Compact field validators

CHANGES.md

@@ -2,6 +2,7 @@
 
 #### Yocaml
 
+- Add `Data.Validation.req` and `Data.Validation.opt` for compact validation and alternative name (by [xhtmlboi](https://github.com/xhtmlboi))
 - Add `Data.Validation.where_opt` (and `String`, `Int` and `Float` version) (by [xvw](https://xvw.lol))
 - Improve pretty-printing of validation errors (by [Linda-Njau](https://github.com/Linda-Njau))
 - Fix typos and improve logs display (by [clementd](https://clementd.wtf))

lib/core/data.ml

@@ -379,6 +379,32 @@ module Validation = struct
     let opt = optional assoc field validator in
     Result.bind opt (function Some x -> Ok x | None -> Ok default)
 
+  let req ?(alt = []) assoc field validation =
+    let alt_name =
+      match alt with [] -> "" | _ -> " or [" ^ String.concat ", " alt ^ "]"
+    in
+    let field_name = field ^ alt_name in
+    let rec aux = function
+      | [] -> Error (Nel.singleton @@ Missing_field { field = field_name })
+      | field :: xs -> (
+          match required assoc field validation with
+          | Ok x -> Ok x
+          | Error Nel.[ Missing_field _ ] -> aux xs
+          | Error err -> Error err)
+    in
+    aux (field :: alt)
+
+  let opt ?(alt = []) assoc field validation =
+    let rec aux = function
+      | [] -> Ok None
+      | field :: xs -> (
+          match optional assoc field validation with
+          | Ok None -> aux xs
+          | Ok x -> Ok x
+          | Error err -> Error err)
+    in
+    aux (field :: alt)
+
   let sub_record assoc validator =
     validator (mk_record assoc)
     |> Result.map_error (fun err -> Nel.singleton (Invalid_subrecord err))

lib/core/data.mli

@@ -404,6 +404,15 @@ module Validation : sig
   (** [required assoc field validator] required [field] of [assoc], validated by
       [validator]. *)
 
+  val req :
+       ?alt:string list
+    -> (string * t) list
+    -> string
+    -> (t -> 'a validated_value)
+    -> 'a validated_record
+  (** [req ?alt assoc field validator] is a compact form of {!val:required}
+      allowing alternative field names. *)
+
   val optional :
        (string * t) list
     -> string
@@ -412,6 +421,15 @@ module Validation : sig
   (** [optional assoc field validator] optional [field] of [assoc], validated by
       [validator]. *)
 
+  val opt :
+       ?alt:string list
+    -> (string * t) list
+    -> string
+    -> (t -> 'a validated_value)
+    -> 'a option validated_record
+  (** [opt ?alt assoc field validator] is a compact form of {!val:optional}
+      allowing alternative field names. *)
+
   val optional_or :
        (string * t) list
     -> string

test/e2e/run.t

@@ -314,4 +314,4 @@ Observe Residual Removing
 
 Clean the sandbox
   $ rm -r _www
-  $ rm -rf _residuals_build
+  $ rm -rf residuals_build

test/yocaml-expect/data_test.ml

@@ -0,0 +1,147 @@
+(* YOCaml a static blog generator.
+   Copyright (C) 2026 The Funkyworkers and The YOCaml's developers
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>. *)
+
+open Yocaml
+
+let my_record ?(title = "title") ?(kind = "kind") ?(description = "description")
+    ?(url = "url") () =
+  let open Data in
+  record
+    [
+      (title, string "My title")
+    ; (kind, string "My Kind")
+    ; (description, string "A description")
+    ; (url, string "https://yocaml.github.io")
+    ]
+
+let dump = function
+  | Ok x -> print_endline x
+  | Error err ->
+      Format.asprintf "%a" (Diagnostic.pp_validation_error (fun _ _ -> ())) err
+      |> print_endline
+
+let validate_my_record input =
+  let open Data.Validation in
+  record
+    (fun obj ->
+      let+ title = req obj ~alt:[ "name"; "main_title" ] "title" string
+      and+ kind = opt obj ~alt:[ "k"; "sort" ] "kind" string
+      and+ desc = req obj ~alt:[ "desc"; "synopsis" ] "description" string
+      and+ url = opt obj ~alt:[ "link"; "site" ] "url" string in
+      let open Format in
+      asprintf "%a\n\ntitle:%s\nkind:%a\ndesc:%s\nurl:%a" Data.pp input title
+        (pp_print_option pp_print_string)
+        kind desc
+        (pp_print_option pp_print_string)
+        url)
+    input
+
+let%expect_test "Validate a regular record" =
+  my_record () |> validate_my_record |> dump;
+  [%expect
+    {|
+    {"title": "My title", "kind": "My Kind", "description": "A description",
+    "url": "https://yocaml.github.io"}
+
+    title:My title
+    kind:My Kind
+    desc:A description
+    url:https://yocaml.github.io
+    |}]
+
+let%expect_test "Validate a regular record with alternative names" =
+  my_record ~title:"main_title" ~kind:"sort" ~description:"synopsis" ~url:"site"
+    ()
+  |> validate_my_record
+  |> dump;
+  [%expect
+    {|
+    {"main_title": "My title", "sort": "My Kind", "synopsis": "A description",
+    "site": "https://yocaml.github.io"}
+
+    title:My title
+    kind:My Kind
+    desc:A description
+    url:https://yocaml.github.io
+    |}]
+
+let%expect_test "Validate a regular record with missing name - 1" =
+  my_record ~title:"main_title" ~kind:"invalidfieldname" ~description:"synopsis"
+    ~url:"site" ()
+  |> validate_my_record
+  |> dump;
+  [%expect
+    {|
+    {"main_title": "My title", "invalidfieldname": "My Kind", "synopsis":
+     "A description", "site": "https://yocaml.github.io"}
+
+    title:My title
+    kind:
+    desc:A description
+    url:https://yocaml.github.io
+    |}]
+
+let%expect_test "Validate a regular record with missing name - 2" =
+  my_record ~title:"an_invalid_title_name" ~kind:"invalidfieldname"
+    ~description:"fail_because_required" ~url:"site" ()
+  |> validate_my_record
+  |> dump;
+  [%expect
+    {|
+    Invalid record:
+      Errors (2):
+      1) Missing field `title or [name, main_title]`
+
+      2) Missing field `description or [desc, synopsis]`
+
+      Given record:
+        an_invalid_title_name = `"My title"`
+        invalidfieldname = `"My Kind"`
+        fail_because_required = `"A description"`
+        site = `"https://yocaml.github.io"`
+    |}]
+
+let%expect_test "Validate a regular record with invalid fields" =
+  Data.(
+    record
+      [
+        ("title", list_of string [])
+      ; ("sort", string "My Kind")
+      ; ("desc", string "A description")
+      ; ("link", int 42)
+      ])
+  |> validate_my_record
+  |> dump;
+  [%expect
+    {|
+    Invalid record:
+      Errors (2):
+      1) Invalid field `title`:
+           Invalid shape:
+             Expected: strict-string
+             Given: `[]`
+
+      2) Invalid field `link`:
+           Invalid shape:
+             Expected: strict-string
+             Given: `42`
+
+      Given record:
+        title = `[]`
+        sort = `"My Kind"`
+        desc = `"A description"`
+        link = `42`
+    |}]