feat: zod-lite

Author: JoshuaKGoldberg

projects/type-operations/zod-lite/README.md

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+# Zod Lite
+
+> A [Learning TypeScript > Type Operations](https://learning-typescript.com/type-operations) 🍲 entree project.
+
+Kneel before Zod!
+
+## Setup
+
+In one terminal, run the TypeScript compiler via the `tsc` script.
+For example, to start the TypeScript compiler in watch mode:
+
+```shell
+npm run tsc -- --watch
+```
+
+In another terminal, run Jest via the `test` script.
+For example, to start tests in watch mode:
+
+```shell
+npm run test -- --watch
+```
+
+## Specification
+
+Create and export the following functions from `src/index.ts`:
+
+- `string()`: creates a schema object representing any primitive string
+- `literal<Value>(value)`: creates a schema object of a literal string value
+- `union<Values>(values)`: creates a schema object representing multiple allowed type constituents
+- `object<Properties>(properties)`: creates a schema object representing an object
+
+Additionally, export an `type Infer<Schema>` that creates a TypeScript type for a schema.
+
+## Example
+
+This code:
+
+```ts
+import * as z from "./index";
+
+const spySchema = z.object({
+	disguise: z.string(),
+	moniker: z.literal("007"),
+	plan: z.union([z.literal("active"), z.literal("improvising")]),
+});
+
+type Spy = z.Infer<typeof spySchema>;
+```
+
+...create a `Spy` type equivalent to:
+
+```ts
+type Spy = {
+	disguise: string;
+	moniker: "007";
+	plan: "active" | "improvising";
+};
+```

projects/type-operations/zod-lite/_category_.json

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+{
+	"label": "🍲 Zod Lite",
+	"position": 3
+}

projects/type-operations/zod-lite/jest.config.js

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+module.exports = {
+	transform: {
+		"^.+\\.(t|j)sx?$": [
+			"@swc/jest",
+			{
+				jsc: {
+					target: "es2021",
+				},
+			},
+		],
+	},
+};

projects/type-operations/zod-lite/package.json

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+{
+	"name": "the-narrow-trail",
+	"scripts": {
+		"test": "jest",
+		"test:solutions": "cross-env TEST_SOLUTIONS=1 jest",
+		"tsc": "tsc"
+	}
+}

projects/type-operations/zod-lite/src/index.test.ts

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+import { describe, jest, test } from "@jest/globals";
+import { expectType } from "tsd";
+
+import * as index from "./index";
+import * as solution from "./solution";
+
+const z = process.env.TEST_SOLUTIONS ? solution : index;
+
+const mockRandom = jest.spyOn(Math, "random");
+
+describe("zod-lite", () => {
+	test("Spy", () => {
+		const spySchema = z.object({
+			disguise: z.string(),
+			moniker: z.literal("007"),
+			plan: z.union([z.literal("active"), z.literal("improvising")]),
+		});
+		expectType<{
+			disguise: string;
+			moniker: "007";
+			plan: "active" | "improvising";
+		}>({} as index.Infer<typeof spySchema>);
+	});
+});

projects/type-operations/zod-lite/src/index.ts

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+// Write your functions and type here! ✨
+// You'll need to export them so the tests can use them.

projects/type-operations/zod-lite/src/solution.ts

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+// Primitives
+
+export interface SchemaString {
+	primitive: "string";
+	zType: "primitive";
+}
+
+export const string = (): SchemaString => ({
+	primitive: "string",
+	zType: "primitive",
+});
+
+// Literals
+export interface SchemaLiteral<Value> {
+	value: Value;
+	zType: "literal";
+}
+
+export const literal = <Value extends string>(
+	value: Value
+): SchemaLiteral<Value> => ({
+	value,
+	zType: "literal",
+});
+
+// Unions
+export interface SchemaUnion<Values extends any[]> {
+	values: Values;
+	zType: "union";
+}
+
+export const union = <Values extends any[]>(
+	values: Values
+): SchemaUnion<Values> => ({
+	values,
+	zType: "union",
+});
+
+export type UnwrapSchemaUnion<Values> = Values extends (infer Value)[]
+	? Infer<Value>
+	: never;
+
+// Objects
+export interface SchemaObject<Properties> {
+	properties: Properties;
+	zType: "object";
+}
+
+export const object = <Properties>(
+	properties: Properties
+): SchemaObject<Properties> => ({
+	properties,
+	zType: "object",
+});
+
+export type UnwrapSchemaObject<Properties> = {
+	[K in keyof Properties]: Infer<Properties[K]>;
+};
+
+export type Infer<Schema> =
+	// Primitives (string)
+	Schema extends SchemaString
+		? string
+		: // Literals
+		Schema extends SchemaLiteral<infer Value>
+		? Value
+		: // Unions
+		Schema extends SchemaUnion<infer Values>
+		? UnwrapSchemaUnion<Values>
+		: // Objects
+		Schema extends SchemaObject<infer Properties>
+		? UnwrapSchemaObject<Properties>
+		: never;

projects/type-operations/zod-lite/tsconfig.json

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+{
+	"extends": "../../../tsconfig.json",
+	"include": ["src"]
+}