From 4a193d9801122f5b616ab7c16a77df1067260372 Mon Sep 17 00:00:00 2001
From: Vitaly Budovski <vbudovski@gmail.com>
Date: Wed, 25 Dec 2024 18:39:38 +1100
Subject: [PATCH] feature: Object omit

---
 .../reference/Schema/Collections/object.mdx   | 20 +++++++++++++++++++
 paseri-lib/src/schemas/object.test.ts         | 14 +++++++++++++
 paseri-lib/src/schemas/object.ts              | 12 ++++++++++-
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/paseri-docs/src/content/docs/reference/Schema/Collections/object.mdx b/paseri-docs/src/content/docs/reference/Schema/Collections/object.mdx
index 98dd18a..fc48e03 100644
--- a/paseri-docs/src/content/docs/reference/Schema/Collections/object.mdx
+++ b/paseri-docs/src/content/docs/reference/Schema/Collections/object.mdx
@@ -154,3 +154,23 @@ p.object({
 });
 */
 ```
+
+### `omit`
+
+Analogous to TypeScript's built-in `Omit` utility type. Creates a schema that contains all except the selected keys.
+
+```typescript
+import * as p from '@vbudovski/paseri';
+
+const schema = p.object({
+    foo: p.string(),
+    bar: p.number(),
+});
+const schemaOmitted = schema.omit('foo');
+/*
+The resulting schema will be:
+p.object({
+    bar: p.number(),
+});
+*/
+```
diff --git a/paseri-lib/src/schemas/object.test.ts b/paseri-lib/src/schemas/object.test.ts
index d9b24e0..884a06f 100644
--- a/paseri-lib/src/schemas/object.test.ts
+++ b/paseri-lib/src/schemas/object.test.ts
@@ -393,3 +393,17 @@ test('Pick', () => {
         expect(result.ok).toBeTruthy();
     }
 });
+
+test('Omit', () => {
+    const schema = p.object({ foo: p.string(), bar: p.number() });
+    const schemaOmitted = schema.omit('foo');
+
+    const data = { bar: 123 };
+    const result = schemaOmitted.safeParse(data);
+    if (result.ok) {
+        expectTypeOf(result.value).toEqualTypeOf<{ bar: number }>;
+        expect(result.value).toEqual(data);
+    } else {
+        expect(result.ok).toBeTruthy();
+    }
+});
diff --git a/paseri-lib/src/schemas/object.ts b/paseri-lib/src/schemas/object.ts
index d2d813b..01cb26b 100644
--- a/paseri-lib/src/schemas/object.ts
+++ b/paseri-lib/src/schemas/object.ts
@@ -1,4 +1,4 @@
-import type { Merge, NonEmptyObject, TupleToUnion } from 'type-fest';
+import type { IsEqual, Merge, NonEmptyObject, TupleToUnion } from 'type-fest';
 import type { Infer } from '../infer.ts';
 import { type LeafNode, type TreeNode, issueCodes } from '../issue.ts';
 import { addIssue } from '../issue.ts';
@@ -184,6 +184,16 @@ class ObjectSchema<ShapeType extends ValidShapeType<ShapeType>> extends Schema<I
             Object.fromEntries(this._shape.entries().filter(([key]) => keys.includes(key as keyof ShapeType))),
         );
     }
+    omit<Keys extends [keyof ShapeType, ...(keyof ShapeType)[]]>(
+        // Ensure at least one key remains in schema.
+        ...keys: IsEqual<TupleToUnion<Keys>, keyof ShapeType> extends true ? never : Keys
+        // @ts-expect-error FIXME: How do we get the shape validation to play nicely with Omit?
+    ): ObjectSchema<Omit<ShapeType, TupleToUnion<Keys>>> {
+        // @ts-expect-error FIXME: How do we get the shape validation to play nicely with Omit?
+        return new ObjectSchema<Omit<ShapeType, TupleToUnion<Keys>>>(
+            Object.fromEntries(this._shape.entries().filter(([key]) => !keys.includes(key as keyof ShapeType))),
+        );
+    }
 }
 
 function object<ShapeType extends ValidShapeType<ShapeType>>(