lifecycle

# R Package Lifecycle Management

Manage function and argument lifecycle using tidyverse conventions and the lifecycle package.

## Setup

Check if lifecycle is configured by looking for `lifecycle-*.svg` files in `man/figures/`.

If not configured, run:

```r
usethis::use_lifecycle()
```

This:

- Adds lifecycle to `Imports` in DESCRIPTION
- Adds `@importFrom lifecycle deprecated` to the package documentation file
- Copies badge SVGs to `man/figures/`

## Lifecycle Badges

Insert badges in roxygen2 documentation:

```r
#' @description
#' `r lifecycle::badge("experimental")`
#' `r lifecycle::badge("deprecated")`
#' `r lifecycle::badge("superseded")`
```

For arguments:

```r
#' @param old_arg `r lifecycle::badge("deprecated")` Use `new_arg` instead.
```

Only badge functions/arguments whose stage differs from the package's overall stage.

## Deprecating a Function

1. Add badge and explanation to `@description`:

```r
#' Do something
#'
#' @description
#' `r lifecycle::badge("deprecated")`
#'
#' `old_fun()` was deprecated in mypkg 1.0.0. Use [new_fun()] instead.
#' @keywords internal
```

2. Add `deprecate_warn()` as first line of function body:

```r
old_fun <- function(x) {

lifecycle::deprecate_warn("1.0.0", "old_fun()", "new_fun()")
new_fun(x)
}
```

3. Show migration in examples:

```r
#' @examples
#' old_fun(x)
#' # ->
#' new_fun(x)
```

## Deprecation Functions

| Function           | When to Use                                             |
| ------------------ | ------------------------------------------------------- |
| `deprecate_soft()` | First stage; warns only direct users and during tests   |
| `deprecate_warn()` | Standard deprecation; warns once per 8 hours            |
| `deprecate_stop()` | Final stage before removal; errors with helpful message |

**Deprecation workflow for major releases:**

1. Search `deprecate_stop()` - consider removing function entirely
2. Replace `deprecate_warn()` with `deprecate_stop()`
3. Replace `deprecate_soft()` with `deprecate_warn()`

## Renaming a Function

Move implementation to new name, call from old name with deprecation:

```r
#' @description
#' `r lifecycle::badge("deprecated")`
#'
#' `add_two()` was renamed to `number_add()` for API consistency.
#' @keywords internal
#' @export
add_two <- function(x, y) {
lifecycle::deprecate_warn("1.0.0", "add_two()", "number_add()")
number_add(x, y)
}

#' Add two numbers
#' @export
number_add <- function(x, y) {
x + y
}
```

## Deprecating an Argument

Use `deprecated()` as default value with `is_present()` check:

```r
#' @param path `r lifecycle::badge("deprecated")` Use `file` instead.
write_file <- function(x, file, path = deprecated()) {
  if (lifecycle::is_present(path)) {
    lifecycle::deprecate_warn("1.4.0", "write_file(path)", "write_file(file)")
    file <- path
  }
  # ... rest of function
}
```

## Renaming an Argument

```r
add_two <- function(x, y, na_rm = TRUE, na.rm = deprecated()) {
  if (lifecycle::is_present(na.rm)) {
    lifecycle::deprecate_warn("1.0.0", "add_two(na.rm)", "add_two(na_rm)")
    na_rm <- na.rm
  }
  sum(x, y, na.rm = na_rm)
}
```

## Superseding a Function

For functions with better alternatives that shouldn't be removed:

```r
#' Gather columns into key-value pairs
#'
#' @description
#' `r lifecycle::badge("superseded")`
#'
#' Development on `gather()` is complete. For new code, use [pivot_longer()].
#'
#' `df %>% gather("key", "value", x, y, z)` is equivalent to
#' `df %>% pivot_longer(c(x, y, z), names_to = "key", values_to = "value")`.
```

No warning needed - just document the preferred alternative.

## Marking as Experimental

```r
#' @description
#' `r lifecycle::badge("experimental")`
cool_function <- function() {
  lifecycle::signal_stage("experimental", "cool_function()")
  # ...
}
```

## Testing Deprecations

Test that deprecated functions work and warn appropriately:

```r
test_that("old_fun is deprecated", {
  expect_snapshot({
    x <- old_fun(1)
    expect_equal(x, expected_value)
  })
})
```

Suppress warnings in existing tests:

```r
test_that("old_fun returns correct value", {
  withr::local_options(lifecycle_verbosity = "quiet")
  expect_equal(old_fun(1), expected_value)
})
```

## Deprecation Helpers

For deprecations affecting many functions (e.g., removing a common argument), create an internal helper:

```r
warn_for_verbose <- function(
  verbose = TRUE,
  env = rlang::caller_env(),
  user_env = rlang::caller_env(2)
) {
  if (!lifecycle::is_present(verbose) || isTRUE(verbose)) {
    return(invisible())
  }

  lifecycle::deprecate_warn(
    when = "2.0.0",
    what = I("The `verbose` argument"),
    details = c(
      "Set `options(mypkg_quiet = TRUE)` to suppress messages.",
      "The `verbose` argument will be removed in a future release."
    ),
    user_env = user_env
  )

  invisible()
}
```

Then use in affected functions:

```r
my_function <- function(..., verbose = deprecated()) {
  warn_for_verbose(verbose)
  # ...
}
```

## Custom Deprecation Messages

For non-standard deprecations, use `I()` to wrap custom text:

```r
lifecycle::deprecate_warn(
  when = "1.0.0",
  what = I('Setting option "pkg.opt" to "foo"'),
  with = I('"pkg.new_opt"')
)
```

The `what` fragment must work with "was deprecated in..." appended.

## Reference

See `references/lifecycle-stages.md` for detailed stage definitions and transitions.