FunctionDeclarations default to a cover count of 1

[derek]

The following code will produce a coverage object that contains a line of coverage despite having never been executed.

var istanbul = require('istanbul'),
    instrumenter = new istanbul.Instrumenter();

instrumenter.instrumentSync('function foo() {};');
console.log(instrumenter.lastFileCoverage());

It appears this "bug" (debatable) was introduced in #67.

The reason why I feel this is a bug, and why I'm using the undocumented(?) instrumenter#lastFileCoverage method, is because I am attempting to generate a coverage object consumable by collector#add for code that I have no intention of actually executing. This is solely for reporting purposes, where I'd like files that are not executed by my unit tests to appear in the HTML report as having 0/0/0/0 coverage. But, if this capability is not supported, then I guess this wouldn't be considered a bug.

FWIW, ideally I'd like to pass a Collector or Reporter an array of paths I'd like to include in the report with zero coverage, but that would simply be sugar around existing capabilities.

[gotwarlost]

• The original implementation should never have considered function declarations as statements, since they are really not executed (but that would have caused a discrepancy with older tools that I was trying to get people to transition from)
• This then led to the issue that if the function declaration was just after a return statement, it would never be covered even if all the lines in the function are executed. I put in a "fix" to always consider function declarations as covered, so that this would not screw up people's existing metrics.
• And now you come along asking for 0/0/0 coverage. Rock meet hard place :)

Of course, the correct fix is to not consider declarations as statements at all but it will have the effect of lowering peoples' existing coverage numbers and is not backwards compatible.

Thinking on how best to deal with this... Ideas welcome.

[derek]

Considering both approaches seem valid, but at the same time conflict, perhaps this is a scenario where an additional config option to Instrumenter is appropriate?

In any case, this was pretty trivial to manually set all statement counts to zero, so it's not a big deal for me.

instrumenter.instrumentSync(fs.readFileSync(path, 'utf-8'), path);
uncovered[path] = instrumenter.lastFileCoverage();
for (i in uncovered[path].s) {
    uncovered[path].s[i] = 0;
}

So perhaps address this only if others request the capability as well.