make a new package for helpers

packages/helpers/prune-nullish-values.test.ts

@@ -0,0 +1,35 @@
+import { expect, test } from "vitest"
+import type { PruneNullishValues } from "./prune-nullish-values"
+import { pruneNullishValues } from "./prune-nullish-values"
+
+test("pruneNullishValues", () => {
+  type InputType = {
+    a: string
+    b: string | null | undefined
+    c?: string
+    d: {
+      a: string
+      b: string | undefined
+    }
+  }
+
+  const input: InputType = {
+    a: "a",
+    // eslint-disable-next-line unicorn/no-null
+    b: null,
+    c: undefined,
+    d: {
+      a: "a",
+      b: undefined,
+    },
+  }
+
+  const output: PruneNullishValues<InputType> = {
+    a: "a",
+    d: {
+      a: "a",
+    },
+  }
+
+  expect(pruneNullishValues(input)).toEqual(output)
+})