Yes, the rules for visibility of objects in the `data` directory are
somewhat strange, but they are documented in "Writing R Extensions",
section 1.1.6. They're also summarized here:
https://stackoverflow.com/a/79122709 .
In defence of the strange rules: you don't have to use them unless you
choose to do so. If you want "normal" visibility rules for data, just
create it using code in the R directory. Then your data will always be
visible to functions in your package, and if you export it in the
NAMESPACE file, always visible to users of your package using the same
rules as for exported functions.
Duncan Murdoch
On 2025-10-15 12:08 p.m., Spencer Graves wrote:
Thanks, Duncan.
This is the first package I've created trying to follow Wickham and
Bryan, R Packages, including using roxygen2. That DESCRIPTION file
includes "LazyData: true". I don't remember if I used
"usethis::use_data()", but I probably did.
I was surprised that I had to use "::" inside "tests/testthat/test-*.R"
to access a dataset defined in that package! And I seemed to get the
problem only on my local computer while all 5 standard GitHub Actions
seemed not to need that.
That's what led me to impose upon the time of the experts who contribute
to this email list.
Thanks again, Spencer Graves
On 10/15/25 09:52, Duncan Murdoch wrote:
On 2025-10-14 5:16 a.m., Chris Black wrote:
On Oct 14, 2025, at 1:38 AM, Georgi Boshnakov
<[email protected]> wrote:
So, you can't access them with the '::' operator, you need to use
data().
You can, though!
```
% R --vanilla -q -e 'datasets::AirPassengers'
datasets::AirPassengers
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1949 112 118 132 129 121 135 148 148 136 119 104 118
1950 115 126 141 135 125 149 170 170 158 133 114 140
1951 145 150 178 163 172 178 199 199 184 162 146 166
1952 171 180 193 181 183 218 230 242 209 191 172 194
1953 196 196 236 235 229 243 264 272 237 211 180 201
1954 204 188 235 227 234 264 302 293 259 229 203 229
1955 242 233 267 269 270 315 364 347 312 274 237 278
1956 284 277 317 313 318 374 413 405 355 306 271 306
1957 315 301 356 348 355 422 465 467 404 347 305 336
1958 340 318 362 348 363 435 491 505 404 359 310 337
1959 360 342 406 396 420 472 548 559 463 407 362 405
1960 417 391 419 461 472 535 622 606 508 461 390 432
```
This is also explicit in R Internals 1.17 ([1], emphasis added):
"Lazy-load databases are loaded into the exports for a package, but
not into the namespace environment itself. Thus they are visible when
the package is attached, ***and also via the :: operator.***”
[1] https://cran.r-project.org/doc/manuals/r-release/R-ints.html#Lazy-
loading
That's true provided the data is lazy-loaded. The default is "LazyData:
false", but "LazyData: true" is a pretty common choice because
usethis::use_data() puts that in DESCRIPTION.
Duncan Murdoch
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