assignment_linter with "%<>%" operator causes sprintf error

[arun-ramamurthy]

I want to configure my .lintr file to allow for the %<>% operator.

However, using assignment_linter with argument operator containing %<>% is causing strange lintr errors with unrelated lines in my .R files - specifically, it appears to be related to function default arguments as in a = "test" below.

Please see this reprex and the associated error below:

library(lintr)

lines <- c(
  'f <- function(',
  '  a = "test"',
  ') {',
  '}'
)

lint(
  text = lines,
  linters = assignment_linter(operator = c("<-"))
)
#> ℹ No lints found.

lint(
  text = lines,
  linters = assignment_linter(operator = c("%<>%"))
)
#> Error in `lint()`:
#> ! Linter `linter()` failed in '/tmp/RtmpI5xsy4/fileba94779980551':
#> Caused by error in `sprintf()`:
#> ! invalid format '%<>% f'; use format %s for character objects

^{Created on 2025-04-22 with reprex v2.1.1}

[arun-ramamurthy]

If at all helpful, here is the full trace:

> rlang::last_trace(drop=F)
<error/rlang_error>
Error in `lint()`:
! Linter `linter()` failed in /tmp/Rtmpw4a1aU/fileccc254f7412f8:
Caused by error in `sprintf()`:
! invalid format '%<>% f'; use format %s for character objects
---
Backtrace:
     ▆
  1. ├─lintr::lint(text = lines, linters = assignment_linter(operator = c("%<>%")))
  2. │ ├─base::withCallingHandlers(...) at lintr/R/lint.R:91:9
  3. │ └─lintr:::get_lints(...) at lintr/R/lint.R:91:9
  4. │   ├─lintr:::flatten_lints(linter_fun(expr)) at lintr/R/lint.R:318:5
  5. │   │ └─lintr:::flatten_list(x, class = "lint") at lintr/R/utils.R:18:3
  6. │   │   └─lintr (local) assign_item(x) at lintr/R/utils.R:36:3
  7. │   └─lintr (local) linter_fun(expr) at lintr/R/lint.R:318:5
  8. │     └─base::sprintf(op_lint_message_fmt, op_text) at lintr/R/assignment_linter.R:175:7
  9. └─base::.handleSimpleError(...)
 10.   └─lintr (local) h(simpleError(msg, call))
 11.     └─cli::cli_abort(...) at lintr/R/lint.R:94:13
 12.       └─rlang::abort(...) at cli/R/rlang.R:45:3