Function _expand_output_spec

dash/mcp/primitives/tools/callback_adapter.py:385–430

Build the outputs spec, expanding wildcards to concrete IDs. For wildcard outputs, derives concrete IDs from the resolved inputs. The browser does the same: input and output wildcards resolve against the same set of matching components.

(
    output_id: str,
    cb_info: dict,
    resolved_inputs: list[CallbackInputs],
)

def _expand_output_spec(
    output_id: str,
    cb_info: dict,
    resolved_inputs: list[CallbackInputs],
) -> CallbackOutputTarget | list[CallbackOutputTarget]:
    """Build the outputs spec, expanding wildcards to concrete IDs.

    For wildcard outputs, derives concrete IDs from the resolved inputs.
    The browser does the same: input and output wildcards resolve against
    the same set of matching components.
    """
    if cb_info.get("no_output"):
        return []

    parsed = split_callback_id(output_id)
    if isinstance(parsed, dict):
        parsed = [parsed]

    results: list[CallbackOutputTarget] = []
    for p in parsed:
        pid = p["id"]
        prop = clean_property_name(p["property"])
        pattern = parse_wildcard_id(pid)
        if pattern is not None:
            concrete_ids = _derive_output_ids(pattern, resolved_inputs)
            if not concrete_ids:
                concrete_ids = [
                    getattr(comp, "id") for comp in find_matching_components(pattern)
                ]
            expanded: list[CallbackDependency] = [
                CallbackDependency(id=cid, property=prop) for cid in concrete_ids
            ]
            # ALL/ALLSMALLER → nested list; MATCH → single dict
            if len(expanded) == 1:
                results.append(expanded[0])
            else:
                results.append(expanded)
        else:
            results.append(CallbackDependency(id=pid, property=prop))

    # Mirror the Dash renderer: single-output callbacks send a bare dict,
    # multi-output callbacks send a list. The framework's output value
    # matching depends on this shape.
    if len(results) == 1:
        return results[0]
    return results


def _derive_output_ids(