CodeSampleX

Sample

esbuild 0.28.2

Verified sample for npm esbuild 0.28.2. The contract ran on node 22 · linux alpine/x64 · docker and passed: esbuild.buildSync bundles TypeScript source code…

sha256:78f055af46705ede093551fd58c78c2b1beb87bfe05918fe1f3515fbebbc039c

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
2
Signing keys that built it
2
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 ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-19
node 22 · linux debian/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22@sha256:8a34c4ab3ea2…		 2026-09-08

Case

HOW
Goal
verify pkg:npm/esbuild@0.28.2
Packages
Environment
node 22.23.2
Created
2026-08-19T18:00:28Z

Contract

  1. esbuild.buildSync bundles TypeScript source code into CommonJS JavaScript in memory
  2. esbuild.transformSync transpiles TypeScript code and JSX syntax to plain JavaScript with minification
  3. esbuild.formatMessagesSync formats diagnostic error messages with file location and source line context
  4. esbuild.analyzeMetafileSync computes formatted bundle breakdown from build metafile

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.js
  • 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/esbuild@0.28.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/esbuild@0.28.2
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:sha256:6425c849cf565040a06adeda569b3e6c2289ee1b4d4cf453b188b505bb66d3c5","constraints":{"executionContext":"node"},"contract":["esbuild.buildSync bundles TypeScript source code into CommonJS JavaScript in memory","esbuild.transformSync transpiles TypeScript code and JSX syntax to plain JavaScript with minification","esbuild.formatMessagesSync formats diagnostic error messages with file location and source line context","esbuild.analyzeMetafileSync computes formatted bundle breakdown from build metafile"],"goal":"verify pkg:npm/esbuild@0.28.2","kind":"HOW","packages":["pkg:npm/esbuild@0.28.2"],"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/esbuild@0.28.2"],"schemaVersion":1,"verifierAdapter":"node-typescript@1"}
package-lock.json
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  }
}
package.json
{
  "name": "esbuild-sample",
  "version": "1.0.0",
  "dependencies": {
    "esbuild": "0.28.2"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/esbuild@0.28.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/esbuild@0.28.2"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}
src/index.js
const esbuild = require('esbuild');

/**
 * Synchronously bundles source code passed via in-memory stdin.
 *
 * @param {string} contents Source code string to bundle
 * @param {object} [options={}] Additional esbuild build options
 * @returns {import('esbuild').BuildResult}
 */
function bundleInMemory(contents, options = {}) {
  return esbuild.buildSync({
    stdin: {
      contents,
      loader: options.loader || 'ts',
      resolveDir: options.resolveDir || process.cwd(),
    },
    bundle: options.bundle !== undefined ? options.bundle : true,
    format: options.format || 'cjs',
    write: false,
    minify: options.minify || false,
    target: options.target,
    sourcemap: options.sourcemap,
    metafile: options.metafile,
  });
}

/**
 * Synchronously transpiles a code snippet (TypeScript/JSX/TSX).
 *
 * @param {string} code Source code string to transpile
 * @param {import('esbuild').TransformOptions} [options={}]
 * @returns {import('esbuild').TransformResult}
 */
function transformCode(code, options = {}) {
  return esbuild.transformSync(code, {
    loader: options.loader || 'ts',
    jsx: options.jsx || 'transform',
    jsxFactory: options.jsxFactory || 'React.createElement',
    jsxFragment: options.jsxFragment || 'React.Fragment',
    minify: options.minify || false,
    target: options.target,
  });
}

/**
 * Synchronously formats diagnostic error or warning messages.
 *
 * @param {import('esbuild').PartialMessage[]} messages Array of diagnostic messages
 * @param {import('esbuild').FormatMessagesOptions} [options={}]
 * @returns {string[]}
 */
function formatDiagnostics(messages, options = {}) {
  return esbuild.formatMessagesSync(messages, {
    kind: options.kind || 'error',
    color: options.color !== undefined ? options.color : false,
    terminalWidth: options.terminalWidth,
  });
}

/**
 * Synchronously analyzes a build metafile and produces a formatted string report.
 *
 * @param {import('esbuild').Metafile} metafile Build metafile
 * @param {import('esbuild').AnalyzeMetafileOptions} [options={}]
 * @returns {string}
 */
function analyzeBundle(metafile, options = {}) {
  return esbuild.analyzeMetafileSync(metafile, {
    verbose: options.verbose || false,
    color: options.color !== undefined ? options.color : false,
  });
}

module.exports = {
  bundleInMemory,
  transformCode,
  formatDiagnostics,
  analyzeBundle,
};
test/contract.js
const assert = require('node:assert/strict');
const esbuild = require('esbuild');
const {
  bundleInMemory,
  transformCode,
  formatDiagnostics,
  analyzeBundle,
} = require('../src/index.js');

