[ruby-core:82635] [Ruby trunk Feature#13667][Feedback] Add Coverage.running? to quickly check if Coverage is enabled.

Issue #13667 has been updated by mame (Yusuke Endoh).

Status changed from Closed to Feedback

I applied the patch proposed.  After that, however, I'm now considering reverting it.

I noticed that this feature may be dangerous.  By using this, we can easily write a program that changes its behavior only under coverage measurement.  It brings difficulties to testing with coverage measurement.  I don't see such a bad program released into the wild.

Could you elaborate your use case that beats the disadvantage?  If any, I will remain the feature, but otherwise, I will revert it.

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Feature #13667: Add Coverage.running? to quickly check if Coverage is enabled.
https://bugs.ruby-lang.org/issues/13667#change-66462

* Author: burke (Burke Libbey)
* Status: Feedback
* Priority: Normal
* Assignee: mame (Yusuke Endoh)
* Target version: 
----------------------------------------
Since we can't `RubyVM::InstructionSequence#to_binary` when `Coverage` is running, it is useful to be able to ask ruby if coverage is active.

This is possible with `Coverage.peek_result`, but not efficient, since it involves quite a bit of data copying.

I've used the private symbol `rb_get_coverages` in [bootsnap](https://github.com/Shopify/bootsnap/pull/63) for now but this feels worth exposing publicly.

```
> Benchmark.realtime { 100.times{ Coverage.peek_result } }
=> 1.3659249999909662
> Benchmark.realtime { 100.times{ Bootsnap::CompileCache::Native.coverage_running? } }
=> 5.099998088553548e-05
```

Example usage:

```
class RubyVM::InstructionSequence
  def load_iseq(path)
    return nil if defined?(Coverage) && Coverage.running?
    # ...
  end
end
```

---Files--------------------------------
0001-Add-Coverage.enabled-to-quickly-check-if-coverage-is.patch (1.97 KB)


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