Broken HTML report when merging coverage info with nyc report

[bennycode]

Link to bug demonstration repository.

• https://github.com/bennyn/typescript-jasmine-karma-nyc

Expected Behavior

HTML report where you can click on files to see their code coverage.

Observed Behavior

HTML report which is broken for some of the files:

TypeError: Cannot read property 'locations' of undefined

Scenario

• I wrote TypeScript code which behaves differently depending on the environment (Node.js or a HTML5 browser) it runs on.
• To test every part of my code, I need to run tests in a Browser environment and in a Node.js environment.
• For running tests in Node.js, I am using nyc in combination with jasmine and ts-node/register.
• Browser tests are performed by karma with karma-jasmine and karma-chrome-launcher.
• When I execute the browser tests in my project (yarn test:browser), I am getting HTML output (coverage/browser/html) and JSON output (coverage/json/coverage-browser.json). The HTML report works fine. I can see my TypeScript files in the report and their coverage.
• When I execute the Node.js tests in my project (yarn test:node), I am also getting HTML output (coverage/node/html) and JSON output (coverage/json/coverage-final.json). The HTML report looks fine here too!
• The code coverage of my browser tests report that half of my code is covered by tests.
• The code coverage of my Node.js tests report that the other half of my code is covered.

I would like to join both code coverage reports now to receive one universal (merged) report that states that my app code is fully covered by tests.

I have read documentation on nyc merge and thought it is a good idea to run nyc report (which implicitly merges coverage information) and point it to my JSON output files:

nyc report --temp-dir coverage/json --report-dir=coverage/merged/html --reporter=html

The nyc report command finishes and I am receiving an HTML report but the report is broken (see "Observed Behavior"). I would like to know what is going wrong there because when I check the individual HTML reports (coverage/browser/html & coverage/node/html) they look fine.

Forensic Information

Operating System: Windows 10 Pro (but I think the problem is unrelated to the OS)
Environment Information:

• Node.js v10.9.0
• npm v6.4.1

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[coreyfarrell]

Closing here in favor of istanbuljs/istanbuljs#322.

[filame]

I do not use karma and have the exact same issue with merging coverage files.
I use cypress and jest and want to merge their coverage outputs.
What happens is exactly what was described by @bennyn.

I use:

• jest 24.8.0
• cypress 3.4.1
• istanbul-lib-coverage 2.0.5
• nyc 14.1.1