Bug in as.data.frame.lints() [patch]

[fangly]

Still following the tutorial at https://cran.r-project.org/web/packages/lintr/vignettes/creating_linters.html

A Lint object is created as:

Lint(
  filename = source_file$filename,
  line_number = parsed$line1,
  column_number = parsed$col1,
  type = "style",
  message = "Use <-, not =, for assignment.",
  line = source_file$lines[parsed$line1]
  )

According to the help page for Lint, the linter parameter appears optional:

Lint(filename, line_number = 1L, column_number = NULL, type = c("style",
  "warning", "error"), message = "", line = "", ranges = NULL,
  linter = NULL)

All good then!

Except that further down the line when executing lint() with a small test case, I get an error message:

 Error in vapply(x, `[[`, character(1), "linter") : 
  values must be length 1,
 but FUN(X[[1]]) result is length 0 
10. vapply(x, `[[`, character(1), "linter") 
9. data.frame(filename = vapply(x, `[[`, character(1), "filename"), 
    line_number = vapply(x, `[[`, numeric(1), "line_number"), 
    column_number = vapply(x, `[[`, numeric(1), "column_number"), 
    type = vapply(x, `[[`, character(1), "type"), message = vapply(x,  ... 
8. as.data.frame.lints(lints) 
7. as.data.frame(lints) 
6. exclude(lints, ...) 
5. lint("./R/try_style.R", linters = semicolon_linter) at debugme.R#2
4. eval(substitute(expr), envir, enclos) 
3. evalq({
    library(lintr)
    lint("./R/try_style.R", linters = semicolon_linter)
}, envir = envir) at debugme.R#1
2. env$fun() 
1. debugSource("C:/qc/zoe_home/S001_BaseKit/debugme.R")

The problem is that as.data.frame.lints should accept a linter value of NULL but doesn't.

A small example reproduces the crash:

lints <- structure(list(Lint(
   filename = "xyz",
   line_number = 1,
   column_number = 10,
   type = "style",
   message = "Use <-, not =, for assignment.",
   line = "asdfasdfasdfasdf"
   )), class = "lints")
lintr:::as.data.frame.lints(lints)

If you add a "linter = 'my_linter'", then there is no crash anymore.

Cheers,
Florent

[fangly]

I guess since other text arguments to Lint() default to "" and not NULL, "linter" should also default to "".
Here is a patch that implements this fix (with some added tests, of course):
0001-Changed-Lint-s-linter-default-to-prevent-as.data.fra.patch.zip

[fangly]

This was fixed in the Lint() function by giving "linter" the default value "" (commit ae2870d).