Can I merge multiple coverage reports across an Nx Angular mono repo?

Question

I have Jenkins building our nx Angular mono repo. Right now, each app/module produces its own report under the coverage directory. Is there an approved way or a good way to merge all those reports into a single html report?

Answer 1

istanbul-combine will be deprecated in favor of istanbul report. I did a migration lately.

This was the old configuration that I was using with istanbul-combine:

istanbul-combine -d coverage -p none -r lcov -r cobertura coverage/hierarchical-grid/coverage-final.json coverage/tree-grid/coverage-final.json coverage/non-grid/coverage-final.json coverage/grid/coverage-final.json

Changed to:

istanbul report --dir coverage --include coverage/**/coverage-final.json lcov

I was searching for a way to combine a couple .json reports with GitHub Actions CI.

The good side of this configuration above is that all .json files are part of similar directories:

• coverage/grid/coverage-final.json
• coverage/non-grid/coverage-final.json etc.

This is where the lcov report would be generated:

Related Pull Request.

Answer 2

I've had the same problem myself. After running into this demand in 3 different projects, I've decided to write a blog post about it: https://yonatankra.com/how-to-create-a-workspace-coverage-report-in-nrwl-nx-monorepo/

In essence, I've written a script that takes the lcov files and combines them:

const glob = require('glob');
const fs = require('fs');
const path = require('path');

const getLcovFiles = function (src) {
  return new Promise((resolve, reject) => {
    glob(`${src}/**/lcov.info`, (error, result) => {
      if (error) return reject(error);
      resolve(result);
    });
  })
};

(async function(){
  const files = await getLcovFiles('coverage');
  const mergedReport = files.reduce((mergedReport, currFile) => mergedReport += fs.readFileSync(currFile), '');
  await fs.writeFile(path.resolve('./coverage/lcov.info'), mergedReport, (err) => {
    if (err) throw err;
    console.log('The file has been saved!');
  });
})();

I then used it after the npm test script.

If you need the JSON format, you can use https://github.com/davglass/lcov-parse or some other converter after the merge.

Answer 3

istanbul-combine is the best solution I've found for this. It uses an old version of istanbul internally, but it worked for me.

Answer 4

One possibility I found was to create a simple script to take care of the job. Fully under your control, so you can keep it up2date. I could not find something that was perfect for my needs.

https://github.com/neekware/fullerstack/blob/main/tools/utils/coverageMerge.ts

I am still looking to have a way to send the individual coverage files for publishable libraries, to be sent to coveralls separately. Once the solution is found, I will update the script. For now, all public libs sadly have to use the overall combined coverage links.

Answer 5

Merging reports using the cobertura-merge library is another option (if you can use the cobertura reporting format), see here for a link to detailed step-by-step instructions https://stackoverflow.com/a/75614044/18727037

The linked blog article also includes instructions on integrating the merged coverage results into a Gitlab CI/CD pipeline. Maybe you can apply some of that to your jenkins pipeline.