Module Tezos_error_monad.Error_monad

type error_category = [
| `Branch

Errors that may not happen in another context

| `Temporary

Errors that may not happen in a later context

| `Permanent

Errors that will happen no matter the context


Categories of error

type error = TzCore.error = ..
include Sig.CORE with type error := error
type error
val error_encoding : error Data_encoding.t
val pp : Stdlib.Format.formatter -> error -> unit
include Sig.EXT with type error := error
type error = ..
val register_error_kind : Sig.error_category -> id:string -> title:string -> description:string -> ?⁠pp:(Stdlib.Format.formatter -> 'err -> unit) -> 'err Data_encoding.t -> (error -> 'err option) -> ('err -> error) -> unit

The error data type is extensible. Each module can register specialized error serializers id unique name of this error. Ex.: overflow_time_counter title more readable name. Ex.: Overflow of time counter description human readable description. Ex.: The time counter overflowed while computing delta increase pp formatter used to pretty print additional arguments. Ex.: The time counter overflowed while computing delta increase. Previous value %d. Delta: %d encoder decoder data encoding for this error. If the error has no value, specify Data_encoding.empty

val register_recursive_error_kind : Sig.error_category -> id:string -> title:string -> description:string -> pp:(Stdlib.Format.formatter -> 'err -> unit) -> (error Data_encoding.t -> 'err Data_encoding.t) -> (error -> 'err option) -> ('err -> error) -> unit

Same as register_error_kind but allow errors to wrap other errors.

The encoding argument is a function which will be given the encoding of errors as argument so that you can encode errors in errors using a fixpoint.

Another difference with register_error_kind is that pp is mandatory.

val classify_error : error -> Sig.error_category

Classify an error using the registered kinds

type error += Unclassified of string

Catch all error when 'serializing' an error.

type error += Unregistered_error of Data_encoding.json
val json_of_error : error -> Data_encoding.json

An error serializer

val error_of_json : Data_encoding.json -> error

Error documentation

type error_info = {
category : Sig.error_category;
id : string;
title : string;
description : string;
schema : Data_encoding.json_schema;

Error information

val pp_info : Stdlib.Format.formatter -> error_info -> unit
val find_info_of_error : error -> error_info

find_info_of_error e retrieves the `error_info` associated with the given error `e`.

raises [Invalid_argument]

if the error is a wrapped error from another monad

raises [Not_found]

if the error's constructor has not been registered

val get_registered_errors : unit -> error_info list

Retrieves information of registered errors

include Sig.WITH_WRAPPED with type error := error
type error
module type Wrapped_error_monad = sig ... end
val register_wrapped_error_kind : (module Wrapped_error_monad) -> id:string -> title:string -> description:string -> unit

Same as register_error_kind but for a wrapped error monad. The codec is defined in the module parameter. It makes the category of the error Wrapped instead of Main.

module TzTrace : Sig.TRACE with type 'error trace = 'error list
type 'error trace = 'error TzTrace.trace
include Sig.MONAD with type 'error trace := 'error TzTrace.trace
type 'err trace

To be subsituted/constrained

val ok : 'a -> ('a'trace) Stdlib.result

Successful result

val ok_unit : (unit, 'trace) Stdlib.result
val ok_none : ('a option'trace) Stdlib.result
val ok_some : 'a -> ('a option'trace) Stdlib.result
val ok_nil : ('a list'trace) Stdlib.result
val ok_true : (bool, 'trace) Stdlib.result
val ok_false : (bool, 'trace) Stdlib.result
val return : 'a -> ('a'trace) Stdlib.result Lwt.t

