svelte-kit-vice/src/arts/sium/test/lazy.test.ts

import { describe, expect, it } from 'vitest';
import { array, lazy, object, optional, string } from '../core';
import { createSchema } from '../core/schema';
import type { Schema } from '../core/types';
import { SiumAsyncSchemaError, SiumLazyResolvingError } from '../errors';

type TreeNode = {
	value: string;
	children?: TreeNode[];
};

type Alpha = {
	name: string;
	beta?: Beta;
};

type Beta = {
	label: string;
	alpha?: Alpha;
};

describe('lazy()', () => {
	it('delegates primitive decode/encode through the cached schema', () => {
		const schema = lazy(() => string());

		expect(schema.decodeSync('x')).toBe('x');
		expect(schema.encode('x')).toBe('x');
	});

	it('decodes self-referential trees to arbitrary input depth', () => {
		const TreeSchema: Schema<TreeNode, TreeNode> = lazy(() =>
			object({
				value: string(),
				children: optional(array(TreeSchema))
			})
		);

		const tree = TreeSchema.decodeSync({
			value: 'root',
			children: [
				{
					value: 'branch',
					children: [{ value: 'leaf' }]
				}
			]
		});

		expect(tree).toEqual({
			value: 'root',
			children: [
				{
					value: 'branch',
					children: [{ value: 'leaf', children: undefined }]
				}
			]
		});
	});

	it('supports mutual recursion through lazy forward references', () => {
		const AlphaSchema: Schema<Alpha, Alpha> = lazy(() =>
			object({
				name: string(),
				beta: optional(BetaSchema)
			})
		);
		const BetaSchema: Schema<Beta, Beta> = lazy(() =>
			object({
				label: string(),
				alpha: optional(AlphaSchema)
			})
		);

		expect(
			AlphaSchema.decodeSync({
				name: 'a1',
				beta: {
					label: 'b1',
					alpha: {
						name: 'a2'
					}
				}
			})
		).toEqual({
			name: 'a1',
			beta: {
				label: 'b1',
				alpha: {
					name: 'a2',
					beta: undefined
				}
			}
		});
	});

	it('round-trips recursive trees through decode + encode', () => {
		const TreeSchema: Schema<TreeNode, TreeNode> = lazy(() =>
			object({
				value: string(),
				children: optional(array(TreeSchema))
			})
		);
		const input = {
			value: 'root',
			children: [{ value: 'leaf' }]
		};

		expect(TreeSchema.encode(TreeSchema.decodeSync(input))).toEqual({
			value: 'root',
			children: [
				{
					value: 'leaf',
					children: undefined
				}
			]
		});
	});

	it('inherits async from the resolved inner schema', () => {
		const schema = lazy(() =>
			createSchema({
				kind: 'string',
				async: true,
				decodeImpl: async (input: string) => input,
				encode: (value: string) => value
			})
		);

		expect(schema['~sium'].async).toBe(true);
	});

	it('reports the inner kind transparently after resolution', () => {
		const schema = lazy(() => string());

		expect(schema['~sium'].kind).toBe('string');
	});

	it('passes through the inner shape transparently after resolution', () => {
		const inner = object({ value: string() });
		const schema = lazy(() => inner);

		expect(schema['~sium'].shape).toBe(inner['~sium'].shape);
	});

	it('invokes the factory thunk once and caches the resolved schema', async () => {
		let calls = 0;
		const schema = lazy(() => {
			calls += 1;
			return string();
		});

		expect(schema.decodeSync('a')).toBe('a');
		expect(schema.encode('b')).toBe('b');
		await expect(schema.validate('c')).resolves.toEqual({ ok: true, value: 'c' });
		expect(schema['~sium'].kind).toBe('string');
		expect(calls).toBe(1);
	});

	it('delegates the Standard Schema contract to the resolved inner schema', async () => {
		const schema = lazy(() => string());

		expect(schema['~standard'].version).toBe(1);
		expect(schema['~standard'].vendor).toBe('sium');
		await expect(schema['~standard'].validate('ok')).resolves.toEqual({ value: 'ok' });
	});

	it('preserves validation issue paths from recursive objects', async () => {
		const TreeSchema: Schema<TreeNode, TreeNode> = lazy(() =>
			object({
				value: string(),
				children: optional(array(TreeSchema))
			})
		);

		await expect(
			TreeSchema.validate({
				value: 42 as never,
				children: [{ value: 'leaf' }]
			})
		).resolves.toEqual({
			ok: false,
			issues: [
				{
					path: ['value'],
					code: 'type',
					message: '#?sium.errors.type|Expected {{expected}} but received {{actual}}',
					params: {
						expected: 'string',
						actual: 'number'
					}
				}
			]
		});
	});

	it('resolves recursion based on the input shape rather than schema depth', () => {
		const TreeSchema: Schema<TreeNode, TreeNode> = lazy(() =>
			object({
				value: string(),
				children: optional(array(TreeSchema))
			})
		);

		expect(TreeSchema.decodeSync({ value: 'leaf' })).toEqual({
			value: 'leaf',
			children: undefined
		});
	});

	it('rethrows SiumAsyncSchemaError from decodeSync when the inner schema is async', () => {
		const schema = lazy(() =>
			createSchema({
				kind: 'string',
				async: true,
				decodeImpl: async (input: string) => input,
				encode: (value: string) => value
			})
		);

		expect(() => schema.decodeSync('x')).toThrow(SiumAsyncSchemaError);
	});

	it('throws SiumLazyResolvingError when the thunk uses the proxy while resolving', () => {
		const schema: Schema<string, string> = lazy(() => {
			schema.decodeSync('x');
			return string();
		});

		expect(() => schema.decodeSync('x')).toThrow(SiumLazyResolvingError);
	});

	it('throws SiumLazyResolvingError when the thunk returns the same lazy proxy', () => {
		const schema: Schema<string, string> = lazy(() => schema);

		expect(() => schema.decodeSync('x')).toThrow(SiumLazyResolvingError);
	});

	it('is re-exported by the core barrel', () => {
		expect(lazy).toBeTypeOf('function');
	});
});