// Contract 1: esbuild.buildSync bundles TypeScript source code into CommonJS JavaScript in memory
{
  const tsSource = `
    interface Calculator {
      calculate(x: number, y: number): number;
    }
    class Adder implements Calculator {
      calculate(x: number, y: number): number {
        return x + y;
      }
    }
    export const sum = (a: number, b: number): number => new Adder().calculate(a, b);
  `;

  const result = bundleInMemory(tsSource, { loader: 'ts', format: 'cjs', metafile: true });

  assert.ok(result.outputFiles && result.outputFiles.length === 1, 'buildSync should produce 1 output file in memory');
  const bundleText = result.outputFiles[0].text;

  // Verify TypeScript type annotations and interfaces were stripped
  assert.strictEqual(bundleText.includes('interface Calculator'), false, 'Interface declarations should be stripped');
  assert.strictEqual(bundleText.includes('x: number'), false, 'Type annotations should be stripped');

  // Verify exported symbol is properly exported in CommonJS format
  assert.ok(bundleText.includes('sum'), 'CommonJS export for sum should be generated');
  assert.ok(bundleText.includes('module.exports'), 'CommonJS module.exports should be present');
}

// Contract 2: esbuild.transformSync transpiles TypeScript code and JSX syntax to plain JavaScript with minification
{
  const tsxSource = `
    interface CardProps {
      title: string;
      active: boolean;
    }
    export const Card = ({ title, active }: CardProps) => (
      <div className={active ? 'active' : 'inactive'}>
        <h1>{title}</h1>
      </div>
    );
  `;

  const transformResult = transformCode(tsxSource, {
    loader: 'tsx',
    jsx: 'transform',
    jsxFactory: 'React.createElement',
    jsxFragment: 'React.Fragment',
  });

  const transformedText = transformResult.code;

  // Verify TypeScript types are stripped
  assert.strictEqual(transformedText.includes('interface CardProps'), false, 'Interface should be stripped');
  assert.strictEqual(transformedText.includes(': CardProps'), false, 'Type annotation should be stripped');

  // Verify JSX tags were converted to React.createElement calls
  assert.ok(transformedText.includes('React.createElement("div"'), 'JSX div tag should be converted to React.createElement');
  assert.ok(transformedText.includes('React.createElement("h1"'), 'JSX h1 tag should be converted to React.createElement');

  // Verify minification option works as expected
  const minifiedResult = transformCode('const score: number = 10 + 20 + 30;', {
    loader: 'ts',
    minify: true,
  });
  assert.strictEqual(minifiedResult.code.trim(), 'const score=60;', 'Constant folding and minification should occur');
}

// Contract 3: esbuild.formatMessagesSync formats diagnostic error messages with file location and source line context
{
  const mockDiagnostic = {
    text: 'Type mismatch error',
    location: {
      file: 'src/calculator.ts',
      line: 15,
      column: 4,
      length: 8,
      lineText: 'const res: string = 12345;',
    },
  };

  const formattedMessages = formatDiagnostics([mockDiagnostic], {
    kind: 'error',
    color: false,
  });

  assert.strictEqual(formattedMessages.length, 1, 'Should return exactly 1 formatted message');
  const formattedText = formattedMessages[0];

  assert.ok(formattedText.includes('src/calculator.ts:15:4'), 'Formatted output should contain file name, line, and column');
  assert.ok(formattedText.includes('Type mismatch error'), 'Formatted output should contain the error text');
  assert.ok(formattedText.includes('const res: string = 12345;'), 'Formatted output should contain the context line text');
}

// Contract 4: esbuild.analyzeMetafileSync computes formatted bundle breakdown from build metafile
{
  const buildResult = bundleInMemory('export const val = 100;', { loader: 'ts', metafile: true });
  assert.ok(buildResult.metafile, 'Metafile should be generated');

  const analysisReport = analyzeBundle(buildResult.metafile, { verbose: false });
  assert.strictEqual(typeof analysisReport, 'string', 'Analysis report should be a string');
  assert.ok(analysisReport.includes('stdin.js') || analysisReport.includes('<stdin>'), 'Analysis report should reference stdin input');
}

console.log('All pkg:npm/esbuild@0.28.2 contracts passed successfully.');

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