Successful return

val return_unit : (unit, 'trace) Stdlib.result Lwt.t

Successful return of ()

val return_none : ('a option'trace) Stdlib.result Lwt.t

Successful return of None

val return_some : 'a -> ('a option'trace) Stdlib.result Lwt.t

return_some x is a successful return of Some x

val return_nil : ('a list'trace) Stdlib.result Lwt.t

Successful return of []

val return_true : (bool, 'trace) Stdlib.result Lwt.t

Successful return of true

val return_false : (bool, 'trace) Stdlib.result Lwt.t

Successful return of false

val error : 'err -> ('a'err trace) Stdlib.result

Erroneous result

val fail : 'err -> ('a'err trace) Stdlib.result Lwt.t

Erroneous return

val (>>=) : 'a Lwt.t -> ('a -> 'b Lwt.t) -> 'b Lwt.t

Lwt's bind reexported. Following Lwt's convention, in this operator and the ones below, = indicate we operate within Lwt.

val (>|=) : 'a Lwt.t -> ('a -> 'b) -> 'b Lwt.t

Lwt's map reexported. The | indicates a map rather than a bind.

val (>>?) : ('a'trace) Stdlib.result -> ('a -> ('b'trace) Stdlib.result) -> ('b'trace) Stdlib.result

Non-Lwt bind operator. In this operator and the ones below, ? indicates that we operate within the error monad.

val (>|?) : ('a'trace) Stdlib.result -> ('a -> 'b) -> ('b'trace) Stdlib.result

Non-Lwt map operator.

val (>>=?) : ('a'trace) Stdlib.result Lwt.t -> ('a -> ('b'trace) Stdlib.result Lwt.t) -> ('b'trace) Stdlib.result Lwt.t

Combined bind operator. The =? indicates that the operator acts within the combined error-lwt monad.

val (>|=?) : ('a'trace) Stdlib.result Lwt.t -> ('a -> 'b) -> ('b'trace) Stdlib.result Lwt.t

Combined map operator.

val (>>?=) : ('a'trace) Stdlib.result -> ('a -> ('b'trace) Stdlib.result Lwt.t) -> ('b'trace) Stdlib.result Lwt.t

Injecting bind operator. This is for transitioning from the simple Error monad to the combined Error-Lwt monad.

Note the order of the character: it starts with the error monad marker ? and has the Lwt monad marker later. This hints at the role of the operator to transition into Lwt.

val (>|?=) : ('a'trace) Stdlib.result -> ('a -> 'b Lwt.t) -> ('b'trace) Stdlib.result Lwt.t

Injecting map operator.

val record_trace : 'err -> ('a'err trace) Stdlib.result -> ('a'err trace) Stdlib.result

Enrich an error report (or do nothing on a successful result) manually

val trace : 'err -> ('b'err trace) Stdlib.result Lwt.t -> ('b'err trace) Stdlib.result Lwt.t

Automatically enrich error reporting on stack rewind

val record_trace_eval : (unit -> ('err'err trace) Stdlib.result) -> ('a'err trace) Stdlib.result -> ('a'err trace) Stdlib.result

Same as record_trace, for unevaluated error

val trace_eval : (unit -> ('err'err trace) Stdlib.result Lwt.t) -> ('b'err trace) Stdlib.result Lwt.t -> ('b'err trace) Stdlib.result Lwt.t

Same as trace, for unevaluated Lwt error

val error_unless : bool -> 'err -> (unit, 'err trace) Stdlib.result

Error on failed assertion

val error_when : bool -> 'err -> (unit, 'err trace) Stdlib.result
val fail_unless : bool -> 'err -> (unit, 'err trace) Stdlib.result Lwt.t

Erroneous return on failed assertion

val fail_when : bool -> 'err -> (unit, 'err trace) Stdlib.result Lwt.t
val unless : bool -> (unit -> (unit, 'trace) Stdlib.result Lwt.t) -> (unit, 'trace) Stdlib.result Lwt.t
val when_ : bool -> (unit -> (unit, 'trace) Stdlib.result Lwt.t) -> (unit, 'trace) Stdlib.result Lwt.t
val dont_wait : (exn -> unit) -> ('trace -> unit) -> (unit -> (unit, 'trace) Stdlib.result Lwt.t) -> unit

