Instead of creating a new struct, which would require changing many modules, I would build a regular Task and then send a message to myself in the form {ref, result}. :)
On Thu, Jul 1, 2021 at 7:50 PM Aaron Ross <superhawk...@gmail.com> wrote: > I put together a PR here: https://github.com/superhawk610/elixir/pull/1 > > I'd love to hear any feedback on the approach and implementation before > submitting to the official repo. > > Thanks in advance! > > On Thursday, July 1, 2021 at 12:33:57 AM UTC-7 José Valim wrote: > >> It sounds good to me. A small but likely welcome change. A PR to further >> explore this is welcome! >> >> On Thu, Jul 1, 2021 at 12:26 AM Aaron Ross <superh...@gmail.com> wrote: >> >>> +1 >>> >>> I've encountered this in a similar context - I have one overall task >>> that will spawn some number of data fetching tasks, but in some cases I >>> know that the data fetch call will return no results so I stub the task >>> with `Task.async(fn -> {:ok, []} end)`. The proposed `Task.completed/1` >>> would be a great, more semantic replacement and has the benefit of not >>> spawning an unneeded process. >>> >>> On Wednesday, June 30, 2021 at 3:22:07 PM UTC-7 Luke Bakken wrote: >>> >>>> ## Background >>>> >>>> I have an enumerable over which I fold and call Task.async based on the >>>> data in the enumerable. I then Task.yield_many over the list of tasks, and >>>> use Enum.zip to correlate the original enumerable with the results. >>>> >>>> I have a case where, during the fold I find that an entry is invalid >>>> for running Task.async. It would be convenient to create an "already >>>> completed" Task that contains an error result. For now, I'm still using >>>> Task.async to basically return an :error tuple, which of course starts and >>>> links a process. >>>> >>>> Of course, I could work around this by using maps, etc. >>>> >>>> I tried using %Task{} to create a "dummy" but calling Task.yield_many >>>> with such an entry always blocks until the timeout. >>>> >>>> ## Proposal >>>> >>>> Add Task.completed/1 that creates an "already completed" Task that can >>>> then be awaited / yielded to return the result used when completed/1 was >>>> called: >>>> >>>> ```elixir >>>> task = Task.completed({:error, :boom}) >>>> ``` >>>> >>>> Awaiting or yielding on such a task returns the result immediately >>>> without invoking a process. >>>> >>>> ## Other >>>> >>>> .NET has the following to achieve this behavior, for instance: >>>> >>>> >>>> https://docs.microsoft.com/en-us/dotnet/api/system.threading.tasks.task.completedtask?view=net-5.0 >>>> >>>> >>>> https://docs.microsoft.com/en-us/dotnet/api/system.threading.tasks.task.fromresult?view=net-5.0 >>>> >>>> Thanks for your consideration! If approved I would gladly implement >>>> this. >>>> Luke >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "elixir-lang-core" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to elixir-lang-co...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/d12a9c8c-6441-48d7-9ebe-1194abb86f30n%40googlegroups.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/d12a9c8c-6441-48d7-9ebe-1194abb86f30n%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/757ee481-333d-4f11-b668-e89b62eb598en%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/757ee481-333d-4f11-b668-e89b62eb598en%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4K4v3uQ4AzyCqdWbZ3aBm4ipm2BTxvjwV%3DoDnmYYthLCw%40mail.gmail.com.