From 3e11f026360d2980f18c5d7e0392b3b30bf1188e Mon Sep 17 00:00:00 2001
From: CRBroughton <crbroughton@posteo.uk>
Date: Sat, 27 Apr 2024 19:53:25 +0100
Subject: [PATCH] feat: :sparkles: Add IsNonNullish type - Check if a type is
 neither undefined or null

---
 .changeset/cyan-ducks-shout.md |  5 +++++
 README.md                      |  2 +-
 index.ts                       |  6 ++++++
 tests/IsNonNullish.test.ts     | 25 +++++++++++++++++++++++++
 tests/IsNullish.test.ts        |  6 +++---
 5 files changed, 40 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/cyan-ducks-shout.md
 create mode 100644 tests/IsNonNullish.test.ts

diff --git a/.changeset/cyan-ducks-shout.md b/.changeset/cyan-ducks-shout.md
new file mode 100644
index 0000000..5ea69f3
--- /dev/null
+++ b/.changeset/cyan-ducks-shout.md
@@ -0,0 +1,5 @@
+---
+"@crbroughton/ts-test-utils": minor
+---
+
+Add IsNonNullish type - Check if a type is neither undefined or null
diff --git a/README.md b/README.md
index 63b7443..00f72ea 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ A collection of helper TypeScript types to test other TypeScript types. This col
 - IsUndefined - Check if a type is undefined
 - IsNonUndefined - Check if a type is not undefined
 - IsNullish - Check if a type is either undefined or null
-
+- IsNonNullish - Check if a type is neither undefined or null
 ## Installation
 
 To install `ts-test-utils` with Bun, run the following command:
diff --git a/index.ts b/index.ts
index 3e0d235..b45bfcf 100644
--- a/index.ts
+++ b/index.ts
@@ -36,3 +36,9 @@ export type IsNullish<T> =
     true
     : IsUndefined<T> extends true ?
       true : false
+
+export type IsNonNullish<T> =
+  IsNullable<T> extends true ?
+    false
+    : IsUndefined<T> extends true ?
+      false : true
diff --git a/tests/IsNonNullish.test.ts b/tests/IsNonNullish.test.ts
new file mode 100644
index 0000000..4505e78
--- /dev/null
+++ b/tests/IsNonNullish.test.ts
@@ -0,0 +1,25 @@
+/* eslint-disable unused-imports/no-unused-vars */
+import { describe, it } from 'bun:test'
+import type { Expect, IsNonNullish } from '../index'
+
+describe('IsNonNullish tests', () => {
+  it('Passes the IsNonNullish test when the type is not nullish', () => {
+    type ResultNull = Expect<IsNonNullish<{ id: number }>>
+    //   ^?
+    type ResultUndefined = Expect<IsNonNullish<{ id: number }>>
+    //   ^?
+    type ResultBoth = Expect<IsNonNullish<{ id: number }>>
+    //   ^?
+  })
+  it('Failed the IsNonNullish test when the type is nullish', () => {
+    // @ts-expect-error - Fails the exclusion
+    type ResultNull = Expect<IsNonNullish<{ id: number } | null>>
+    //   ^?
+    // @ts-expect-error - Fails the exclusion
+    type ResultUndefined = Expect<IsNonNullish<{ id: number } | undefined>>
+    //   ^?
+    // @ts-expect-error - Fails the exclusion
+    type ResultBoth = Expect<IsNonNullish<{ id: number } | null | undefined>>
+    //   ^?
+  })
+})
diff --git a/tests/IsNullish.test.ts b/tests/IsNullish.test.ts
index e569aca..9927df4 100644
--- a/tests/IsNullish.test.ts
+++ b/tests/IsNullish.test.ts
@@ -2,8 +2,8 @@
 import { describe, it } from 'bun:test'
 import type { Expect, IsNullish } from '../index'
 
-describe('IsNullable tests', () => {
-  it('Passes the IsNullable test when the type is nullable', () => {
+describe('IsNullish tests', () => {
+  it('Passes the IsNullish test when the type is nullish', () => {
     type ResultNull = Expect<IsNullish<{ id: number } | null>>
     //   ^?
     type ResultUndefined = Expect<IsNullish<{ id: number } | undefined>>
@@ -11,7 +11,7 @@ describe('IsNullable tests', () => {
     type ResultBoth = Expect<IsNullish<{ id: number } | null | undefined>>
     //   ^?
   })
-  it('Failed the IsNullable test when the type is not nullable', () => {
+  it('Failed the IsNullish test when the type is not nullish', () => {
     // @ts-expect-error - Fails the exclusion
     type Result = Expect<IsNullish<{ id: string }>>
     //   ^?