Add linter_level Attribute to Linter()

[AshesITR]

fixes #2351

system.time(lint_package())

# here
#   user  system elapsed 
# 76.062   0.196  76.302 

# main
#   user  system elapsed 
# 85.855   0.126  86.092 

[MichaelChirico]

FYI I won't be available for detailed review for some days

[AshesITR]

Thanks for the heads-up

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9e5b4ac) 99.41% compared to head (144bad1) 99.41%.

❗ Current head 144bad1 differs from pull request most recent head 9022725. Consider uploading reports for the commit 9022725 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2352   +/-   ##
=======================================
  Coverage   99.41%   99.41%           
=======================================
  Files         124      124           
  Lines        5642     5654   +12     
=======================================
+ Hits         5609     5621   +12     
  Misses         33       33           

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[IndrajeetPatil]

This looks great! Definitely an appreciable speed-up.

(I've a nitpicky comment, but don't feel strongly either way.)

[MichaelChirico]

NB:

match.arg(NA, NA_character_)
# Error in match.arg(NA, NA_character_) : 
#   'arg' must be NULL or a character vector

Maybe match.arg(as.character(linter_level)) is better?

[AshesITR]

Note that can omit linter_level= if you want NA. But yes, would be nicer to allow logical NA as well.