Meteor 3.3.x and meteortesting:mocha/lmieulet:meteor-coverage

help
1

Hi,

I have issue using meteortesting:mocha/lmieulet:meteor-coverage whith meteor@3.3.x when modern: true

With modern: false, it works well but with modern: true, i have the following error (all tests passed but the coverage not):

W20250909-10:14:44.909(2)? (STDERR) Error: Failed to save lcovonly coverage. 500 [object Object]
W20250909-10:14:44.910(2)? (STDERR)     at packages/meteortesting:mocha/server.handleCoverage.js:21:11
W20250909-10:14:44.910(2)? (STDERR)     at Generator.next (<anonymous>)
W20250909-10:14:44.910(2)? (STDERR)     at asyncGeneratorStep (/tmp/meteor-test-run1j4ree.uzqzq/.meteor/local/build/programs/server/packages/meteortesting_mocha.js:280:28)
W20250909-10:14:44.910(2)? (STDERR)     at _next (/tmp/meteor-test-run1j4ree.uzqzq/.meteor/local/build/programs/server/packages/meteortesting_mocha.js:298:17)
W20250909-10:14:44.910(2)? (STDERR)     at processTicksAndRejections (node:internal/process/task_queues:105:5)

The command line is the following :

MONGO_URL='' BABEL_ENV=test TEST_CLIENT=0 NO_HMR=1 COVERAGE=1 COVERAGE_OUT_LCOVONLY=1 COVERAGE_APP_FOLDER=$PWD/ meteor test --once --driver-package meteortesting:mocha

Thanks.

2

I’d appreciate it if you could prepare a minimal repo for this. Matching your config is tricky. Having one would save a lot of time so I can focus on the fix.

For SWC, we may need to use it with kwonoj/swc-plugin-coverage-instrument. Having an example repository will allow me to play with it and provide a skeleton for everyone.

3

Thanks. Here a minimal repo :

meteor run then meteor npm run test and you get the error.

4

looking at packages/meteortesting:mocha/server.handleCoverage.js:21:11 error :

I20250910-16:46:09.190(2)?     url: 'http://localhost:3000/coverage/export/lcovonly',
I20250910-16:46:09.190(2)?     status: 500,
I20250910-16:46:09.190(2)?     statusText: 'Internal Server Error',
I20250910-16:46:09.190(2)?     headers: Headers { [Symbol(map)]: [Object: null prototype] },
I20250910-16:46:09.190(2)?     counter: 0
I20250910-16:46:09.191(2)?   }
I20250910-16:46:09.191(2)? }
I20250910-16:46:09.191(2)? data: { type: 'No coverage to export' }
I20250910-16:46:09.191(2)? url: /coverage/export/lcovonly
I20250910-16:46:09.191(2)? message: Failed to save lcovonly coverage.

it seems there is no more instrumentation made by babel-plugin-istanbul

5

Yeah, because with "modern": true, we use SWC as the transpiler. The reason way I was suggesting to incorporate kwonoj/swc-plugin-coverage-instrument. if you can play with it, go ahead and let us know what you get. I will when I have free time.

6

It was my next step :wink:

So, I removed babel-plugin-istanbul and installed GitHub - kwonoj/swc-plugin-coverage-instrument: istanbuljs compatible SWC coverage instrumentation plugin.
I configured it in swc.config.js as documented.

And now, everything works well. Coverage is back.

Thanks.

7

Aha, great! Could you push the changes?

They can serve as a good example for others adopting modern SWC and have test coverage. Maybe we could also open a PR on lmieulet:meteor-coverage to update the docs and mention this step and point to your changes for those using Meteor modern build stack.

8

Sure.

in package.json, set modern: true

meteor npm remove -D babel-plugin-istanbul
meteor npm i -D swc-plugin-coverage-instrument

in the file swc.config.js:

module.exports = {
  jsc: {
    baseUrl: './',
    experimental: {
      plugins: [
        [
          'swc-plugin-coverage-instrument',
          {
            unstableExclude: [
              '**/node_modules/**',
              '**/.meteor/**',
              '**/packages/**',
              '**/tests/**',
            ],
          },
        ],
      ],
    },
  },
};

run your tests and you should have your coverage. At least, this setup works for me.

9

I found only a specific version of swc-plugin-coverage-instrument works:

swc-plugin-coverage-instrument@0.0.28

not:

swc-plugin-coverage-instrument@0.0.26
or
swc-plugin-coverage-instrument@0.0.32 (the latest)

At least those two versions crash!

10

Which rspack and Meteor version have you ?

