NAME

       "Future::AsyncAwait::Awaitable" - the interface required by "Future::AsyncAwait"

DESCRIPTION

       This module documents the method interface required by "Future::AsyncAwait" to operate on
       future instances returned by expressions invoked by the "await" keyword, and returned by
       functions declared by "async sub". This information is largely of relevance to
       implementors of other module integrations, event systems, or similar. It is not necessary
       to make regular use of the syntax provided by the module when working with existing event
       systems.

       The methods required by this interface are all capitalised and prefixed with "AWAIT_...",
       ensuring they are unlikely to clash with existing methods on a class which may have
       differing semantics.

   Role::Tiny
       If Role::Tiny is available, this module declares itself to be a role that requires the
       following named methods. The role supplies no code to the applied class, but can be useful
       for checking that you have in fact implemented all of the required methods.

   Conformance Test
       To assist implementors of alternative future-like classes, an API conformance test suite
       is provided by Test::Future::AsyncAwait::Awaitable. You may find this useful to check that
       your implementation is suitable.

CONSTRUCTORS

       The following methods are expected to create new future instances. They make use of the
       class set by the prevailing "future_class" import argument, if set, or default to "Future"
       if not.

   AWAIT_NEW_DONE
       Generate a new immediate future that is successful. The future will already be ready and
       have the list of values set as its result.

          $f = $CLASS->AWAIT_NEW_DONE( @results )

          # $f->AWAIT_IS_READY will be true
          # $f->AWAIT_GET will return @results

   AWAIT_NEW_FAIL
       Generate a new immediate future that is failed. The future will already be ready and
       invoking the "AWAIT_GET" method will throw the given exception.

          $f = $CLASS->AWAIT_NEW_FAIL( $message )

          # $f->AWAIT_IS_READY will be true
          # $f->AWAIT_GET will throw $message

INSTANCE METHODS

   AWAIT_CLONE
       Generate a new pending future of the same type as an existing one, which is not modified
       by doing so. It will only be invoked on instances that are currently pending.

          $new_f = $f->AWAIT_CLONE

       If the instance has any fields that are required for successful operation (such as
       application-wide context or event system components) these ought to be copied. The method
       should not otherwise copy any per-instance state such as pending callbacks or partial
       results.

   AWAIT_DONE
       Sets the success result of an existing still-pending future. It will only be invoked on
       future instances that are currently pending.

          $f->AWAIT_DONE( @results )

          # $f->AWAIT_IS_READY will now be true
          # $f->AWAIT_GET will now return @results

   AWAIT_FAIL
       Sets the failure result of an existing still-pending future. It will only be invoked on
       future instances that are currently pending.

          $f->AWAIT_FAIL( $message )

          # $f->AWAIT_IS_READY will now be true
          # $f->AWAIT_GET will now throw $message

   AWAIT_IS_READY
       Returns true if a future is ready (successful, failed or cancelled); false if still
       pending.

          $bool = $f->AWAIT_IS_READY

   AWAIT_IS_CANCELLED
       Returns true is a future has already been cancelled; false if still pending, successful or
       failed.

          $bool = $f->AWAIT_IS_CANCELLED

       An implementation that does not support cancellation can simply return a constant false
       here:

          sub AWAIT_IS_CANCELLED { 0 }

   AWAIT_GET
       Yields the result of a successful future (or just the first value if called in scalar
       context). Throws the failure message as an exception if called on a a failed one. Will not
       be invoked on a pending or cancelled future.

          @result = $f->AWAIT_GET
          $result = $f->AWAIT_GET
          $f->AWAIT_GET

   AWAIT_ON_READY
       Attach a new CODE reference to be invoked when the future becomes ready (by success or
       failure). The arguments and context that $code is invoked with are unspecified.

          $f->AWAIT_ON_READY( $code )

   AWAIT_CHAIN_CANCEL
       Attach a future instance to be cancelled when another one is cancelled.

          $f1->AWAIT_CHAIN_CANCEL( $f2 )

       When $f1 is cancelled, then $f2 is cancelled. There is no link from $f2 back to $f1 -
       whenever $f2 changes state here, nothing special happens to $f1.

       An implementation that does not support cancellation can simply ignore this method.

          sub AWAIT_CHAIN_CANCEL { }

       An older version of this API specification named this "AWAIT_ON_CANCEL", but that name
       will be repurposed for attaching code blocks in a later version.

   AWAIT_ON_CANCEL
       Attach a new CODE reference to be invoked when the future is cancelled.

          $f->AWAIT_ON_CANCEL( $code )

       An implementation that does not support cancellation can simply ignore this method.

          sub AWAIT_ON_CANCEL { }

   AWAIT_WAIT
       Called by the toplevel "await" expression in order to run the event system and wait for
       the instance to be ready. It should return results or throw an exception in the same
       manner as "AWAIT_GET".

          @result = $f->AWAIT_WAIT
          $result = $f->AWAIT_WAIT
          $f->AWAIT_WAIT

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>