Add potential sequence() lints to seq_linter()

[Bisaloo]

Fix #2595

[MichaelChirico]

I think sequence() is not a very well-known function (<500 calls on CRAN vs more than 80K for seq()), here is a good opportunity to quickly introduce it:

"to use the sequence() function, e.g. unlist(lapply(ints, seq))"

[MichaelChirico]

nit: I would try and keep the logic in one direction on the AST: check sapply, then check seq_len, then check unlist, roughly

//SYMBOL_FUNCTION_CALL/parent::expr[following-sibling::expr/SYMBOL]/parent::expr/parent::expr[expr/SYMBOL_FUNCTION_CALL]

Also, please switch to use the new find_function_calls approach, which is appropriate here, e.g.

lintr/R/condition_call_linter.R

Line 83 in 6ed78c2

xml_calls <- source_expression$xml_find_function_calls(c("stop", "warning"))

[MichaelChirico]

The lint now only covers unlist(lapply(x, seq_len)).

What about

• unlist(lapply(x, seq))
• unlist(lapply(x, seq, by = 2)), and other variants equivalent to using the from= and/or by= arguments of sequence()?
• I don't think it's worth trying to find examples like lapply(x, \(xi) seq(xi)) which would be covered by unnecessary_lambda_linter(). But are there any examples that do require looking into a lambda to replicate a sequence()-able call?

(it would be nice to get a sense of how many hits these are getting before investing too much time -- and also feel free to earmark some of this as a TODO in a follow-up issue, though lapply(x,seq) is trivial enough to be done here)

[Bisaloo]

unlist(lapply(x, seq, by = 2)), and other variants equivalent to using the from= and/or by= arguments of sequence()?

I don't think there is a direct equivalence:

• from has a different behaviour in seq() and sequence()

  unlist(lapply(1:5, seq, from = 2))
  #>  [1] 2 1 2 2 3 2 3 4 2 3 4 5
  
  sequence(1:5, from = 2)
  #>  [1] 2 2 3 2 3 4 2 3 4 5 2 3 4 5 6

  ^{Created on 2024-06-22 with reprex v2.1.0}

• As far as I can tell, by= cannot be used on its own without from=, which brings us back to the previous case

  seq(20, by = 2)
  #> Error in seq.default(20, by = 2): wrong sign in 'by' argument

  ^{Created on 2024-06-22 with reprex v2.1.0}

I have edited the xpath to make sure this type of call doesn't lint.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.97%. Comparing base (fc2268f) to head (072ef13).
Report is 19 commits behind head on main.

❗ Current head 072ef13 differs from pull request most recent head 2a8d243

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2618      +/-   ##
==========================================
- Coverage   98.15%   97.97%   -0.18%     
==========================================
  Files         125      126       +1     
  Lines        5738     5774      +36     
==========================================
+ Hits         5632     5657      +25     
- Misses        106      117      +11     

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[IndrajeetPatil]

Let's also wait for MC's approval.

@MichaelChirico Can we add @Bisaloo to the repo as a contributor? Of course, only if he wishes to. 😅