ProvenPin Install

defu and klona deep defaults with safe cloning: working versions (tested 2026-10-16)

Deep-merge layered configuration defaults with defu (arrays concatenate or replace via a custom merger) and clone with klona so mutations never touch the source, fully offline.

passed4 passed · 0 failed2026-10-16 15:20 UTC
Status
passed
Last passed
2026-10-16 15:20 UTC
Tests
4 / 4
Language
TypeScript
Runtime
node v22.23.3
pinned versions4
defu@6.1.7klona@2.0.6@types/node@26.6.5tsx@4.23.15
run it
npm install --no-audit --no-fund --ignore-scripts=false
npm test
test environment
node v22.23.3
linux 6.17.0-1022-azure
x64
runner: github-actions 38923127324

The code

Exactly the files that passed. Your agent can pull them with get_recipe("defu-klona-merge") (install), or see them on GitHub.

package.json
{
  "name": "defu-klona-merge",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --import tsx --test test/*.test.ts"
  },
  "dependencies": {
    "defu": "6.1.7",
    "klona": "2.0.6"
  },
  "devDependencies": {
    "@types/node": "26.6.5",
    "tsx": "4.23.15"
  }
}
src/config.ts
import { defu, createDefu } from "defu";
import { klona } from "klona";

export type Config = {
  host: string;
  port: number;
  retries: number;
  features: string[];
  tls: { enabled: boolean; cert?: string };
};

export const defaults: Config = {
  host: "localhost",
  port: 5432,
  retries: 3,
  features: ["base"],
  tls: { enabled: false },
};

export function mergeConfig(overrides: Partial<Config>): Config {
  return defu(overrides, defaults) as Config;
}

export const defuReplaceArrays = createDefu((obj, key, value) => {
  if (Array.isArray(obj[key]) || Array.isArray(value)) {
    obj[key] = value;
    return true;
  }
  return false;
});

export function mergeConfigReplaceArrays(overrides: Partial<Config>): Config {
  return defuReplaceArrays(overrides, defaults) as Config;
}

export function cloneConfig(config: Config): Config {
  return klona(config);
}
test/config.test.ts
import { test } from "node:test";
import assert from "node:assert/strict";
import {
  mergeConfig,
  mergeConfigReplaceArrays,
  cloneConfig,
} from "../src/config.ts";

test("applies nested defaults", () => {
  const config = mergeConfig({ port: 8080, tls: { enabled: true } });
  assert.equal(config.port, 8080);
  assert.equal(config.host, "localhost");
  assert.equal(config.retries, 3);
  assert.equal(config.tls.enabled, true);
  assert.deepEqual(config.features, ["base"]);
});

test("concatenates arrays by default", () => {
  const config = mergeConfig({ features: ["custom"] });
  assert.deepEqual(config.features, ["custom", "base"]);
});

test("replaces arrays with a custom defu merger", () => {
  const config = mergeConfigReplaceArrays({ features: ["custom"] });
  assert.deepEqual(config.features, ["custom"]);
});

test("klona clone is independent from the merged source", () => {
  const merged = mergeConfig({ features: ["custom"], tls: { enabled: true } });
  const copy = cloneConfig(merged);
  assert.notEqual(copy, merged);
  assert.notEqual(copy.tls, merged.tls);
  copy.features.push("extra");
  copy.tls.enabled = false;
  assert.deepEqual(merged.features, ["custom", "base"]);
  assert.equal(merged.tls.enabled, true);
});

Connect to ProvenPin

Add the free MCP server so your agent can pull this recipe and others like it. Same setup as the docs.

terminal
claude mcp add --transport http provenpin https://mcp.provenpin.com/mcp

Any other MCP client: Streamable HTTP at https://mcp.provenpin.com/mcp. No API key, no signup.