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Remove several deprecated values, especially result-related #968

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Mar 3, 2023
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Remove several deprecated values, especially result-related #968

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12 changes: 12 additions & 0 deletions CHANGES
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,18 @@

* Lwt_result.catch now takes a function (unit -> 'a t) rather than a promise ('a t) (#965)

* Remove the deprecated Lwt.result type (use Stdlib.result instead) (#968)

* Remove the deprecated Lwt.make_value and Lwt.make_result functions (use Ok and Error instead) (#968)

* Remove the deprecated and unsafe waiter_of_wakener (keep the waiter around when you create the wakener instead) (#968)

* Remove the deprecated Lwt_stream.on_termination and Lwt_stream.on_terminate (bind to Lwt_stream.closed instead) (#968)

* Remove the deprecated Lwt_stream.result type (use Stdlib.result instead) (#968)

* Remove the deprecated Lwt_stream.map_exn function (use wrap_exn instead) (#968)

====== Additions ======

* Lwt.reraise an exception raising function which preserves backtraces, recommended for use in Lwt.catch (#963)
Expand Down
70 changes: 19 additions & 51 deletions src/core/lwt.ml
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Expand Up @@ -537,11 +537,6 @@ module Public_types =
struct
type +'a t
type -'a u
(* The contravariance of resolvers is, technically, unsound due to the
existence of [Lwt.waiter_of_wakener]. That is why that function is
deprecated. See

https://github.com/ocsigen/lwt/issues/458 *)

let to_public_promise : ('a, _, _) promise -> 'a t = Obj.magic
let to_public_resolver : ('a, _, _) promise -> 'a u = Obj.magic
Expand Down Expand Up @@ -570,18 +565,10 @@ struct
be optimized away even on older versions of OCaml that don't have Flambda
and don't support [[@@ocaml.unboxed]]. *)



(* Internal name of the public [+'a Lwt.result]. The public name is defined
later in the module. This is to avoid potential confusion with
[Stdlib.result]/[Result.result], as the public name would not be
prefixed with [Lwt.] inside this file. *)
type +'a lwt_result = ('a, exn) Result.t

(* This could probably save an allocation by using [Obj.magic]. *)
let state_of_result = function
| Result.Ok x -> Fulfilled x
| Result.Error exn -> Rejected exn
| Ok x -> Fulfilled x
| Error exn -> Rejected exn
end
include Public_types

Expand Down Expand Up @@ -1341,11 +1328,11 @@ include Resolution_loop

module Resolving :
sig
val wakeup_later_result : 'a u -> 'a lwt_result -> unit
val wakeup_later_result : 'a u -> ('a, exn) result -> unit
val wakeup_later : 'a u -> 'a -> unit
val wakeup_later_exn : _ u -> exn -> unit

val wakeup_result : 'a u -> 'a lwt_result -> unit
val wakeup_result : 'a u -> ('a, exn) result -> unit
val wakeup : 'a u -> 'a -> unit
val wakeup_exn : _ u -> exn -> unit

Expand Down Expand Up @@ -1373,8 +1360,8 @@ struct
ignore p

let wakeup_result r result = wakeup_general "wakeup_result" r result
let wakeup r v = wakeup_general "wakeup" r (Result.Ok v)
let wakeup_exn r exn = wakeup_general "wakeup_exn" r (Result.Error exn)
let wakeup r v = wakeup_general "wakeup" r (Ok v)
let wakeup_exn r exn = wakeup_general "wakeup_exn" r (Error exn)

let wakeup_later_general api_function_name r result =
let Internal p = to_internal_resolver r in
Expand All @@ -1397,9 +1384,9 @@ struct
let wakeup_later_result r result =
wakeup_later_general "wakeup_later_result" r result
let wakeup_later r v =
wakeup_later_general "wakeup_later" r (Result.Ok v)
wakeup_later_general "wakeup_later" r (Ok v)
let wakeup_later_exn r exn =
wakeup_later_general "wakeup_later_exn" r (Result.Error exn)
wakeup_later_general "wakeup_later_exn" r (Error exn)



Expand Down Expand Up @@ -1471,15 +1458,15 @@ module Trivial_promises :
sig
val return : 'a -> 'a t
val fail : exn -> _ t
val of_result : 'a lwt_result -> 'a t
val of_result : ('a, exn) result -> 'a t

val return_unit : unit t
val return_true : bool t
val return_false : bool t
val return_none : _ option t
val return_some : 'a -> 'a option t
val return_ok : 'a -> ('a, _) Result.t t
val return_error : 'e -> (_, 'e) Result.t t
val return_ok : 'a -> ('a, _) result t
val return_error : 'e -> (_, 'e) result t
val return_nil : _ list t

val fail_with : string -> _ t
Expand All @@ -1501,8 +1488,8 @@ struct
let return_nil = return []
let return_true = return true
let return_false = return false
let return_ok x = return (Result.Ok x)
let return_error x = return (Result.Error x)
let return_ok x = return (Ok x)
let return_error x = return (Error x)

let fail_with msg =
to_public_promise {state = Rejected (Failure msg)}
Expand All @@ -1525,8 +1512,6 @@ sig
val wait : unit -> 'a t * 'a u
val task : unit -> 'a t * 'a u

val waiter_of_wakener : 'a u -> 'a t

val add_task_r : 'a u Lwt_sequence.t -> 'a t
val add_task_l : 'a u Lwt_sequence.t -> 'a t

