CodeSampleX

Sample

@babel/plugin-transform-arrow-functions 8.0.1: transform

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

sha256:d2f275d4ffc040b9917cdfb2425adfe3a043339795cf227c88b9f198861aab67

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 linux 24 · ubuntu · glibc 2.39 x64 npm

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…		 2026-08-26

Case

HOW
Goal
verify transform in pkg:npm/%40babel/plugin-transform-arrow-functions@8.0.1
Packages
Symbols
  • transform
Created
2026-08-26T05:11:04Z

Contract

  1. Plugin default export is a function factory asserting Babel version range ^7.0.0-0 || ^8.0.0
  2. Plugin factory returns plugin descriptor named transform-arrow-functions with an ArrowFunctionExpression visitor method
  3. ArrowFunctionExpression visitor transforms arrow functions with allowInsertArrow false and default noNewArrows true
  4. ArrowFunctionExpression visitor sets noNewArrows to false when spec option is true
  5. ArrowFunctionExpression visitor prioritizes noNewArrows compiler assumption over spec option
  6. ArrowFunctionExpression visitor skips transformation when AST node is not an arrow function expression
  7. Module helper applyArrowTransform executes plugin visitor and returns resulting transformation configuration

Files

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

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 transform in pkg:npm/%40babel/plugin-transform-arrow-functions@8.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40babel/plugin-transform-arrow-functions@8.0.1
Demonstrate these symbols/APIs:
  - transform

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
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package-lock.json
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package.json
{
  "name": "sample-babel-plugin-transform-arrow-functions",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "@babel/plugin-transform-arrow-functions": "8.0.1"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify transform in pkg:npm/%40babel/plugin-transform-arrow-functions@8.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40babel/plugin-transform-arrow-functions@8.0.1"
  ],
  "symbols": [
    "transform"
  ]
}
src/index.mjs
import arrowFunctionsPluginModule from "@babel/plugin-transform-arrow-functions";

export const arrowFunctionsPlugin =
  typeof arrowFunctionsPluginModule === "function"
    ? arrowFunctionsPluginModule
    : arrowFunctionsPluginModule.default || arrowFunctionsPluginModule;

/**
 * Creates an instance of the transform-arrow-functions plugin with given API and options.
 */
export function createArrowPluginInstance(api = {}, options = {}) {
  const normalizedApi = {
    assertVersion: (range) => {
      if (typeof api.assertVersion === "function") {
        api.assertVersion(range);
      }
    },
    assumption: (name) => {
      if (typeof api.assumption === "function") {
        return api.assumption(name);
      }
      return undefined;
    },
    ...api
  };
  return arrowFunctionsPlugin(normalizedApi, options);
}

/**
 * Invokes the ArrowFunctionExpression visitor method on a given AST path.
 */
export function transformArrowFunction(pluginInstance, path) {
  if (!pluginInstance?.visitor?.ArrowFunctionExpression) {
    throw new Error("Invalid plugin instance: missing ArrowFunctionExpression visitor");
  }
  return pluginInstance.visitor.ArrowFunctionExpression(path);
}

/**
 * Simulates arrow function transformation on an AST path object.
 */
export function applyArrowTransform(options = {}, assumptions = {}, customPath = null) {
  let transformedConfig = null;
  const path = customPath || {
    _isArrow: true,
    isArrowFunctionExpression() {
      return this._isArrow;
    },
    arrowFunctionToExpression(opts) {
      transformedConfig = opts;
    }
  };

  const api = {
    assertVersion: () => {},
    assumption: (name) => assumptions[name]
  };

  const pluginInstance = createArrowPluginInstance(api, options);
  transformArrowFunction(pluginInstance, path);
  return { pluginInstance, path, transformedConfig };
}
test/contract.mjs
import assert from "node:assert/strict";
import arrowFunctionsPluginModule from "@babel/plugin-transform-arrow-functions";
import {
  arrowFunctionsPlugin,
  createArrowPluginInstance,
  transformArrowFunction,
  applyArrowTransform
} from "../src/index.mjs";

const rawPlugin =
  typeof arrowFunctionsPluginModule === "function"
    ? arrowFunctionsPluginModule
    : arrowFunctionsPluginModule.default || arrowFunctionsPluginModule;

// Contract 1: Plugin default export is a function factory asserting Babel version range ^7.0.0-0 || ^8.0.0
{
  assert.equal(typeof arrowFunctionsPlugin, "function");
  assert.equal(typeof rawPlugin, "function");

  let assertedVersion = null;
  const api = {
    assertVersion: (v) => {
      assertedVersion = v;
    },
    assumption: () => undefined
  };
  const pluginInstance = rawPlugin(api, {});
  assert.equal(assertedVersion, "^7.0.0-0 || ^8.0.0");
  assert.ok(pluginInstance);
}

