bare-stream 2.13.3: Transform

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 bare-stream.Transform in pkg:npm/bare-stream@2.13.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/bare-stream@2.13.3
Demonstrate these symbols/APIs:
  - bare-stream.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.

{"case":{"caseId":"case:sha256:c12e9e37506f821531f1e589b0168c327f0348c61822a6a4fd43f61df4424041","contract":["Transform processes input chunks and pushes converted data downstream","Transform flush hook emits remaining data before stream finish and end","Transform subclasses can override _transform and _flush methods","Transform defaults to passthrough behavior when no transform function is provided","Transform propagates errors passed to callback and emits error event","Transform supports async iteration over transformed output chunks","Transform integrates with pipeline to process data from Readable to Writable"],"goal":"verify bare-stream.Transform in pkg:npm/bare-stream@2.13.3","kind":"HOW","packages":["pkg:npm/bare-stream@2.13.3"],"schemaVersion":1,"symbols":["bare-stream.Transform"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/bare-stream@2.13.3"],"schemaVersion":1,"subject":"pkg:npm/bare-stream@2.13.3","symbols":["bare-stream.Transform"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-bare-stream-transform",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-bare-stream-transform",
      "version": "1.0.0",
      "dependencies": {
        "bare-stream": "2.13.3"
      }
    },
    "node_modules/b4a": {
      "version": "1.8.1",
      "resolved": "https://registry.npmjs.org/b4a/-/b4a-1.8.1.tgz",
      "integrity": "sha512-aiqre1Nr0B/6DgE2N5vwTc+2/oQZ4Wh1t4NznYY4E00y8LCt6NqdRv81so00oo27D8MVKTpUa/MwUUtBLXCoDw==",
      "license": "Apache-2.0",
      "peerDependencies": {
        "react-native-b4a": "*"
      },
      "peerDependenciesMeta": {
        "react-native-b4a": {
          "optional": true
        }
      }
    },
    "node_modules/bare-events": {
      "version": "2.9.2",
      "resolved": "https://registry.npmjs.org/bare-events/-/bare-events-2.9.2.tgz",
      "integrity": "sha512-AIPKioV7/Y/8KfZ3AAhjPJxLLbY49S64Ym5DakZlUg75qQiTgUq9hEJoEwa4eUezPUlXRy/i5NpsKvo9jgKmoA==",
      "license": "Apache-2.0",
      "peerDependencies": {
        "bare-abort-controller": "*"
      },
      "peerDependenciesMeta": {
        "bare-abort-controller": {
          "optional": true
        }
      }
    },
    "node_modules/bare-stream": {
      "version": "2.13.3",
      "resolved": "https://registry.npmjs.org/bare-stream/-/bare-stream-2.13.3.tgz",
      "integrity": "sha512-Kc+brLqvEqGkjyfiwJmImAOqLZL7OsoLKuavx+hJjgVV3nLTOjloJyPMFxjUPerGGHrNH0fLU06jjykMLWrERQ==",
      "license": "Apache-2.0",
      "dependencies": {
        "b4a": "^1.8.1",
        "streamx": "^2.25.0",
        "teex": "^1.0.1"
      },
      "peerDependencies": {
        "bare-abort-controller": "*",
        "bare-buffer": "*",
        "bare-events": "*"
      },
      "peerDependenciesMeta": {
        "bare-abort-controller": {
          "optional": true
        },
        "bare-buffer": {
          "optional": true
        },
        "bare-events": {
          "optional": true
        }
      }
    },
    "node_modules/events-universal": {
      "version": "1.0.1",
      "resolved": "https://registry.npmjs.org/events-universal/-/events-universal-1.0.1.tgz",
      "integrity": "sha512-LUd5euvbMLpwOF8m6ivPCbhQeSiYVNb8Vs0fQ8QjXo0JTkEHpz8pxdQf0gStltaPpw0Cca8b39KxvK9cfKRiAw==",
      "license": "Apache-2.0",
      "dependencies": {
        "bare-events": "^2.7.0"
      }
    },
    "node_modules/fast-fifo": {
      "version": "1.3.2",
      "resolved": "https://registry.npmjs.org/fast-fifo/-/fast-fifo-1.3.2.tgz",
      "integrity": "sha512-/d9sfos4yxzpwkDkuN7k2SqFKtYNmCTzgfEpz82x34IM9/zc8KGxQoXg1liNC/izpRM/MBdt44Nmx41ZWqk+FQ==",
      "license": "MIT"
    },
    "node_modules/streamx": {
      "version": "2.28.1",
      "resolved": "https://registry.npmjs.org/streamx/-/streamx-2.28.1.tgz",
      "integrity": "sha512-zEzXb0s5Cds7tqMH6rhZ05lcJydCWiQPEwiNngVqzsxCc962vLY4Uw+mW7od8kDH258k2Uz/JrOkdIAAhSh9VA==",
      "license": "MIT",
      "dependencies": {
        "events-universal": "^1.0.0",
        "fast-fifo": "^1.3.2",
        "text-decoder": "^1.1.0"
      }
    },
    "node_modules/teex": {
      "version": "1.0.1",
      "resolved": "https://registry.npmjs.org/teex/-/teex-1.0.1.tgz",
      "integrity": "sha512-eYE6iEI62Ni1H8oIa7KlDU6uQBtqr4Eajni3wX7rpfXD8ysFx8z0+dri+KWEPWpBsxXfxu58x/0jvTVT1ekOSg==",
      "license": "MIT",
      "dependencies": {
        "streamx": "^2.12.5"
      }
    },
    "node_modules/text-decoder": {
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      "resolved": "https://registry.npmjs.org/text-decoder/-/text-decoder-1.2.7.tgz",
      "integrity": "sha512-vlLytXkeP4xvEq2otHeJfSQIRyWxo/oZGEbXrtEEF9Hnmrdly59sUbzZ/QgyWuLYHctCHxFF4tRQZNQ9k60ExQ==",
      "license": "Apache-2.0",
      "dependencies": {
        "b4a": "^1.6.4"
      }
    }
  }
}

