I just wanted to follow up and summarize here. I submitted a PR https://github.com/elixir-lang/elixir/pull/9773 with some more discussion, but the core point there was that we needed more discussion on the core list before a PR and it was closed. Nil-safety by default is undesirable in more Access functions than Access.get.
I'm exploring this on my own in my own codebase as I rework all the get_in calls I assumed were nil safe despite using Access.at. I am quite against a solution that is more verbose to gain mil safety as I use this at the edges of my system in an anti-corruption-layer. I'd rather see this implemented once, well, in the standard library than expect thousands of projects to do it themselves or bring in a 3rd party solutions to achieve it. Feel free to discuss some more. -Greg > On Jan 30, 2020, at 12:02 PM, Allen Madsen <allen.c.mad...@gmail.com> wrote: > > I'm in favor of them being nilsafe by default. > > Allen Madsen > http://www.allenmadsen.com > > > On Wed, Jan 29, 2020 at 11:24 AM Tor Bjornrud <bjorn...@gmail.com> wrote: > I wouldn't mind having opts for something like this. Avoids creating a slew > of Access functions that then become difficult to sift through. > > %{"items" => nil} |> get_in(["items", Access.at(0, nilsafe: true) > > On Tuesday, January 28, 2020 at 8:10:04 PM UTC-6, Greg Vaughn wrote: > Thanks, José. I agree with the need to be consistent. I will look at the > bigger picture, though, like Manfred I find the addition of "maybe" to be > awkward, so my preference is to have the existing recommended functions in > the Access module intended for use with get_in to be consistently nil safe. > I'm open to more ideas, too. > > -Greg Vaughn > > > On Jan 28, 2020, at 12:45 PM, José Valim <jose...@dashbit.co> wrote: > > > > The proposal is reasonable however it would introduce an inconsistency > > since the other selectors in Access, such as Access.key, are also not nil > > safe. So whatever solution we choose needs to be consistent. > > > > One possible suggestion is to introduce a "Access.maybe" that composes but > > composition would have to be back to front: > > > > %{"items" => nil} |> get_in(["items", Access.at(0) |> Access.maybe]) > > > > Another idea is to introduce maybe_at, maybe_key, maybe_key! and so on. But > > I am not sure if this is desirable. Thoughts? > > > > On Tue, Jan 28, 2020 at 7:33 PM Greg Vaughn <gva...@gmail.com> wrote: > > I propose that the function returned from Access.at/1 special case nil such > > that the overall Kernel.get_in/2 call returns nil instead of raising an > > error. > > > > Rationale: > > I originally blamed this on Kernel.get_in/2 and I'd like to thank Eric > > Meadows-Jönsson for explaining the underlying reason to me on Slack. > > > > I like to think of Kernel.get_in/2 as a nil-safe way of plucking values out > > of nested data structures, but I learned today that is only partially > > correct. The nil-safety comes from the underlying Access.get/2 calls. The > > docs for get_in includes: > > > > In case any of the entries in the middle returns nil, nil will be returned > > as per the Access module: > > iex> users = %{"john" => %{age: 27}, "meg" => %{age: 23}} > > iex> get_in(users, ["unknown", :age]) > > nil > > > > and I expected use of Access.at/1 in my keys to act similarly, but it > > doesn't. For example: > > > > iex(185)> %{"items" => ["desired_value"]} |> get_in(["items", > > Access.at(0)]) > > "desired_value" > > iex(186)> %{"items" => nil} |> get_in(["items", Access.at(0)]) > > ** (RuntimeError) Access.at/1 expected a list, got: nil > > (elixir) lib/access.ex:663: Access.at/4 > > > > I propose that the function returned from Access.at/1 special case nil such > > that the overall get_in/2 call returns nil instead of raising an error. I > > have not dug into the source yet but I'm happy to work up a PR if there is > > interest in this change. > > > > -Greg Vaughn > > > > -- > > 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-l...@googlegroups.com. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/elixir-lang-core/6B6AB775-F3D5-40E5-BFBD-9852FBCBD1D0%40gmail.com. > > > > > > -- > > 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-l...@googlegroups.com. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4KZPZ5mpP6SSzhmq3jpuZBYA1irpmOa19UNH2fS_3QKQA%40mail.gmail.com. > > > > > -- > 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/1ae0b9d3-9471-4750-8734-281033e9a1dc%40googlegroups.com. > > -- > 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/CAK-y3Cu%2BGBO1RWsdAjAHoaukV3w4QJPPdqqNU_miQ_%3Dv5%3DdDeQ%40mail.gmail.com. -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. 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