Merge pull request #57 from lambdalisue/impl-objmodify

👍 Add `isObjectOf` modify functions (`isReadonlyOf`, `isStrictOf`, `isRequiredOf`, `isPartialOf`, `isPickOf`, and `isOmitOf`)

Author: lambdalisue

README.md

@@ -31,8 +31,7 @@ if (is.String(a)) {
 }
 ```
 
-Additionally, `is*Of` (or `is.*Of`) functions return type predicate functions to
-predicate types of `x` more precisely like:
+For more complex types, you can use `is*Of` (or `is.*Of`) functions like:
 
 ```typescript
 import {
@@ -44,16 +43,19 @@ const isArticle = is.ObjectOf({
   title: is.String,
   body: is.String,
   refs: is.ArrayOf(
-    is.OneOf([
+    is.UnionOf([
       is.String,
       is.ObjectOf({
         name: is.String,
         url: is.String,
       }),
     ]),
   ),
+  createTime: is.OptionalOf(is.InstanceOf(Date)),
+  updateTime: is.OptionalOf(is.InstanceOf(Date)),
 });
 
+// Infer the type of `Article` from the definition of `isArticle`
 type Article = PredicateType<typeof isArticle>;
 
 const a: unknown = {
@@ -76,6 +78,114 @@ if (isArticle(a)) {
 }
 ```
 
+Additionally, you can manipulate the predicate function returned from
+`isObjectOf` with `isPickOf`, `isOmitOf`, `isPartialOf`, and `isRequiredOf`
+similar to TypeScript's `Pick`, `Omit`, `Partial`, `Required` utility types.
+
+```typescript
+import { is } from "https://deno.land/x/unknownutil@$MODULE_VERSION/mod.ts";
+
+const isArticle = is.ObjectOf({
+  title: is.String,
+  body: is.String,
+  refs: is.ArrayOf(
+    is.UnionOf([
+      is.String,
+      is.ObjectOf({
+        name: is.String,
+        url: is.String,
+      }),
+    ]),
+  ),
+  createTime: is.OptionalOf(is.InstanceOf(Date)),
+  updateTime: is.OptionalOf(is.InstanceOf(Date)),
+});
+
+const isArticleCreateParams = is.PickOf(isArticle, ["title", "body", "refs"]);
+// is equivalent to
+//const isArticleCreateParams = is.ObjectOf({
+//  title: is.String,
+//  body: is.String,
+//  refs: is.ArrayOf(
+//    is.UnionOf([
+//      is.String,
+//      is.ObjectOf({
+//        name: is.String,
+//        url: is.String,
+//      }),
+//    ]),
+//  ),
+//});
+
+const isArticleUpdateParams = is.OmitOf(isArticleCreateParams, ["title"]);
+// is equivalent to
+//const isArticleUpdateParams = is.ObjectOf({
+//  body: is.String,
+//  refs: is.ArrayOf(
+//    is.UnionOf([
+//      is.String,
+//      is.ObjectOf({
+//        name: is.String,
+//        url: is.String,
+//      }),
+//    ]),
+//  ),
+//});
+
+const isArticlePatchParams = is.PartialOf(isArticleUpdateParams);
+// is equivalent to
+//const isArticlePatchParams = is.ObjectOf({
+//  body: is.OptionalOf(is.String),
+//  refs: is.OptionalOf(is.ArrayOf(
+//    is.UnionOf([
+//      is.String,
+//      is.ObjectOf({
+//        name: is.String,
+//        url: is.String,
+//      }),
+//    ]),
+//  )),
+//});
+
+const isArticleAvailableParams = is.RequiredOf(isArticle);
+// is equivalent to
+//const isArticlePutParams = is.ObjectOf({
+//  body: is.String,
+//  refs: is.ArrayOf(
+//    is.UnionOf([
+//      is.String,
+//      is.ObjectOf({
+//        name: is.String,
+//        url: is.String,
+//      }),
+//    ]),
+//  ),
+//  createTime: is.InstanceOf(Date),
+//  updateTime: is.InstanceOf(Date),
+//});
+```
+
+If you need an union type or an intersection type, use `isUnionOf` and
+`isIntersectionOf` like:
+
+```typescript
+import { is } from "https://deno.land/x/unknownutil@$MODULE_VERSION/mod.ts";
+
+const isFoo = is.ObjectOf({
+  foo: is.String,
+});
+
+const isBar = is.ObjectOf({
+  bar: is.String,
+});
+
+const isFooOrBar = is.UnionOf([isFoo, isBar]);
+// { foo: string } | { bar: string }
+
+const isFooAndBar = is.IntersectionOf([isFoo, isBar]);
+// { foo: string } & { bar: string }
+```
+
 ### assert
 
 The `assert` function does nothing if a given value is expected type. Otherwise,

_typeutil.ts

@@ -0,0 +1,10 @@
+export type FlatType<T> = T extends Record<PropertyKey, unknown>
+  ? { [K in keyof T]: FlatType<T[K]> }
+  : T;
+
+export type UnionToIntersection<U> =
+  (U extends unknown ? (k: U) => void : never) extends ((k: infer I) => void)
+    ? I
+    : never;
+
+export type Writable<T> = { -readonly [P in keyof T]: T[P] };