node/test/parallel/test-fs-writefile-with-fd.js

'use strict';

// This test makes sure that `writeFile()` always writes from the current
// position of the file, instead of truncating the file, when used with file
// descriptors.

const common = require('../common');
const assert = require('assert');
const fs = require('fs');

const tmpdir = require('../common/tmpdir');
tmpdir.refresh();

{
  /* writeFileSync() test. */
  const filename = tmpdir.resolve('test.txt');

  /* Open the file descriptor. */
  const fd = fs.openSync(filename, 'w');
  try {
    /* Write only five characters, so that the position moves to five. */
    assert.strictEqual(fs.writeSync(fd, 'Hello'), 5);
    assert.strictEqual(fs.readFileSync(filename).toString(), 'Hello');

    /* Write some more with writeFileSync(). */
    fs.writeFileSync(fd, 'World');

    /* New content should be written at position five, instead of zero. */
    assert.strictEqual(fs.readFileSync(filename).toString(), 'HelloWorld');
  } finally {
    fs.closeSync(fd);
  }
}

const fdsToCloseOnExit = [];
process.on('beforeExit', common.mustCall(() => {
  for (const fd of fdsToCloseOnExit) {
    try {
      fs.closeSync(fd);
    } catch {
      // Failed to close, ignore
    }
  }
}));

{
  /* writeFile() test. */
  const file = tmpdir.resolve('test1.txt');

  /* Open the file descriptor. */
  fs.open(file, 'w', common.mustSucceed((fd) => {
    fdsToCloseOnExit.push(fd);
    /* Write only five characters, so that the position moves to five. */
    fs.write(fd, 'Hello', common.mustSucceed((bytes) => {
      assert.strictEqual(bytes, 5);
      assert.strictEqual(fs.readFileSync(file).toString(), 'Hello');

      /* Write some more with writeFile(). */
      fs.writeFile(fd, 'World', common.mustSucceed(() => {
        /* New content should be written at position five, instead of zero. */
        assert.strictEqual(fs.readFileSync(file).toString(), 'HelloWorld');
      }));
    }));
  }));
}


// Test read-only file descriptor
{
  const file = tmpdir.resolve('test.txt');

  fs.open(file, 'r', common.mustSucceed((fd) => {
    fdsToCloseOnExit.push(fd);
    fs.writeFile(fd, 'World', common.expectsError(/EBADF/));
  }));
}

// Test with an AbortSignal
{
  const controller = new AbortController();
  const signal = controller.signal;
  const file = tmpdir.resolve('test.txt');

  fs.open(file, 'w', common.mustSucceed((fd) => {
    fdsToCloseOnExit.push(fd);
    fs.writeFile(fd, 'World', { signal }, common.expectsError({
      name: 'AbortError'
    }));
  }));

  controller.abort();
}