11

Meteor 3.3.2 with modern=true

12

Unless I am mistaken, Meteor 3.3.2 uses swc 1.12.14 so swc_core is 32.0.2.

sw_core dependency for swc-plugin-coverage-instrument@0.0.32 is 47.0.3 So it will not work.

Correct @nachocodoner ?

13

Yes, you’re right.

Meteor 3.3.2 is fixed to use @swc/core 1.12.14 through a custom NPM package.

With the latest Meteor 3.4-rc.1 I bumped the internal Meteor SWC version to 1.15.3, which uses swc_core v48.0.2, likely compatible with swc-plugin-coverage-instrument@0.0.32.

Upgrading to Meteor 3.4-rc.1 won’t force you to use the Rspack integration, so you can update and still use the Meteor bundler alone. Besides this, I want to mention that adopting Rspack for your app code will make your setup depend on Rspack, which updates SWC on its own schedule.

14

Could any of you help me out?

I made the changes mentioned by @harry73 about swc, however, I’m getting a 500 error. I’m not sure how to proceed

 Export code coverage
 - Out html
 [coverage] export coverage using the following format [ html ] options [ {
   path: '/home/ferjep/yourdnafamily/octopussy/.coverage',
   verbose: true
 } ]
 Write asset: ./base.css
 Write asset: ./block-navigation.js
 Write asset: ./sort-arrow-sprite.png
 Write asset: ./sorter.js
 Write asset: ./prettify.css
 Write asset: ./prettify.js
 (STDERR) Error: Failed to save html report. 500 [object Object]
 (STDERR)     at request (packages/meteortesting:mocha/server.handleCoverage.js:21:11)
 (STDERR)     at processTicksAndRejections (node:internal/process/task_queues:105:5)
 [coverage] export coverage using the following format [ http ] options [ {
   path: '/home/ferjep/yourdnafamily/octopussy/.coverage',
   verbose: true,
   filepath: undefined
 } ]

This is how I’m running it

COVERAGE=1 COVERAGE_VERBOSE=1 COVERAGE_APP_FOLDER=$PWD/ TEST_WATCH=1 COVERAGE_OUT_HTML=1 meteor test --driver-package meteortesting:mocha --settings settings-development.json

package.json (meteor only)

  "meteor": {
    "modern": {
      "transpiler": {
        "verbose": false
      }
    },
    "mainModule": {
      "client": "client/main.js",
      "server": "server/main.js"
    }
  },
15

Hi,

Which Meteor and swc-plugin-coverage-instrument version do you run?

16

Meteor 3.3.2 and swc-plugin-coverage-instrument 0.0.32

17

try with swc-plugin-coverage-instrument 0.0.28

18

It gets worse I think. I get code errors now

error on boot.js /tmp/meteor-test-run1q6cxtm.302vl/.meteor/local/build/programs/server/app/app.js:107086
const ANDME_FORMAT = (cov_16790224454079739546().s[4]++, await getFormat(‘andme’, ‘v4’, undefined));
^^^^^^^^^

SyntaxError: Unexpected identifier ‘getFormat’
at new Script (node:vm:117:7)
at createScript (node:vm:269:10)
at Object.runInThisContext (node:vm:317:10)
at /tools/static-assets/server/boot.js:414:32
at /tools/static-assets/server/boot.js:502:11
at Function.run (/tmp/meteor-test-run1q6cxtm.302vl/.meteor/local/build/programs/server/tools/tool-env/profile.ts:651:14)
at startServerProcess (/tools/static-assets/server/boot.js:501:17)
at Object. (/tools/static-assets/server/boot.js:506:2)
at Object. (/tools/static-assets/server/boot.js:510:4)
at Module. (node:internal/modules/cjs/loader:1688:14)
at Module.Mp._compile (/tools/static-assets/server/runtime.js:91:21)
at Object.Module._extensions..js (/tools/static-assets/server/runtime.js:125:21)
at Module. (node:internal/modules/cjs/loader:1423:32)
at Module.Mp.load (/tools/static-assets/server/runtime.js:35:31)
at Function._load (node:internal/modules/cjs/loader:1246:12)
at TracingChannel.traceSync (node:diagnostics_channel:322:14)
/tmp/meteor-test-run1q6cxtm.302vl/.meteor/local/build/programs/server/app/app.js:107086

19

@nachocodoner Could you help me somehow?

I have 2 projects with kind of the same set up and have the same 500 error

20

Have you tried using the Meteor 3.4-rc.1 version I mentioned above, which bumps SWC to the latest and should include a swc_core version compatible with swc-plugin-coverage-instrument@0.0.32?

If not, and to help you further, I’d need a bit more to reproduce your issue. Could you provide a minimal reproduction repository where I can quickly see the problem and explore a fix?