Expand Down Expand Up @@ -1565,12 +1550,6 @@ struct



let waiter_of_wakener r =
let Internal r = to_internal_resolver r in
let p = r in
to_public_promise p



let cast_sequence_node
(node : 'a u Lwt_sequence.node)
Expand Down Expand Up @@ -2637,7 +2616,7 @@ struct
let count_resolved_promises_in (ps : 'a t list) =
let rec count_and_gather_rejected total rejected ps =
match ps with
| [] -> Result.Error (total, rejected)
| [] -> Error (total, rejected)
| p :: ps ->
let Internal q = to_internal_promise p in
match (underlying q).state with
Expand All @@ -2647,7 +2626,7 @@ struct
in
let rec count_fulfilled total ps =
match ps with
| [] -> Result.Ok total
| [] -> Ok total
| p :: ps ->
let Internal q = to_internal_promise p in
match (underlying q).state with
Expand Down Expand Up @@ -2709,7 +2688,7 @@ struct
invalid_arg
"Lwt.choose [] would return a promise that is pending forever";
match count_resolved_promises_in ps with
| Result.Ok 0 ->
| Ok 0 ->
let p = new_pending ~how_to_cancel:(propagate_cancel_to_several ps) in

let callback result =
Expand All @@ -2723,13 +2702,13 @@ struct

to_public_promise p

| Result.Ok 1 ->
| Ok 1 ->
nth_resolved ps 0

| Result.Ok n ->
| Ok n ->
nth_resolved ps (Random.State.int (Lazy.force prng) n)

| Result.Error (n, ps) ->
| Error (n, ps) ->
nth_resolved ps (Random.State.int (Lazy.force prng) n)

let pick ps =
Expand Down Expand Up @@ -3184,14 +3163,3 @@ struct
let (let+) x f = map f x
let (and+) = both
end


module Lwt_result_type =
struct
type +'a result = 'a lwt_result

(* Deprecated. *)
let make_value v = Result.Ok v
let make_error exn = Result.Error exn
end
include Lwt_result_type
60 changes: 5 additions & 55 deletions src/core/lwt.mli
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Expand Up @@ -1600,45 +1600,26 @@ Lwt.fail (Stdlib.Invalid_argument s)

(** {3 Result type} *)

type nonrec +'a result = ('a, exn) result
(** Representation of the content of a resolved promise of type
['a ]{!Lwt.t}.

This type is effectively

{[
type +'a Lwt.result =
| Ok of 'a
| Error of exn
]}

(**
A resolved promise of type ['a ]{!Lwt.t} is either fulfilled with a value of
type ['a], or rejected with an exception.

This corresponds to the cases of a [('a, exn)]{!Stdlib.result}:
fulfilled corresponds to [Ok of 'a], and rejected corresponds to
[Error of exn].

It's important to note that this type constructor, [Lwt.result], is
different from [Stdlib.result]. It is a specialization of [Stdlib.result] so
that the [Error] constructor always carries [exn].

For Lwt programming with [result] where the [Error] constructor can carry
arbitrary error types, see module {!Lwt_result}.

The naming conflict between [Lwt.result] and [Stdlib.result] is an
unfortunate historical accident. [Stdlib.result] did not exist when
[Lwt.result] was created. *)
arbitrary error types, see module {!Lwt_result}. *)

val of_result : 'a result -> 'a t
val of_result : ('a, exn) result -> 'a t
(** [Lwt.of_result r] converts an r to a resolved promise.

- If [r] is [Ok v], [Lwt.of_result r] is [Lwt.return v], i.e. a promise
fulfilled with [v].
- If [r] is [Error exn], [Lwt.of_result r] is [Lwt.fail exn], i.e. a promise
rejected with [exn]. *)

val wakeup_later_result : 'a u -> 'a result -> unit
val wakeup_later_result : 'a u -> ('a, exn) result -> unit
(** [Lwt.wakeup_later_result r result] resolves the pending promise [p]
associated to resolver [r], according to [result]:

Expand Down Expand Up @@ -1802,43 +1783,12 @@ val wakeup_exn : _ u -> exn -> unit
(** [Lwt.wakeup_exn r exn] is like {!Lwt.wakeup_later_exn}[ r exn], but has
the same problems as {!Lwt.wakeup}. *)

val wakeup_result : 'a u -> 'a result -> unit
val wakeup_result : 'a u -> ('a, exn) result -> unit
(** [Lwt.wakeup_result r result] is like {!Lwt.wakeup_later_result}[ r result],
but has the same problems as {!Lwt.wakeup}. *)



(** {3 Helpers for resolving} *)

val make_value : 'a -> 'a result
[@@ocaml.deprecated
" Use Ok (from Stdlib) instead."]
(** [Lwt.make_value v] is equivalent to
{{: https://ocaml.org/api/Stdlib.html#TYPEresult}
[Ok v]}.

@deprecated Use [Ok] instead *)

val make_error : exn -> _ result
[@@ocaml.deprecated
" Use Error (from Stdlib) instead."]
(** [Lwt.make_error exn] is equivalent to
{{: https://ocaml.org/api/Stdlib.html#TYPEresult}
[Error exn]}.

@deprecated Use [Error] (from Stdlib) instead. *)

val waiter_of_wakener : 'a u -> 'a t
[@@ocaml.deprecated
" This function should be avoided, because it makes subtyping of resolvers
unsound. See
https://github.com/ocsigen/lwt/issues/458"]
(** [Lwt.waiter_of_wakener r] evaluates to the promise associated with resolver
[r].

@deprecated Keep the reference to the promise instead. *)



(** {3 Linked lists of promises} *)

Expand Down
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