Script that merges Cobertura coverage reports generated by Jest in an Nx monorepo and improves them for use in Azure DevOps

merge-cobertura-reports.mjs

import fs from 'fs/promises';
import { readdirSync, statSync } from 'fs';
import path from 'path';
import { promisify } from 'util';
import { exec as callbackExec } from 'child_process';

const exec = promisify(callbackExec);

const COVERAGE_DIR = path.resolve(process.cwd(), 'coverage');
const OUTPUT_DIR_RELATIVE = 'coverage';
const COBERTURA_FILENAME = 'cobertura-coverage.xml';
const COBERTURA_MERGED_FILENAME = 'cobertura-coverage-complete.xml';
const COBERTURA_TARGET_PATH = path.join(
  OUTPUT_DIR_RELATIVE,
  COBERTURA_MERGED_FILENAME,
);

// Recursive function to find all cobertura-coverage.xml files
// Using sync methods here as it simplifies the recursive structure slightly,
// and typically runs quickly enough during build processes.
function findCoberturaFilesRecursive(dir, files = []) {
  const list = readdirSync(dir);

  for (const file of list) {
    const absolutePath = path.join(dir, file);
    if (statSync(absolutePath).isDirectory()) {
      // Exclude the potential output directory itself to avoid self-inclusion
      if (absolutePath !== path.resolve(process.cwd(), OUTPUT_DIR_RELATIVE)) {
        findCoberturaFilesRecursive(absolutePath, files);
      }
    } else if (path.basename(absolutePath) === COBERTURA_FILENAME) {
      // Store path relative to CWD for the command
      files.push(path.relative(process.cwd(), absolutePath));
    }
  }
  return files;
}

async function mergeCoberturaFiles() {
  console.log(
    `Searching for ${COBERTURA_FILENAME} files in ${COVERAGE_DIR}...`,
  );

  let allCoberturaFiles = [];
  try {
    await fs.access(COVERAGE_DIR);
    allCoberturaFiles = findCoberturaFilesRecursive(COVERAGE_DIR);
  } catch (error) {
    if (error.code === 'ENOENT') {
      console.log('Coverage directory not found. Skipping merge.');
      return;
    } else {
      console.error('Error accessing coverage directory:', error);
      throw error;
    }
  }

  if (allCoberturaFiles.length === 0) {
    console.log('No Cobertura coverage files found to merge.');
    return;
  }

  console.log(`Found ${allCoberturaFiles.length} files to merge:`);
  allCoberturaFiles.forEach((file) => console.log(` - ${file}`));

  const targetDir = path.dirname(COBERTURA_TARGET_PATH);
  try {
    await fs.mkdir(targetDir, { recursive: true });
  } catch (err) {
    console.error(`Error creating target directory ${targetDir}:`, err);
    return;
  }

  const commandPrefix = `npx cobertura-merge -o ${COBERTURA_TARGET_PATH}`;
  const allPackagesCommand = allCoberturaFiles
    .map((file) => {
      const reportDir = path.dirname(file);
      const relativeProjectPath = path.relative(OUTPUT_DIR_RELATIVE, reportDir);
      const packageName =
        relativeProjectPath === '.'
          ? 'root'
          : relativeProjectPath.replace(/[/]/g, '.');
      const safePackageName = packageName || 'unknown';
      return `${safePackageName}=${file}`;
    })
    .join(' ');
  const completeCommand = `${commandPrefix} ${allPackagesCommand}`;

  console.log('\nRunning merge command:');
  console.log(completeCommand);

  try {
    const { stdout, stderr } = await exec(completeCommand);
    if (stderr) {
      console.error('Merge command stderr:', stderr);
    }
    console.log('Merge command stdout:', stdout);
    console.log(
      `\nSuccessfully merged Cobertura reports into ${COBERTURA_TARGET_PATH}`,
    );
  } catch (err) {
    console.error('\nError executing Cobertura merge command:', err);
    process.exit(1);
  }
}

mergeCoberturaFiles();