Add potential sequence() lints to seq_linter() (#2618)

* Draft sequence_linter linter

* Fold sequence_linter() into seq_linter()

* Add tests

* Add NEWS bullet

* Switch to xml_find_function_calls

* Change element order in xpath

* Support lapply(x, seq)

* Simplify xpath

* Do not lint seq() calls with extra arguments

* Edit false positive example

* Add more info about new lints in NEWS

* update

* Update NEWS.md

* add Hugo to DESCRIPTION (and clean it up)

* change DESCRIPTION --> change Rd

---------

Co-authored-by: Michael Chirico <[email protected]>
Co-authored-by: Michael Chirico <[email protected]>

Author: Bisaloo

DESCRIPTION

@@ -4,14 +4,17 @@ Version: 3.2.0.9000
 Authors@R: c(
     person("Jim", "Hester", , role = "aut"),
     person("Florent", "Angly", role = "aut",
-           comment = "fangly"),
+           comment = c(GitHub = "fangly")),
     person("Russ", "Hyde", role = "aut"),
-    person("Michael", "Chirico", email = "[email protected]", role = c("aut", "cre")),
+    person("Michael", "Chirico", email = "[email protected]", role = c("aut", "cre"),
+           comment = c(ORCID = "0000-0003-0787-087X")),
     person("Kun", "Ren", role = "aut"),
     person("Alexander", "Rosenstock", role = "aut",
-           comment = "AshesITR"),
-    person("Indrajeet", "Patil", , "[email protected]", role = "aut",
-           comment = c(ORCID = "0000-0003-1995-6531", Twitter = "@patilindrajeets"))
+           comment = c(GitHub = "AshesITR")),
+    person("Indrajeet", "Patil", email = "[email protected]", role = "aut",
+           comment = c(ORCID = "0000-0003-1995-6531", Twitter = "@patilindrajeets")),
+    person("Hugo", "Gruson", role = "aut",
+           comment = c(ORCID = "0000-0002-4094-1476"))
   )
 Description: Checks adherence to a given style, syntax errors and possible
     semantic issues.  Supports on the fly checking of R code edited with

NEWS.md

@@ -20,7 +20,9 @@
 ## New and improved features
 
 * `brace_linter()`' has a new argument `function_bodies` (default `"multi_line"`) which controls when to require function bodies to be wrapped in curly braces, with the options `"always"`, `"multi_line"` (only require curly braces when a function body spans multiple lines), `"not_inline"` (only require curly braces when a function body starts on a new line) and `"never"` (#1807, #2240, @salim-b).
-* `seq_linter()` recommends using `seq_along(x)` instead of `seq_len(length(x))` (#2577, @MichaelChirico).
+* `seq_linter()`:
+   + recommends using `seq_along(x)` instead of `seq_len(length(x))` (#2577, @MichaelChirico).
+   + recommends using `sequence()` instead of `unlist(lapply(ints, seq))` (#2618, @Bisaloo)
 * `undesirable_operator_linter()` lints operators in prefix form, e.g. `` `%%`(x, 2)`` (#1910, @MichaelChirico). Disable this by setting `call_is_undesirable=FALSE`.
 * `indentation_linter()` handles `for` un-braced for loops correctly (#2564, @MichaelChirico).
 * Setting `exclusions` supports globs like `knitr*` to exclude files/directories with a pattern (#1554, @MichaelChirico).

R/seq_linter.R

@@ -32,6 +32,11 @@
 #'   linters = seq_linter()
 #' )
 #'
+#' lint(
+#'   text = "unlist(lapply(x, seq_len))",
+#'   linters = seq_linter()
+#' )
+#'
 #' # okay
 #' lint(
 #'   text = "seq_along(x)",
@@ -53,6 +58,11 @@
 #'   linters = seq_linter()
 #' )
 #'
+#' lint(
+#'   text = "sequence(x)",
+#'   linters = seq_linter()
+#' )
+#'
 #' @evalRd rd_tags("seq_linter")
 #' @seealso [linters] for a complete list of linters available in lintr.
 #' @export
@@ -80,6 +90,17 @@ seq_linter <- function() {
     parent::expr[expr/expr/SYMBOL_FUNCTION_CALL[text() = 'length']]
   "
 
+  map_funcs <- c("sapply", "lapply", "map")
+  seq_funcs <- xp_text_in_table(c("seq_len", "seq"))
+  # count(expr) = 3 because we only want seq() calls without extra arguments
+  sequence_xpath <- glue("
+    parent::expr[
+      count(expr) = 3
+      and expr/SYMBOL[ {seq_funcs} ]
+      and preceding-sibling::expr/SYMBOL_FUNCTION_CALL[text() = 'unlist']
+    ]
+  ")
+
   ## The actual order of the nodes is document order
   ## In practice we need to handle length(x):1
   get_fun <- function(expr, n) {
@@ -138,6 +159,15 @@ seq_linter <- function() {
       type = "warning"
     )
 
-    c(seq_lints, seq_len_lints)
+    xml_map_calls <- source_expression$xml_find_function_calls(map_funcs)
+    potential_sequence_calls <- xml_find_all(xml_map_calls, sequence_xpath)
+    sequence_lints <- xml_nodes_to_lints(
+      potential_sequence_calls,
+      source_expression,
+      "Use sequence() to generate a concatenated sequence of seq_len().",
+      type = "warning"
+    )
+
+    c(seq_lints, seq_len_lints, sequence_lints)
   })
 }

man/lintr-package.Rd

@@ -123,6 +123,24 @@ test_that("reverse seq is ok", {
   )
 })
 
+test_that("finds potential sequence() replacements", {
+  linter <- seq_linter()
+  lint_msg <- rex::rex("Use sequence()")
+
+  expect_lint("unlist(lapply(x, seq_len))", lint_msg, linter)
+
+  expect_lint("unlist(lapply(x, seq))", lint_msg, linter)
+
+  # Even for prefixed purrr:: calls
+  expect_lint("unlist(purrr::map(x, seq_len))", lint_msg, linter)
+})
+
+test_that("sequence() is not recommended for complex seq() calls", {
+  linter <- seq_linter()
+
+  expect_no_lint("unlist(lapply(x, seq, from = 2))", linter)
+})
+
 test_that("Message vectorization works for multiple lints", {
   linter <- seq_linter()
 
@@ -173,6 +191,18 @@ test_that("Message vectorization works for multiple lints", {
     ),
     linter
   )
+
+  expect_lint(
+    trim_some("{
+      1:NROW(x)
+      unlist(lapply(y, seq_len))
+    }"),
+    list(
+      list(rex::rex("seq_len(NROW(...))", anything, "1:NROW(...)"), line_number = 2L),
+      list(rex::rex("sequence()"), line_number = 3L)
+    ),
+    linter
+  )
 })
 
 test_that("Message recommends rev() correctly", {