CodeSampleX

Sample

@babel/plugin-transform-block-scoping 8.0.1

Verified sample for npm @babel/plugin-transform-block-scoping 8.0.1. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:bdca2619c137e7f9964a959780b1cf86f366e9d26dc7994d0534b6bd4e64b7e5

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment node 22.23 linux 24 · ubuntu · glibc 2.39 x64 node 22.23 javascript npm 10

Verification-run environments

Environment Contract Stages Run
node 22 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22-alpine@sha256:c610fcdfb1d5…		 2026-08-27

Case

HOW
Goal
verify pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1
Packages
Environment
node 22.23.2
Created
2026-08-27T20:43:57Z

Contract

  1. transformBlockScoping transforms let and const variable declarations into var
  2. transformBlockScoping renames colliding variable identifiers across nested block scopes
  3. transformBlockScoping wraps loop body in a closure function when loop variable is captured
  4. transformBlockScoping throwIfClosureRequired option throws error when loop closure is needed
  5. transformBlockScoping tdz option inserts runtime temporal dead zone validation
  6. transformBlockScoping preserves variable scoping and closure execution semantics in runtime

Files

  • PROMPT.md
  • csx.json
  • index.js
  • package-lock.json
  • package.json
  • spec.json
  • test/contract.js

Download the source artifact (tar.gz)

Source

PROMPT.md
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 pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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.
csx.json
{"case":{"caseId":"case:sha256:a3eb64e7abfe03a9861ecf75103c0e41e6b5cfc11c620180440491175415c428","constraints":{"executionContext":"node"},"contract":["transformBlockScoping transforms let and const variable declarations into var","transformBlockScoping renames colliding variable identifiers across nested block scopes","transformBlockScoping wraps loop body in a closure function when loop variable is captured","transformBlockScoping throwIfClosureRequired option throws error when loop closure is needed","transformBlockScoping tdz option inserts runtime temporal dead zone validation","transformBlockScoping preserves variable scoping and closure execution semantics in runtime"],"goal":"verify pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1","kind":"HOW","packages":["pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1"],"schemaVersion":1},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1"],"schemaVersion":1,"subject":"pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1","verifierAdapter":"node-typescript@1"}
index.js
const babel = require('@babel/core');
const blockScopingPlugin = require('@babel/plugin-transform-block-scoping');

/**
 * Transform block-scoped declarations (let, const) to var using @babel/plugin-transform-block-scoping.
 *
 * @param {string} code - The input JavaScript code containing block scopes or let/const declarations.
 * @param {object} [pluginOptions] - Optional configuration options for the plugin (e.g. throwIfClosureRequired, tdz).
 * @param {object} [babelOptions] - Optional Babel compiler options.
 * @returns {string} The transformed JavaScript code.
 */
function transformBlockScoping(code, pluginOptions = {}, babelOptions = {}) {
  const plugin = blockScopingPlugin.default || blockScopingPlugin;
  const plugins = Object.keys(pluginOptions).length > 0
    ? [[plugin, pluginOptions]]
    : [plugin];

  const result = babel.transformSync(code, {
    plugins,
    configFile: false,
    babelrc: false,
    comments: false,
    ...babelOptions
  });

  return result ? result.code : '';
}

module.exports = {
  transformBlockScoping,
  blockScopingPlugin: blockScopingPlugin.default || blockScopingPlugin
};
package-lock.json
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package.json
{
  "name": "sample-babel-plugin-transform-block-scoping",
  "version": "1.0.0",
  "private": true,
  "type": "commonjs",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "license": "MIT-0",
  "dependencies": {
    "@babel/core": "8.0.1",
    "@babel/plugin-transform-block-scoping": "8.0.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40babel/plugin-transform-block-scoping@8.0.1"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}
test/contract.js
const assert = require('assert');
const { transformBlockScoping, blockScopingPlugin } = require('../index');

function runContractTests() {
  // 1. Verify plugin export
  assert.strictEqual(typeof blockScopingPlugin, 'function', 'blockScopingPlugin should be a function');

  // 2. Transform let and const variable declarations into var
  const basicCode = 'let count = 10; const maxLimit = 100;';
  const transformedBasic = transformBlockScoping(basicCode);
  assert.ok(transformedBasic.includes('var count = 10;'), 'let declarations should be transformed to var');
  assert.ok(transformedBasic.includes('var maxLimit = 100;'), 'const declarations should be transformed to var');
  assert.ok(!transformedBasic.includes('let '), 'Transformed code should not contain let keyword');
  assert.ok(!transformedBasic.includes('const '), 'Transformed code should not contain const keyword');

  // 3. Rename colliding variable identifiers across nested block scopes
  const nestedScopeCode = [
    'function compute() {',
    '  let val = 1;',
    '  {',
    '    let val = 2;',
    '    val += 10;',
    '  }',
    '  return val;',
    '}'
  ].join('\n');
  const transformedNested = transformBlockScoping(nestedScopeCode);
  assert.ok(transformedNested.includes('var val = 1;'), 'Outer variable should be declared with var');
  assert.ok(transformedNested.includes('var _val = 2;'), 'Inner variable should be renamed to prevent collision');
  assert.ok(transformedNested.includes('_val += 10;'), 'Inner variable updates should use renamed identifier');

  // 4. Wrap loop body in a closure function when loop variable is captured
  const loopClosureCode = [
    'const handlers = [];',
    'for (let i = 0; i < 3; i++) {',
    '  handlers.push(() => i * 2);',
    '}'
  ].join('\n');
  const transformedLoop = transformBlockScoping(loopClosureCode);
  assert.ok(transformedLoop.includes('var _loop = function'), 'Loop body capturing let binding should be wrapped in helper function');
  assert.ok(transformedLoop.includes('_loop(i);'), 'Loop iteration should invoke helper function with loop variable');

  // 5. throwIfClosureRequired option throws error when loop closure is needed
  let threwExpectedError = false;
  try {
    transformBlockScoping(loopClosureCode, { throwIfClosureRequired: true });
  } catch (err) {
    threwExpectedError = true;
    assert.ok(err.message.includes('throwIfClosureRequired'), 'Error message should indicate throwIfClosureRequired constraint');
  }
  assert.strictEqual(threwExpectedError, true, 'transformBlockScoping should throw when throwIfClosureRequired is true and loop closure is needed');

  // 6. tdz option inserts runtime temporal dead zone validation
  const tdzCode = 'console.log(myVar); let myVar = "ready";';
  const transformedTdz = transformBlockScoping(tdzCode, { tdz: true });
  assert.ok(transformedTdz.includes('function _tdz') || transformedTdz.includes('_tdz'), 'TDZ transform should include TDZ helper check');

  // 7. Preserve variable scoping and closure execution semantics in runtime
  const runnableNestedCode = `
    ${transformedNested}
    return compute();
  `;
  const computeFn = new Function(runnableNestedCode);
  assert.strictEqual(computeFn(), 1, 'Transformed nested scope code should execute and return outer variable value');

  const runnableLoopCode = `
    ${transformedLoop}
    return handlers.map(fn => fn());
  `;
  const loopFn = new Function(runnableLoopCode);
  assert.deepStrictEqual(loopFn(), [0, 2, 4], 'Transformed loop closure code should capture distinct loop iteration values');

  console.log('All contract assertions passed successfully.');
}

runContractTests();

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