Wrapper around Lwt_utils.dont_wait

val join_p : unit Lwt.t list -> unit Lwt.t

A few aliases for Lwt functions

val all_p : 'a Lwt.t list -> 'a list Lwt.t
val both_p : 'a Lwt.t -> 'b Lwt.t -> ('a * 'b) Lwt.t
val join_e : (unit, 'err trace) Stdlib.result list -> (unit, 'err trace) Stdlib.result

Similar functions in the error monad

val all_e : ('a'err trace) Stdlib.result list -> ('a list'err trace) Stdlib.result
val both_e : ('a'err trace) Stdlib.result -> ('b'err trace) Stdlib.result -> ('a * 'b'err trace) Stdlib.result
val join_ep : (unit, 'err trace) Stdlib.result Lwt.t list -> (unit, 'err trace) Stdlib.result Lwt.t

Similar functions in the combined monad

val all_ep : ('a'err trace) Stdlib.result Lwt.t list -> ('a list'err trace) Stdlib.result Lwt.t
val both_ep : ('a'err trace) Stdlib.result Lwt.t -> ('b'err trace) Stdlib.result Lwt.t -> ('a * 'b'err trace) Stdlib.result Lwt.t
include Sig.MONAD_EXT with type error := error and type 'error trace := 'error TzTrace.trace
type error

for substitution

type 'error trace
type tztrace = error trace
type 'a tzresult = ('atztrace) Stdlib.result
val classify_errors : tztrace -> Sig.error_category
val pp_print_error : Stdlib.Format.formatter -> error trace -> unit
val pp_print_error_first : Stdlib.Format.formatter -> error trace -> unit

Pretty prints a trace as the message of its first error

val trace_encoding : error trace Data_encoding.t
val result_encoding : 'a Data_encoding.t -> 'a tzresult Data_encoding.t

A serializer for result of a given type

val generic_error : ('a, Stdlib.Format.formatter, unit, 'b tzresult) Stdlib.format4 -> 'a

Erroneous result (shortcut for generic errors)

val failwith : ('a, Stdlib.Format.formatter, unit, 'b tzresult Lwt.t) Stdlib.format4 -> 'a

Erroneous return (shortcut for generic errors)

val error_exn : exn -> 'a tzresult
val error_of_exn : exn -> error trace

error_of_exn e is a trace that carries the exception e. This function is intended to be used when interacting with a part of the code (most likely an external library) which uses exception. E.g.,

  Ok (make_some_call parameter)
  | (Not_found | Failure _) as e ->
    Error (error_of_exn e)
val record_trace_exn : exn -> 'a tzresult -> 'a tzresult
val trace_exn : exn -> 'b tzresult Lwt.t -> 'b tzresult Lwt.t
val generic_trace : ('a, Stdlib.Format.formatter, unit, ('berror trace) Stdlib.result Lwt.t -> ('berror trace) Stdlib.result Lwt.t) Stdlib.format4 -> 'a
val pp_exn : Stdlib.Format.formatter -> exn -> unit
val failure : ('a, Stdlib.Format.formatter, unit, error) Stdlib.format4 -> 'a
type error += Exn of exn

Wrapped OCaml/Lwt exception

type error += Canceled
val protect : ?⁠on_error:(error trace -> 'a tzresult Lwt.t) -> ?⁠canceler:Lwt_canceler.t -> (unit -> 'a tzresult Lwt.t) -> 'a tzresult Lwt.t

protect is a wrapper around Lwt.catch where the error handler operates over `trace` instead of `exn`. Besides, protect ~on_error ~canceler ~f may *cancel* f via a Lwt_canceler.t.

More precisely, protect ~on_error ~canceler f runs f (). An Lwt failure triggered by f () is wrapped into an Exn. If a canceler is given and Lwt_canceler.cancellation canceler is determined before f (), a Canceled error is returned.

Errors are caught by ~on_error (if given), otherwise the previous value is returned. An Lwt failure triggered by ~on_error is wrapped into an Exn

type error += Timeout
val with_timeout : ?⁠canceler:Lwt_canceler.t -> unit Lwt.t -> (Lwt_canceler.t -> 'a tzresult Lwt.t) -> 'a tzresult Lwt.t