Function compareAndWriteFile

Build/lib/create-file.ts:13–55

(span: Span, linesA: string[], filePath: string)

export const fileEqual = createCompareSource(fileEqualWithCommentComparator);

export async function compareAndWriteFile(span: Span, linesA: string[], filePath: string) {
  // readFileByLine will not include last empty line. So we always pop the linesA for comparison purpose
  if (linesA.length > 0 && linesA[linesA.length - 1] === '') {
    linesA.pop();
  }

  const isEqual = await span.traceChildAsync(`compare ${filePath}`, async () => {
    if (fs.existsSync(filePath)) {
      return fileEqual(linesA, readFileByLine(filePath));
    }

    console.log(`${filePath} does not exists, writing...`);
    return false;
  });

  if (isEqual) {
    console.log(picocolors.gray(picocolors.dim(`same content, bail out writing: ${filePath}`)));
    return;
  }

  return span.traceChildAsync<void>(`writing ${filePath}`, async () => {
    const linesALen = linesA.length;

    // The default highwater mark is normally 16384,
    // So we make sure direct write to file if the content is
    // most likely less than 250 lines
    if (linesALen < 250) {
      return writeFile(filePath, fastStringArrayJoin(linesA, '\n'));
    }

    const writeStream = fs.createWriteStream(filePath);
    for (let i = 0; i < linesALen; i++) {
      const p = asyncWriteToStream(writeStream, linesA[i] + '\n');
      // eslint-disable-next-line no-await-in-loop -- stream high water mark
      if (p) await p;
    }
    await new Promise<void>(resolve => {
      // Since we previously poped the last empty line for comparison, we need to add it back here to ensure final EOF line
      writeStream.end(resolve);
    });
    await promisify(writeStream.close.bind(writeStream))();
  });
}