An illustration of how to write a "lintr" config file

.lintr

linters: with_defaults(
  # By using the `with_defaults` function in .lintr to set up the linters for your package / project,
  # you are telling {lintr}: start with this named-list of linters (given in the argument `default`,
  # see below) and modify any that I specify.
  # Here, that means you want to use the list `default_linters`, but modify that list.
  #
  # See `names(lintr::default_linters)` for the contents of the `default_linters` used here.
  #
  # You could alternatively
  #
  # - use all the linters in the `default_linters` without modification by using the line
  # `linters: default_linters`
  # - use a single linter (eg `no_tab_linter`) by using the line `linters: no_tab_linter`
  # 
  # in your .lintr file.
  #
  # What kind of modifications to the `default` list are allowed?
  #
  # {DROPPING A DEFAULT LINTER}
  #
  # To drop one of the named linters from the `default` list, you set the `linter-name = NULL`.
  # For example, if you don't want {lintr} to flag commented code:
  commented_code_linter = NULL,
  #
  # {MODIFYING A DEFAULT LINTER}
  #
  # To modify a parameterised linter (eg, closed_curly_linter, object_name_linter, object_length_linter),
  # you override the default parameter value. 
  # - `line_length_linter` has a default of 80, to extend this to allow 100-width lines do the following:
  line_length_linter = line_length_linter(100),
  #
  # - `object_length_linter` has a default object-name size of 30 characters, we can extend this to 40
  # characters
  # (note that you don't need to specify the name of the linter that you are overriding if it one of
  # the linters in the `default` list)
  object_length_linter(40),
  #
  # - `object_name_linter` has default "snake_case" - to allow newly-defined objects to have names that
  # are in either `snake_case` or `CamelCase` (typical for classes):
  object_name_linter = object_name_linter(c("snake_case", "CamelCase")),
  #
  # {ADDING A NON-DEFAULT LINTER}
  #
  # There are many linters that are not included in the `default_linters` used here.
  # If you want to prevent the use of `return`, `sapply`, or some other unsafe / unnecessary functions:
  undesirable_function_linter = undesirable_function_linter(),
  #
  # Note that `undesirable_function_linter` (and the related `undesirable_operator_linter`) is
  # parameterisable, so the parentheses are necessary in the last modification
  #
  # The default undesirable operators are `:::`, `<<-` and `->>`, we can modify this list
  # in the same way that we could modify the linters: using `with_defaults`
  undesirable_operator_linter = undesirable_operator_linter(
    # allow assignment to the parent env (`<<-`) but disallow right-assignment (`->`)
    with_defaults("<<-" = NULL, "->" = NA, default = default_undesirable_operators)
  ),
  #
  default = default_linters
  )
exclusions: list(
  # To prevent {lintr} from analysing specific files you can add an exclusions list to your .lintr config
  #
  # The exclusions is another named list. But you don't need to provide a name for each element,
  # if you want to exclude the whole of a file, just provide the filepath to that file:
  #
  # Ignore this file:
  "path/to/my_file.R",
  #
  # Ignore lines 1, 4, 6 and 7 from this file:
  "path/to/another/file" = c(1, 4, 6, 7)
  #
  # There is another way to exclude parts of files:
  # - using `# nolint` in a source file to ignore all subsequent code
  # - or wrapping a code block with `# nolint start` and `# nolint end`
  #
  # The code-level lint-exclusion flags can be user specified as well
  )

Some information on how to specify a .lintr config file. Eventually I'd rather write this up as a vignette for {lintr}. But hopefully this should explain the principles / syntax for any interested parties.

Arg! it isn't a legal .dcf, there doesn't appear to be a way to read.dcf and strip comments in R, so just treat it as illustrative. To make a usable .lintr config, strip all "#"-prefixed lines

For some reason you can't have a line containing a single close round bracket ). You must put a space before it: ).

Please note that for lintr v3 onwards, this config is not appropriate. You should use linters_with_defaults instead of with_defaults (and some of the named linters have probably changed names).
The closing round bracket thing is a .dcf format issue.

Please note that for lintr v3 onwards, this config is not appropriate. You should use linters_with_defaults instead of with_defaults (and some of the named linters have probably changed names).

Can we update the example?

The closing round bracket thing is a .dcf format issue.

I think it is a bug? Why it should not work if there is no space before?