Let File::NULL ("/dev/null", "NUL" etc.) be considered a nil log device

[methodmissing]

References erroneous upstream PR ruby/ruby#2989

I noticed on a Logger instance with File::NULL or /dev/null as log device arguments a lot of formatting and other overhead still occurs, with the expected result essentially still being "I want to blackhole these logs":

GC: 130 (7.40%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       348  (19.8%)         348  (19.8%)     Logger::Formatter#format_datetime
       614  (35.0%)         169   (9.6%)     Logger::Formatter#call
       395  (22.5%)         152   (8.7%)     Logger::LogDevice#write

The logger was configured as Logger.new(File::NULL).

[sonots]

lgtm

[sonots]

hmm, ci failed. could you check?

[methodmissing]

Yep, already did https://travis-ci.com/github/ruby/logger/jobs/306798582 , a lot of tests are failing around this warning being spewed to stderr:

 1. [2/2] Assertion for "stderr"
     | <[]> expected but was
     | <["/Users/travis/build/ruby/logger/lib/logger/version.rb:4: warning: already initialized constant Logger::VERSION",
     |  "/Users/travis/.rvm/rubies/ruby-2.6.3/lib/ruby/2.6.0/logger.rb:227: warning: previous definition of VERSION was here"]>.
     | 

[methodmissing]

I think it references https://github.com/ruby/logger/pull/44/files - Logger::VERSION referenced from this core extraction, but the constant is loaded from the host ruby environment already (2.6.3 in this case)

🐔 and 🥚 problem

[sonots]

thanks, looks not related with this PR. I am going to merge this