_callers.py

"""
Call loop machinery
"""
import sys

from ._result import HookCallError, _Result, _raise_wrapfail


def _multicall(hook_name, hook_impls, caller_kwargs, firstresult):
    """Execute a call into multiple python functions/methods and return the
    result(s).

    ``caller_kwargs`` comes from _HookCaller.__call__().
    """
    __tracebackhide__ = True
    results = []
    excinfo = None

    # run impl and wrapper setup functions in a loop
    teardowns = []
    try:
        for hook_impl in reversed(hook_impls):
            try:
                args = [caller_kwargs[argname] for argname in hook_impl.argnames]
            except KeyError:
                for argname in hook_impl.argnames:
                    if argname not in caller_kwargs:
                        raise HookCallError(
                            "hook call must provide argument %r" % (argname,)
                        )

            if hook_impl.hookwrapper:
                try:
                    gen = hook_impl.function(*args)
                    next(gen)  # first yield
                    teardowns.append(gen)
                except StopIteration:
                    _raise_wrapfail(gen, "did not yield")
            else:
                res = hook_impl.function(*args)
                if res is not None:
                    results.append(res)
                    if firstresult:  # halt further impl calls
                        break
    except BaseException:
        excinfo = sys.exc_info()

    if firstresult:  # first result hooks return a single value
        outcome = _Result(results[0] if results else None, excinfo)
    else:
        outcome = _Result(results, excinfo)

    # run all wrapper post-yield blocks
    for gen in reversed(teardowns):
        try:
            gen.send(outcome)
            _raise_wrapfail(gen, "has second yield")
        except StopIteration:
            pass

    return outcome.get_result()