@babel/types 7.29.7: arrayExpression

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 @babel/types.arrayExpression in pkg:npm/%40babel/types@7.29.7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40babel/types@7.29.7
Demonstrate these symbols/APIs:
  - @babel/types.arrayExpression

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.

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      "name": "sample-babel-types-array-expression",
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    "node_modules/@babel/helper-string-parser": {
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      "resolved": "https://registry.npmjs.org/@babel/helper-string-parser/-/helper-string-parser-7.29.7.tgz",
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      "license": "MIT",
      "engines": {
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    "node_modules/@babel/helper-validator-identifier": {
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      "license": "MIT",
      "engines": {
        "node": ">=6.9.0"
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    "node_modules/@babel/types": {
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      "resolved": "https://registry.npmjs.org/@babel/types/-/types-7.29.7.tgz",
      "integrity": "sha512-4zBIxpPzowiZpusoFkyGVwakdRJUyuH5PxQ/PrqghfdFWWasvnCdPfQXHrenDai+gyLARulZjZowCOj6fjT4pA==",
      "license": "MIT",
      "dependencies": {
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      "engines": {
        "node": ">=6.9.0"
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{
  "name": "sample-babel-types-array-expression",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "@babel/types": "7.29.7"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @babel/types.arrayExpression in pkg:npm/%40babel/types@7.29.7",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40babel/types@7.29.7"
  ],
  "symbols": [
    "@babel/types.arrayExpression"
  ]
}

import * as t from "@babel/types";

/**
 * Creates an empty ArrayExpression AST node.
 * @returns {import('@babel/types').ArrayExpression}
 */
export function buildEmptyArray() {
  return t.arrayExpression();
}

/**
 * Creates an ArrayExpression AST node with given elements.
 * @param {Array<import('@babel/types').null | import('@babel/types').Expression | import('@babel/types').SpreadElement>} elements
 * @returns {import('@babel/types').ArrayExpression}
 */
export function buildArray(elements) {
  return t.arrayExpression(elements);
}

/**
 * Creates an ArrayExpression AST node with sparse holes.
 * @param {Array<import('@babel/types').null | import('@babel/types').Expression>} elementsWithHoles
 * @returns {import('@babel/types').ArrayExpression}
 */
export function buildSparseArray(elementsWithHoles) {
  return t.arrayExpression(elementsWithHoles);
}

/**
 * Creates an ArrayExpression AST node containing a SpreadElement.
 * @param {import('@babel/types').Expression} spreadTarget
 * @param {Array<import('@babel/types').Expression>} [leadingElements]
 * @returns {import('@babel/types').ArrayExpression}
 */
export function buildSpreadArray(spreadTarget, leadingElements = []) {
  return t.arrayExpression([...leadingElements, t.spreadElement(spreadTarget)]);
}

export { t };

import assert from "node:assert/strict";
import {
  arrayExpression,
  isArrayExpression,
  assertArrayExpression,
  numericLiteral,
  stringLiteral,
  booleanLiteral,
  identifier,
  spreadElement
} from "@babel/types";
import {
  buildEmptyArray,
  buildArray,
  buildSparseArray,
  buildSpreadArray
} from "../src/index.mjs";

// 1. creates an empty ArrayExpression AST node when elements argument is omitted
{
  const node = buildEmptyArray();
  assert.equal(node.type, "ArrayExpression");
  assert.deepEqual(node.elements, []);
  assert.equal(isArrayExpression(node), true);
  assert.doesNotThrow(() => assertArrayExpression(node));
}

// 2. creates an ArrayExpression AST node with ordered expression elements
{
  const elements = [numericLiteral(42), stringLiteral("hello"), booleanLiteral(false)];
  const node = buildArray(elements);
  assert.equal(node.type, "ArrayExpression");
  assert.equal(node.elements.length, 3);
  assert.equal(node.elements[0].type, "NumericLiteral");
  assert.equal(node.elements[0].value, 42);
  assert.equal(node.elements[1].type, "StringLiteral");
  assert.equal(node.elements[1].value, "hello");
  assert.equal(node.elements[2].type, "BooleanLiteral");
  assert.equal(node.elements[2].value, false);
}

// 3. supports null elements to represent sparse array holes
{
  const sparseElements = [numericLiteral(1), null, numericLiteral(3)];
  const node = buildSparseArray(sparseElements);
  assert.equal(node.type, "ArrayExpression");
  assert.equal(node.elements.length, 3);
  assert.equal(node.elements[0].value, 1);
  assert.equal(node.elements[1], null);
  assert.equal(node.elements[2].value, 3);
  assert.equal(isArrayExpression(node), true);
}

// 4. supports SpreadElement nodes as array expression elements
{
  const spreadTarget = identifier("items");
  const node = buildSpreadArray(spreadTarget, [stringLiteral("first")]);
  assert.equal(node.type, "ArrayExpression");
  assert.equal(node.elements.length, 2);
  assert.equal(node.elements[0].type, "StringLiteral");
  assert.equal(node.elements[1].type, "SpreadElement");
  assert.equal(node.elements[1].argument.type, "Identifier");
  assert.equal(node.elements[1].argument.name, "items");
}

// 5. validates ArrayExpression nodes using isArrayExpression and assertArrayExpression type guards
{
  const validNode = arrayExpression();
  const invalidNode = identifier("notAnArray");
  assert.equal(isArrayExpression(validNode), true);
  assert.equal(isArrayExpression(invalidNode), false);
  assert.equal(isArrayExpression(null), false);
  assert.equal(isArrayExpression({}), false);
  assert.doesNotThrow(() => assertArrayExpression(validNode));
  assert.throws(
    () => assertArrayExpression(invalidNode),
    /Expected type "ArrayExpression"/
  );
}

console.log("All @babel/types.arrayExpression contract assertions passed.");