Coverage reports don't include TS files unless explicitly compiled

[lumaxis]

Expected Behavior

When running nyc with mocha which is using ts-node to transpile TypeScript files on the fly, TypeScript files should be part of the coverage report.

Observed Behavior

nyc is only generating coverage output for the only .js file in my project:

-------------|----------|----------|----------|----------|----------------|
File         |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
-------------|----------|----------|----------|----------|----------------|
All files    |    52.37 |    29.71 |    75.61 |    52.37 |                |
 file.js     |    52.37 |    29.71 |    75.61 |    52.37 |... 759,764,766 |
-------------|----------|----------|----------|----------|----------------|

=============================== Coverage summary ===============================
Statements   : 52.37% ( 210/401 )
Branches     : 29.71% ( 71/239 )
Functions    : 75.61% ( 31/41 )
Lines        : 52.37% ( 210/401 )

It however works when I first manually compile all my files using tsc and then it even shows the actual .ts files, not only the .js files.

Forensic Information

Operating System: macOS 10.13.1
Environment Information: https://gist.github.com/lumaxis/cd33c2bbf98dab6e4f5dcc9ff6bf5984

.nycrc

{
    "all": true,
    "cache": false,
    "exclude": [
        "coverage",
        "**/editor.js",
        "**/gulpfile.js",
        "**/tasks.js",
        "**/test/**",
        "**/*_test.js"
    ],
    "extensions": [
        ".js",
        ".ts"
    ],
    "report-dir": "./coverage",
    "reporter": [
        "cobertura",
        "html",
        "text",
        "text-summary"
    ],
    "temp-directory": "./coverage/.nyc_output"
}

mocha.opts

--exit
--reporter spec
--require dotenv/config
--require ts-node/register
--slow 200
--timeout 4000

[lumaxis]

I think I solved this by reducing the config file to

{
    "cache": true,
    "extensions": [
        ".ts"
    ],
    "report-dir": "./coverage",
    "reporter": [
        "cobertura",
        "html",
        "text",
        "text-summary"
    ],
    "temp-directory": "./coverage/.nyc_output"
}

Especially removing "all": true and "extensions": [ ".js" ] seemed to be important. Not sure why it is mentioned in https://istanbul.js.org/docs/tutorials/typescript/ but it appears I need neither them nor source-map-support/register to get a working mocha & TypeScript setup.

[bcoe]

Please see microsoft/TypeScript#24993, I'm interested in overhauling our TypeScript support and would love your feedback and requirements.

[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.

[kleinfreund]

@lumaxis The extension configuration key for nyc is extension, not extensions which is very confusing. Could you update your posts so that other people have a chance to solve this issue, please?

[lumaxis]

@kleinfreund Wow 🤦🏼‍♂️ I never noticed that …
It might be that none of what I wrote above is actually valid anymore of I were to repeat it with the changed object key, so not sure editing my original post is very helpful in that way.
Unfortunately, I don't currently work on a project using istanbul/nyc anymore so I can't easily verify my issue.

[kleinfreund]

@lumaxis Oh, it is relevant. I need the following in my package.json for nyc to recognize the TypeScript source files I’m testing with ava.

"nyc": {
  "extension": [
    ".ts"
  ]
}

[lumaxis]

Sure, that's still valuable information but I don't think it's wise for me to edit my original post.
If I edit my example, my described results would not reproduce anymore.

[bcoe]

@kleinfreund seems like maybe we could add another tutorial to https://istanbul.js.org/ and/or a note in the README about needing to support .ts extensions?

I'd argue this specific issue can be closed though; want to go ahead and open an issue if you think it's worthwhile, or heck, would happily take a pull request.

[JaKXz]

@lumaxis would you mind trying something like this? istanbuljs/istanbuljs#282