[Bug] Branch coverage incorrect in async static class methods

[acodeninja]

Describe the bug

When using monocart coverage reports, branches inside static async class methods are shown as else uncovered when using monocart

To Reproduce

• Version:
  • monocart-coverage-report - 2.10.1
  • c8 - 10.1.2
• Node Version: 22.4.1
• Have you tried the latest version (including node), and does the issue still exist? yes
• Steps to reproduce the actual behavior:
  1. Write a simple class with a static async method containing an if statement (see reproduction)
  2. Write a straight forward test to cover the branch (see reproduction)
  3. Run the test with monocart coverage reports:

     ⇒ c8 --experimental-monocart node Uncovered.test.js
     --------------|---------|----------|---------|---------|-------------------
     File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
     --------------|---------|----------|---------|---------|-------------------
     All files     |     100 |       50 |     100 |     100 |                   
      Uncovered.js |     100 |       50 |     100 |     100 | 3                  
     --------------|---------|----------|---------|---------|-------------------

  4. Run the test without monocart coverage reports:

     ⇒ c8 node Uncovered.test.js                        
     --------------|---------|----------|---------|---------|-------------------
     File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
     --------------|---------|----------|---------|---------|-------------------
     All files     |     100 |      100 |     100 |     100 |                   
      Uncovered.js |     100 |      100 |     100 |     100 |                   
     --------------|---------|----------|---------|---------|-------------------

Expected behavior

In both instances the coverage should be 100% as all lines and branches are in fact covered.

Errors or Screenshots

Any captured error messages, or add screenshots to help explain your problem.

Make a minimal reproduction

package.json

{
  "type": "module",
  "dependencies": {
    "c8": "^10.1.2",
    "monocart-coverage-reports": "^2.10.1"
  }
}

Uncovered.js

export class Uncovered {
    static async uncovered(active) {
        if (active) throw new Error('Active');

        return !active;
    }
}

Uncovered.test.js

import * as assert from 'node:assert';
import {Uncovered} from './Uncovered.js';

assert.equal(await Uncovered.uncovered(false), true);

await assert.rejects(async () => Uncovered.uncovered(true), {
    name: 'Error',
});

Run the following:

npm install
c8 node Uncovered.test.js  # see the 100% coverage output
c8 --experimental-monocart node Uncovered.test.js  # see the 50% branch coverage output

Additional context

While this may be down to some strange interactions with c8 I was unable to trigger this behaviour in the normal c8 coverage checks.

I was unable to reproduce this issue with a normal named async or synchronous function:

async function uncovered(active) {
    if (active) throw new Error('Active');

    return !active;
}

I was unable to reproduce this issue with a synchronous static class method:

export class Uncovered {
    static uncovered(active) {
        if (active) throw new Error('Active');

        return !active;
    }
}

I was unable to reproduce this issue with an async instance method:

export class Uncovered {
    async uncovered(active) {
        if (active) throw new Error('Active');

        return !active;
    }
}

[acodeninja]

In my specific use case I've been able to work around this to achieve 100% branch coverage by moving the if statement into a synchronous static method on the class like so:

export class Uncovered {
    static checkActive(active) {
        if (active) throw new Error('Active');
    }
    static async uncovered(active) {
        this.checkActive(active);

        return !active;
    }
}

This then results in 100% branch coverage:

⇒ c8 --experimental-monocart node Uncovered.test.js
--------------|---------|----------|---------|---------|-------------------
File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
--------------|---------|----------|---------|---------|-------------------
All files     |     100 |      100 |     100 |     100 |                   
 Uncovered.js |     100 |      100 |     100 |     100 |                   
--------------|---------|----------|---------|---------|-------------------

[cenfun]

I can reproduce it simply with following

class StaticAsync {
    static async covered(active) {
        // should be covered
        if (active) {
            return 1;
        }
        return 2;
    }
}

await StaticAsync.covered(false);
await StaticAsync.covered(true);

It should be a issue related to static which is similar to #37 I will figure out how to fix it.

[cenfun]

Please try monocart-coverage-reports@2.10.2

[acodeninja]

Hi @cenfun I can confirm this has resolved the issue, thank you for sorting this out!