fix: ignore lines have to be dropped from coverage and not to be included as covered

[anthony-redFox]

Html coverage report base on statementMap and s then if line doesn't exists will be marked 'neutral' by default.

It will be repeat behavior "istanbul ignore"

[anthony-redFox]

Also add new commit which will be ignore empty lines and JavaScript comments

[AriPerkkio]

Excluding the lines based on whitespace can be error prone. How does it report following case?

1 | function unCoveredFunction() {
2 |     const something = 1;
3 |
4 |     return something;
5 | }

Is line 3 marked as uncovered or excluded completely?

Maybe better approach would be to exclude all lines that are not present in source maps.

[anthony-redFox]

It will be excluded completely, so that mean you have 4 lines of code in report. (HTML report will marks as gray).

If you add more empty lines or comments then it is not effect on coverage report %

[AriPerkkio]

Detecting lines for exclusion with regular expression will be really difficult. There are so many ways to write Javascript. For example patterns below are not detected by the current implementation:

/* Line not excluded */ console.log()

/** Line not excluded

 * Line not excluded

 */ // Line not excluded

/* Line not excluded

Line not excluded

*/

console.log(`
// This line is excluded ${console.log("even though there's code running here!")}
`)

I still think it would be better to exclude lines based on whether they are present in source maps or not.