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_inline fields][@@@end]

      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) Pervasives.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