From ab30d378a9ba8fdc7e0a812ab709c993902768d6 Mon Sep 17 00:00:00 2001
From: Gautier Ben Aim <benaim.gautier@gmail.com>
Date: Sat, 19 Oct 2024 14:53:58 +0200
Subject: [PATCH] feat: provide a default value to .optional()

---
 .changeset/smooth-zebras-jam.md | 5 +++++
 src/definitions.test.ts         | 1 +
 src/definitions.ts              | 7 +++++--
 3 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/smooth-zebras-jam.md

diff --git a/.changeset/smooth-zebras-jam.md b/.changeset/smooth-zebras-jam.md
new file mode 100644
index 0000000..5768bf5
--- /dev/null
+++ b/.changeset/smooth-zebras-jam.md
@@ -0,0 +1,5 @@
+---
+"formgator": patch
+---
+
+Provide a default value to `.optional()`
diff --git a/src/definitions.test.ts b/src/definitions.test.ts
index 317b27d..12ad5b3 100644
--- a/src/definitions.test.ts
+++ b/src/definitions.test.ts
@@ -106,6 +106,7 @@ describe("methods", () => {
       const data = new FormData();
 
       assert.deepEqualTyped(text().optional()[safeParse](data, "input"), succeed(undefined));
+      assert.deepEqualTyped(text().optional("")[safeParse](data, "input"), succeed(""));
     });
 
     it("should accept present fields", () => {
diff --git a/src/definitions.ts b/src/definitions.ts
index 47fcecf..f32aef1 100644
--- a/src/definitions.ts
+++ b/src/definitions.ts
@@ -58,8 +58,11 @@ export interface FormInput<T = unknown> {
    *
    * It returns `undefined` instead of `null` to differentiate between a missing
    * field (`undefined`) and a field with an empty value (`null`).
+   *
+   * You may provide a default value to be used when the field is missing.
    */
   optional(): FormInput<T | undefined>;
+  optional<U>(value: U): FormInput<T | U>;
 
   /** @private @internal */
   [safeParse]: (data: ReadonlyFormData, name: string) => Result<T, ValidationIssue>;
@@ -153,11 +156,11 @@ function refine<T, U extends T>(
   };
 }
 
-function optional<T>(this: FormInput<T>): FormInput<T | undefined> {
+function optional<T, U>(this: FormInput<T>, value?: U): FormInput<T | U> {
   return {
     ...this,
     [safeParse]: (data, name) => {
-      if (!data.has(name)) return succeed(undefined);
+      if (!data.has(name)) return succeed(value as U);
       return this[safeParse](data, name);
     },
   };