Module Base.Validate

A module for organizing validations of data structures.

Allows standardized ways of checking for conditions, and keeps track of the location of errors by keeping a path to each error found. Thus, if you were validating the following datastructure:

{ foo = 3;
  bar = { snoo = 34.5;
          blue = Snoot -6; }
}

One might end up with an error with the error path:

bar.blue.Snoot : value -6 <= bound 0

By convention, the validations for a type defined in module M appear in module M, and have their name prefixed by validate_. E.g., Int.validate_positive.

Here's an example of how you would use validate with a record:

type t =
  { foo: int;
    bar: float;
  }
[@@deriving fields]

let validate t =
  let module V = Validate in
  let w check = V.field_folder t check in
  V.of_list
    (Fields.fold ~init:[]
       ~foo:(w Int.validate_positive)
       ~bar:(w Float.validate_non_negative)
    )

And here's an example of how you would use it with a variant type:

type t =
  | Foo of int
  | Bar of (float * int)
  | Snoo of Floogle.t

let validate = function
  | Foo i -> V.name "Foo" (Int.validate_positive i)
  | Bar p -> V.name "Bar" (V.pair
                             ~fst:Float.validate_positive
                             ~snd:Int.validate_non_negative p)
  | Snoo floogle -> V.name "Snoo" (Floogle.validate floogle)
type t

The result of a validation. This effectively contains the list of errors, qualified by their location path

type 'a check = 'a -> t

To make function signatures easier to read.

val pass : t

A result containing no errors.

val fail : string -> t

A result containing a single error.

val fails : string -> 'a -> ('a -> Sexp.t) -> t
val fail_s : Sexp.t -> t

This can be used with the %sexp extension.

val failf : ('a, unit, string, t) format4 -> 'a

Like sprintf or failwithf but produces a t instead of a string or exception.

val combine : t -> t -> t
val of_list : t list -> t

Combines multiple results, merging errors.

val name : string -> t -> t

Extends location path by one name.

val name_list : string -> t list -> t
val fail_fn : string -> _ check

fail_fn err returns a function that always returns fail, with err as the error message. (Note that there is no pass_fn so as to discourage people from ignoring the type of the value being passed unconditionally irrespective of type.)

val pass_bool : bool check

Checks for unconditionally passing a bool.

val pass_unit : unit check

Checks for unconditionally passing a unit.

val protect : 'a check -> 'a check

protect f x applies the validation f to x, catching any exceptions and returning them as errors.

val try_with : (unit -> unit) -> t

try_with f runs f catching any exceptions and returning them as errors.

val result : t -> unit Or_error.t
val errors : t -> string list

Returns a list of formatted error strings, which include both the error message and the path to the error.

val maybe_raise : t -> unit

If the result contains any errors, then raises an exception with a formatted error message containing a message for every error.

val valid_or_error : 'a -> 'a check -> 'a Or_error.t

Returns an error if validation fails.

val field : 'record -> ([> `Read ], 'record, 'a) Field.t_with_perm -> 'a check -> t

Used for validating an individual field.

val field_folder : 'record -> 'a check -> t list -> ([> `Read ], 'record, 'a) Field.t_with_perm -> t list

Creates a function for use in a Fields.fold.

val field_direct_folder : 'a check -> (t list -> ([> `Read ], 'record, 'a) Field.t_with_perm -> 'record -> 'a -> t list) Staged.t

Creates a function for use in a Fields.Direct.fold.

val all : 'a check list -> 'a check

Combines a list of validation functions into one that does all validations.

val of_result : ('a -> (unit, string) Result.t) -> 'a check

Creates a validation function from a function that produces a Result.t.

val of_error : ('a -> unit Or_error.t) -> 'a check
val booltest : ('a -> bool) -> if_false:string -> 'a check

Creates a validation function from a function that produces a bool.

val pair : fst:'a check -> snd:'b check -> ('a * 'b) check

Validation functions for particular data types.

val list_indexed : 'a check -> 'a list check

Validates a list, naming each element by its position in the list (where the first position is 1, not 0).

val list : name:('a -> string) -> 'a check -> 'a list check

Validates a list, naming each element using a user-defined function for computing the name.

val first_failure : t -> t -> t
val of_error_opt : string option -> t
val alist : name:('a -> string) -> 'b check -> ('a * 'b) list check

Validates an association list, naming each element using a user-defined function for computing the name.

val bounded : name:('a -> string) -> lower:'a Maybe_bound.t -> upper:'a Maybe_bound.t -> compare:('a -> 'a -> int) -> 'a check
module Infix : sig ... end