@eslint/object-schema 2.1.7: MergeStrategy

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify @eslint/object-schema.MergeStrategy in pkg:npm/%40eslint/object-schema@2.1.7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40eslint/object-schema@2.1.7
Demonstrate these symbols/APIs:
  - @eslint/object-schema.MergeStrategy

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:aa6ac302a8136fd7d270af86585186f8c48867ad2b96f1b34c2f57eb5b5c60ae","contract":["MergeStrategy.overwrite unconditionally returns the second value over the first value","MergeStrategy.replace returns the second value if defined, otherwise preserving the first value","MergeStrategy.assign returns a newly created object combining properties from both values without mutating inputs","ObjectSchema correctly merges object properties using MergeStrategy string identifiers overwrite, replace, and assign","ObjectSchema accepts MergeStrategy static methods as direct function merge handlers for multi-object merges"],"goal":"verify @eslint/object-schema.MergeStrategy in pkg:npm/%40eslint/object-schema@2.1.7","kind":"HOW","packages":["pkg:npm/%40eslint/object-schema@2.1.7"],"schemaVersion":1,"symbols":["@eslint/object-schema.MergeStrategy"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40eslint/object-schema@2.1.7"],"schemaVersion":1,"subject":"pkg:npm/%40eslint/object-schema@2.1.7","symbols":["@eslint/object-schema.MergeStrategy"],"verifierAdapter":"node-typescript@1"}

import { MergeStrategy, ObjectSchema } from "@eslint/object-schema";

export function mergeObjectsWithStrategy(schemaDefinition, ...objects) {
  const schema = new ObjectSchema(schemaDefinition);
  return schema.merge(...objects);
}

export { MergeStrategy, ObjectSchema };

{
  "name": "sample-eslint-merge-strategy",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-eslint-merge-strategy",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "@eslint/object-schema": "2.1.7"
      }
    },
    "node_modules/@eslint/object-schema": {
      "version": "2.1.7",
      "resolved": "https://registry.npmjs.org/@eslint/object-schema/-/object-schema-2.1.7.tgz",
      "integrity": "sha512-VtAOaymWVfZcmZbp6E2mympDIHvyjXs/12LqWYjVw6qjrfF+VK+fyG33kChz3nnK+SU5/NeHOqrTEHS8sXO3OA==",
      "license": "Apache-2.0",
      "engines": {
        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
      }
    }
  }
}

{
  "name": "sample-eslint-merge-strategy",
  "version": "1.0.0",
  "license": "MIT-0",
  "type": "module",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "@eslint/object-schema": "2.1.7"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @eslint/object-schema.MergeStrategy in pkg:npm/%40eslint/object-schema@2.1.7",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40eslint/object-schema@2.1.7"
  ],
  "symbols": [
    "@eslint/object-schema.MergeStrategy"
  ]
}

import assert from "node:assert/strict";
import { MergeStrategy, ObjectSchema } from "@eslint/object-schema";

// 1. MergeStrategy.overwrite unconditionally returns the second value over the first value
assert.equal(MergeStrategy.overwrite("initial", "overwritten"), "overwritten");
assert.equal(MergeStrategy.overwrite(100, 200), 200);
assert.equal(MergeStrategy.overwrite(true, false), false);
assert.equal(MergeStrategy.overwrite("exists", undefined), undefined);
assert.equal(MergeStrategy.overwrite("exists", null), null);

const objA = { key: "a" };
const objB = { key: "b" };
assert.equal(MergeStrategy.overwrite(objA, objB), objB);

// 2. MergeStrategy.replace returns the second value if defined, otherwise preserving the first value
assert.equal(MergeStrategy.replace("keep-me", undefined), "keep-me");
assert.equal(MergeStrategy.replace(42, undefined), 42);
assert.equal(MergeStrategy.replace(false, undefined), false);
assert.equal(MergeStrategy.replace(null, undefined), null);

assert.equal(MergeStrategy.replace("old", "new"), "new");
assert.equal(MergeStrategy.replace("old", null), null);
assert.equal(MergeStrategy.replace("old", false), false);
assert.equal(MergeStrategy.replace("old", 0), 0);
assert.equal(MergeStrategy.replace("old", ""), "");

// 3. MergeStrategy.assign returns a newly created object combining properties from both values without mutating inputs
const source1 = { a: 1, b: 2 };
const source2 = { b: 20, c: 30 };
const assigned = MergeStrategy.assign(source1, source2);

assert.deepEqual(assigned, { a: 1, b: 20, c: 30 });
assert.notEqual(assigned, source1);
assert.notEqual(assigned, source2);
assert.deepEqual(source1, { a: 1, b: 2 });
assert.deepEqual(source2, { b: 20, c: 30 });

assert.deepEqual(MergeStrategy.assign({ x: 10 }, undefined), { x: 10 });
assert.deepEqual(MergeStrategy.assign({ x: 10 }, null), { x: 10 });

// 4. ObjectSchema correctly merges object properties using MergeStrategy string identifiers overwrite, replace, and assign
const schemaWithStrings = new ObjectSchema({
  mode: {
    required: true,
    merge: "overwrite",
    validate: "string"
  },
  timeout: {
    required: false,
    merge: "replace",
    validate: "number"
  },
  headers: {
    required: false,
    merge: "assign",
    validate: "object"
  }
});

const baseConfig = {
  mode: "development",
  timeout: 5000,
  headers: { "Content-Type": "application/json", "X-Env": "dev" }
};

const overrideConfig1 = {
  mode: "production",
  headers: { "X-Env": "prod", "Authorization": "Bearer token" }
};

const merged1 = schemaWithStrings.merge(baseConfig, overrideConfig1);
assert.equal(merged1.mode, "production");
assert.equal(merged1.timeout, 5000);
assert.deepEqual(merged1.headers, {
  "Content-Type": "application/json",
  "X-Env": "prod",
  "Authorization": "Bearer token"
});

const overrideConfig2 = {
  mode: "staging",
  timeout: 10000,
  headers: { "X-Env": "stage" }
};
const merged2 = schemaWithStrings.merge(baseConfig, overrideConfig2);
assert.equal(merged2.mode, "staging");
assert.equal(merged2.timeout, 10000);

// 5. ObjectSchema accepts MergeStrategy static methods as direct function merge handlers for multi-object merges
const schemaWithMethods = new ObjectSchema({
  title: {
    required: true,
    merge: MergeStrategy.overwrite,
    validate: "string"
  },
  retries: {
    required: false,
    merge: MergeStrategy.replace,
    validate: "number"
  },
  settings: {
    required: false,
    merge: MergeStrategy.assign,
    validate: "object"
  }
});

const o1 = {
  title: "Draft",
  retries: 3,
  settings: { alpha: 1, beta: 2 }
};

const o2 = {
  title: "Review",
  settings: { beta: 20, gamma: 3 }
};

const o3 = {
  title: "Final",
  retries: 5,
  settings: { gamma: 30, delta: 4 }
};

const multiMerged = schemaWithMethods.merge(o1, o2, o3);
assert.equal(multiMerged.title, "Final");
assert.equal(multiMerged.retries, 5);
assert.deepEqual(multiMerged.settings, {
  alpha: 1,
  beta: 20,
  gamma: 30,
  delta: 4
});

console.log("MergeStrategy contract verified successfully.");