{
  "name": "sample-bare-stream-transform",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "bare-stream": "2.13.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify bare-stream.Transform in pkg:npm/bare-stream@2.13.3",
  "kind": "HOW",
  "packages": [
    "pkg:npm/bare-stream@2.13.3"
  ],
  "symbols": [
    "bare-stream.Transform"
  ]
}

import assert from 'node:assert/strict';
import { Transform, Readable, Writable, pipeline, isStream, isReadable, isWritable } from 'bare-stream';

// 1. Transform processes input chunks and pushes converted data downstream
await new Promise((resolve, reject) => {
  const transformed = [];
  const tr = new Transform({
    transform(chunk, encoding, cb) {
      this.push(chunk.toString().toUpperCase());
      cb(null);
    }
  });

  assert.equal(isStream(tr), true);
  assert.equal(isReadable(tr), true);
  assert.equal(isWritable(tr), true);

  tr.on('data', (chunk) => {
    transformed.push(chunk.toString());
  });

  tr.on('end', () => {
    try {
      assert.deepEqual(transformed, ['FOO', 'BAR']);
      resolve();
    } catch (err) {
      reject(err);
    }
  });

  tr.on('error', reject);

  tr.write('foo');
  tr.end('bar');
});

// 2. Transform flush hook emits remaining data before stream finish and end
await new Promise((resolve, reject) => {
  const chunks = [];
  const tr = new Transform({
    transform(chunk, encoding, cb) {
      this.push(chunk.toString());
      cb(null);
    },
    flush(cb) {
      this.push('tail');
      cb(null);
    }
  });

  tr.on('data', (chunk) => {
    chunks.push(chunk.toString());
  });

  tr.on('end', () => {
    try {
      assert.deepEqual(chunks, ['head', 'tail']);
      resolve();
    } catch (err) {
      reject(err);
    }
  });

  tr.on('error', reject);

  tr.write('head');
  tr.end();
});

// 3. Transform subclasses can override _transform and _flush methods
await new Promise((resolve, reject) => {
  class CustomTransform extends Transform {
    _transform(chunk, encoding, cb) {
      this.push(chunk.toString() + '!');
      cb(null);
    }
    _flush(cb) {
      this.push('DONE');
      cb(null);
    }
  }

  const tr = new CustomTransform();
  const chunks = [];

  tr.on('data', (chunk) => {
    chunks.push(chunk.toString());
  });

  tr.on('end', () => {
    try {
      assert.deepEqual(chunks, ['hello!', 'DONE']);
      resolve();
    } catch (err) {
      reject(err);
    }
  });

  tr.on('error', reject);

  tr.write('hello');
  tr.end();
});

// 4. Transform defaults to passthrough behavior when no transform function is provided
await new Promise((resolve, reject) => {
  const tr = new Transform();
  const chunks = [];

  tr.on('data', (chunk) => {
    chunks.push(chunk.toString());
  });

  tr.on('end', () => {
    try {
      assert.deepEqual(chunks, ['passthrough-data']);
      resolve();
    } catch (err) {
      reject(err);
    }
  });

  tr.on('error', reject);

  tr.write('passthrough-data');
  tr.end();
});

// 5. Transform propagates errors passed to callback and emits error event
await new Promise((resolve, reject) => {
  const tr = new Transform({
    transform(chunk, encoding, cb) {
      cb(new Error('transform boom'));
    }
  });

  let errorCaught = false;
  tr.on('error', (err) => {
    if (err.message === 'transform boom') {
      errorCaught = true;
    }
  });

  tr.on('close', () => {
    try {
      assert.equal(errorCaught, true);
      resolve();
    } catch (err) {
      reject(err);
    }
  });

  tr.write('trigger error');
});

// 6. Transform supports async iteration over transformed output chunks
{
  const tr = new Transform({
    transform(chunk, encoding, cb) {
      this.push(chunk.toString().toUpperCase());
      cb(null);
    }
  });

  tr.write('one');
  tr.write('two');
  tr.end();

  const collected = [];
  for await (const chunk of tr) {
    collected.push(chunk.toString());
  }

  assert.deepEqual(collected, ['ONE', 'TWO']);
}

// 7. Transform integrates with pipeline to process data from Readable to Writable
await new Promise((resolve, reject) => {
  let index = 0;
  const items = ['alpha', 'beta'];
  const src = new Readable({
    read() {
      if (index < items.length) {
        this.push(items[index++]);
      } else {
        this.push(null);
      }
    }
  });

  const tr = new Transform({
    transform(chunk, encoding, cb) {
      this.push(`[${chunk.toString()}]`);
      cb(null);
    }
  });

  const destResult = [];
  const dest = new Writable({
    write(chunk, encoding, cb) {
      destResult.push(chunk.toString());
      cb(null);
    }
  });

  pipeline(src, tr, dest, (err) => {
    if (err) return reject(err);
    try {
      assert.deepEqual(destResult, ['[alpha]', '[beta]']);
      resolve();
    } catch (err) {
      reject(err);
    }
  });
});