// Contract 2: Plugin factory returns plugin descriptor named transform-arrow-functions with an ArrowFunctionExpression visitor method
{
  const api = {
    assertVersion: () => {},
    assumption: () => undefined
  };
  const pluginInstance = createArrowPluginInstance(api, {});
  assert.equal(pluginInstance.name, "transform-arrow-functions");
  assert.ok(pluginInstance.visitor);
  assert.equal(typeof pluginInstance.visitor.ArrowFunctionExpression, "function");
}

// Contract 3: ArrowFunctionExpression visitor transforms arrow functions with allowInsertArrow false and default noNewArrows true
{
  const api = {
    assertVersion: () => {},
    assumption: () => undefined
  };
  const pluginInstance = createArrowPluginInstance(api, {});
  let receivedOptions = null;
  const mockPath = {
    isArrowFunctionExpression: () => true,
    arrowFunctionToExpression: (opts) => {
      receivedOptions = opts;
    }
  };

  transformArrowFunction(pluginInstance, mockPath);
  assert.deepEqual(receivedOptions, {
    allowInsertArrow: false,
    noNewArrows: true
  });
}

// Contract 4: ArrowFunctionExpression visitor sets noNewArrows to false when spec option is true
{
  const api = {
    assertVersion: () => {},
    assumption: () => undefined
  };
  const pluginInstance = createArrowPluginInstance(api, { spec: true });
  let receivedOptions = null;
  const mockPath = {
    isArrowFunctionExpression: () => true,
    arrowFunctionToExpression: (opts) => {
      receivedOptions = opts;
    }
  };

  transformArrowFunction(pluginInstance, mockPath);
  assert.deepEqual(receivedOptions, {
    allowInsertArrow: false,
    noNewArrows: false
  });
}

// Contract 5: ArrowFunctionExpression visitor prioritizes noNewArrows compiler assumption over spec option
{
  // When assumption noNewArrows is true, it overrides spec: true
  {
    const apiWithAssumptionTrue = {
      assertVersion: () => {},
      assumption: (name) => (name === "noNewArrows" ? true : undefined)
    };
    const pluginInstance = createArrowPluginInstance(apiWithAssumptionTrue, { spec: true });
    let receivedOptions = null;
    const mockPath = {
      isArrowFunctionExpression: () => true,
      arrowFunctionToExpression: (opts) => {
        receivedOptions = opts;
      }
    };
    transformArrowFunction(pluginInstance, mockPath);
    assert.deepEqual(receivedOptions, {
      allowInsertArrow: false,
      noNewArrows: true
    });
  }

  // When assumption noNewArrows is false, it overrides spec: false
  {
    const apiWithAssumptionFalse = {
      assertVersion: () => {},
      assumption: (name) => (name === "noNewArrows" ? false : undefined)
    };
    const pluginInstance = createArrowPluginInstance(apiWithAssumptionFalse, { spec: false });
    let receivedOptions = null;
    const mockPath = {
      isArrowFunctionExpression: () => true,
      arrowFunctionToExpression: (opts) => {
        receivedOptions = opts;
      }
    };
    transformArrowFunction(pluginInstance, mockPath);
    assert.deepEqual(receivedOptions, {
      allowInsertArrow: false,
      noNewArrows: false
    });
  }
}

// Contract 6: ArrowFunctionExpression visitor skips transformation when AST node is not an arrow function expression
{
  const api = {
    assertVersion: () => {},
    assumption: () => undefined
  };
  const pluginInstance = createArrowPluginInstance(api, {});
  let called = false;
  const nonArrowPath = {
    isArrowFunctionExpression: () => false,
    arrowFunctionToExpression: () => {
      called = true;
    }
  };

  transformArrowFunction(pluginInstance, nonArrowPath);
  assert.equal(called, false);
}

// Contract 7: Module helper applyArrowTransform executes plugin visitor and returns resulting transformation configuration
{
  const { transformedConfig: defaultResult } = applyArrowTransform();
  assert.deepEqual(defaultResult, {
    allowInsertArrow: false,
    noNewArrows: true
  });

  const { transformedConfig: specResult } = applyArrowTransform({ spec: true });
  assert.deepEqual(specResult, {
    allowInsertArrow: false,
    noNewArrows: false
  });

  const { transformedConfig: assumptionResult } = applyArrowTransform(
    { spec: false },
    { noNewArrows: false }
  );
  assert.deepEqual(assumptionResult, {
    allowInsertArrow: false,
    noNewArrows: false
  });
}

console.log("All @babel/plugin-transform-arrow-functions contract tests passed successfully.");

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