re.sub(r"[\s_-]+", "", name).lower()

def _match(handler: str, aws_op: str) -> bool:
    h, op = _normalize(handler), _normalize(aws_op)
    return bool(h) and op.endswith(h)   # FIX: suffix, not substring

With this, deleteexperimenttemplate no longer ends with deleteexperiment (it ends with experimenttemplate), so delete-experiment resolves only to DeleteExperiment.

One hardening step that falls out of the sweep. Plain endswith still lets tag-resource match UntagResource (untagresource ends with tagresource). The strict-suffix resolver keeps endswith as the acceptance test but, when several true suffixes qualify, picks the longest match, so UntagResource binds to untag-resource, TagResource to tag-resource, DeleteExperimentTemplate to delete-experiment-template, and DeleteExperiment to delete-experiment. Any op with no suffix-matching handler, a tie, a handler claimed twice, or an unused handler fails loudly:

def resolve(handlers, ops):
    mapping, used = {}, set()
    for op in sorted(ops):
        n_op = _normalize(op)
        candidates = [h for h in handlers if n_op.endswith(_normalize(h))]
        if not candidates:
            raise ValueError(f"op {op} has no suffix-matching handler")
        best = max(candidates, key=lambda h: len(_normalize(h)))
        ties = [h for h in candidates if len(_normalize(h)) == len(_normalize(best))]
        if len(ties) > 1:
            raise ValueError(f"op {op} suffix tie: {ties}")
        if best in used:
            raise ValueError(f"handler {best} claimed by multiple ops")
        mapping[best], used.add(best) = op, None
    if unused := set(handlers) - set(mapping):
        raise ValueError(f"handlers with no op: {sorted(unused)}")
    return mapping