From 16e27384a51d946b604b1c3fac84ce025ed9897e Mon Sep 17 00:00:00 2001
From: Lexus Drumgold <unicornware@flexdevelopment.llc>
Date: Tue, 23 May 2023 20:23:20 -0400
Subject: [PATCH] feat(types): `IsRequiredKey`, `IfRequiredKey`

Signed-off-by: Lexus Drumgold <unicornware@flexdevelopment.llc>
---
 src/types/__tests__/if-key-required.spec-d.ts | 28 +++++++++++++++++++
 src/types/__tests__/is-key-required.spec-d.ts | 25 +++++++++++++++++
 src/types/if-key-required.ts                  | 27 ++++++++++++++++++
 src/types/index.ts                            |  2 ++
 src/types/is-key-required.ts                  | 19 +++++++++++++
 src/types/keys-required.ts                    |  8 ++----
 6 files changed, 103 insertions(+), 6 deletions(-)
 create mode 100644 src/types/__tests__/if-key-required.spec-d.ts
 create mode 100644 src/types/__tests__/is-key-required.spec-d.ts
 create mode 100644 src/types/if-key-required.ts
 create mode 100644 src/types/is-key-required.ts

diff --git a/src/types/__tests__/if-key-required.spec-d.ts b/src/types/__tests__/if-key-required.spec-d.ts
new file mode 100644
index 00000000..e5057223
--- /dev/null
+++ b/src/types/__tests__/if-key-required.spec-d.ts
@@ -0,0 +1,28 @@
+/**
+ * @file Type Tests - IfRequiredKey
+ * @module tutils/types/tests/unit-d/IfRequiredKey
+ */
+
+import type Author from '#fixtures/author.interface'
+import type TestSubject from '../if-key-required'
+
+describe('unit-d:types/IfRequiredKey', () => {
+  type False = false
+  type True = true
+
+  it('should equal False if IsRequiredKey<T, K> extends false', () => {
+    // Arrange
+    type K = 'email'
+
+    // Expect
+    expectTypeOf<TestSubject<Author, K, True, False>>().toEqualTypeOf<False>()
+  })
+
+  it('should equal True if IsRequiredKey<T, K> extends true', () => {
+    // Arrange
+    type K = 'first_name'
+
+    // Expect
+    expectTypeOf<TestSubject<Author, K, True, False>>().toEqualTypeOf<True>()
+  })
+})
diff --git a/src/types/__tests__/is-key-required.spec-d.ts b/src/types/__tests__/is-key-required.spec-d.ts
new file mode 100644
index 00000000..cced57a2
--- /dev/null
+++ b/src/types/__tests__/is-key-required.spec-d.ts
@@ -0,0 +1,25 @@
+/**
+ * @file Type Tests - IsRequiredKey
+ * @module tutils/types/tests/unit-d/IsRequiredKey
+ */
+
+import type Author from '#fixtures/author.interface'
+import type TestSubject from '../is-key-required'
+
+describe('unit-d:types/IsRequiredKey', () => {
+  it('should equal false if K is not required property of T', () => {
+    // Arrange
+    type K = 'email'
+
+    // Expect
+    expectTypeOf<TestSubject<Author, K>>().toEqualTypeOf<false>()
+  })
+
+  it('should equal true if K is required property of T', () => {
+    // Arrange
+    type K = 'last_name'
+
+    // Expect
+    expectTypeOf<TestSubject<Author, K>>().toEqualTypeOf<true>()
+  })
+})
diff --git a/src/types/if-key-required.ts b/src/types/if-key-required.ts
new file mode 100644
index 00000000..d45390d6
--- /dev/null
+++ b/src/types/if-key-required.ts
@@ -0,0 +1,27 @@
+/**
+ * @file Type Definitions - IfRequiredKey
+ * @module tutils/types/IfRequiredKey
+ */
+
+import type IndexSignature from './index-signature'
+import type IsRequiredKey from './is-key-required'
+
+/**
+ * Conditional type that resolves depending on whether or not `K` is a required
+ * property of `T`.
+ *
+ * @see {@linkcode IsRequiredKey}
+ *
+ * @template T - Type to evaluate
+ * @template K - Key to evaluate
+ * @template True - Type if `K` is required property
+ * @template False - Type if `K` is not required property
+ */
+type IfRequiredKey<T, K extends IndexSignature, True, False> = IsRequiredKey<
+  T,
+  K
+> extends true
+  ? True
+  : False
+
+export type { IfRequiredKey as default }
diff --git a/src/types/index.ts b/src/types/index.ts
index 11b88c8a..8db5503e 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -35,6 +35,7 @@ export type { default as IfFunction } from './if-function'
 export type { default as IfJsonPrimitive } from './if-json-primitive'
 export type { default as IfOptionalKey } from './if-key-optional'
 export type { default as IfExactOptionalKey } from './if-key-optional-exact'
+export type { default as IfRequiredKey } from './if-key-required'
 export type { default as IfNever } from './if-never'
 export type { default as IfNil } from './if-nil'
 export type { default as IfNull } from './if-null'
@@ -58,6 +59,7 @@ export type { default as IsFunction } from './is-function'
 export type { default as IsJsonPrimitive } from './is-json-primitive'
 export type { default as IsOptionalKey } from './is-key-optional'
 export type { default as IsExactOptionalKey } from './is-key-optional-exact'
+export type { default as IsRequiredKey } from './is-key-required'
 export type { default as IsNever } from './is-never'
 export type { default as IsNil } from './is-nil'
 export type { default as IsNull } from './is-null'
diff --git a/src/types/is-key-required.ts b/src/types/is-key-required.ts
new file mode 100644
index 00000000..2291c0df
--- /dev/null
+++ b/src/types/is-key-required.ts
@@ -0,0 +1,19 @@
+/**
+ * @file Type Definitions - IsRequiredKey
+ * @module tutils/types/IsRequiredKey
+ */
+
+import type IndexSignature from './index-signature'
+import type RequiredKeys from './keys-required'
+
+/**
+ * Returns a boolean indicating if `K` is a required property of `T`.
+ *
+ * @template T - Type to evaluate
+ * @template K - Key to evaluate
+ */
+type IsRequiredKey<T, K extends IndexSignature> = K extends RequiredKeys<T>
+  ? true
+  : false
+
+export type { IsRequiredKey as default }
diff --git a/src/types/keys-required.ts b/src/types/keys-required.ts
index 3a97cb30..2ddfbfe4 100644
--- a/src/types/keys-required.ts
+++ b/src/types/keys-required.ts
@@ -3,16 +3,12 @@
  * @module tutils/types/RequiredKeys
  */
 
-import type ObjectPlain from './object-plain'
-
 /**
  * Extracts all required keys from `T`.
  *
- * @todo support nested keys
- *
- * @template T - Object type to evaluate
+ * @template T - Type to evaluate
  */
-type RequiredKeys<T extends ObjectPlain> = Exclude<
+type RequiredKeys<T> = Exclude<
   { [K in keyof T]: T extends Record<K, T[K]> ? K : never }[keyof T],
   undefined
 >