Dear Jack
This doesn't answer your question, but I would advise against this design.
- Users do not expect side effects (such as network access) from
accessing a symbol.
- A function gives you much more flexibility to change the interface
later on. (Arguments for fetching the data, tokens for API access, ...)
- You already encountered a few quirks that make this an "interesting"
problem.
A function call only needs a pair of parentheses.
Best regards
Kirill
On 23.03.19 16:50, Jack O. Wasey wrote:
Dear all,
I am developing a package which is a front for various online data
(icd.data https://github.com/jackwasey/icd.data/ ). The current CRAN
version just has lazy-loaded data, but now the package encompasses far
more current and historic ICD codes from different countries, these
can't be included in the CRAN package even with maximal compression.
Other authors have solved this using functions to get the data, with
or without a local cache of the retrieved data. No CRAN or other
packages I have found after extensive searching use the attractive
active binding feature of R.
The goal is simple: for the user to refer to the data by its symbol,
e.g., 'icd10fr2019', or 'icd.data::icd10fr2019', and it will be
downloaded and parsed transparently (if the user has already granted
permission, or after prompt if they haven't).
The bindings are set using commands alongside the function definitions
in R/*.R .E.g.
makeActiveBinding("icd10cm_latest", .icd10cm_latest_binding,
environment())
lockBinding("icd10cm_latest", environment())
For non-interactive use, CI and CRAN tests, no data should be
downloaded, and no cache directory set up without user consent. For
interactive use, I ask permission to create a local data cache before
downloading data.
This works fine... until R CMD check. The following steps seems to
'get' or 'source' everything from the package namespace, which results
in triggering the active bindings, and this fails if I am unable to
get consent to download data, and want to 'stop' on this error condition.
- checking dependencies in R code
- checking S3 generic/method consistency
- checking foreign function calls
- checking R code for possible problems
Debugging CI-specific binding bugs is a nightmare because these occur
in different R sessions initiated by R CMD check.
There may be legitimate reasons to evaluate everything in the
namespace, but I've no idea what they are. Incidentally, Rstudio also
does 'mget' on the whole package namespace and triggers bindings
during autocomplete. https://github.com/rstudio/rstudio/issues/4414
Is this something I should raise as an issue with R? Or does anyone
have any idea of a sensible approach to this. Currently I have a set
of workarounds, but this complicates the code, and has taken an awful
lot of time. Does anyone know of any CRAN package which has active
bindings in the package namespace?
Any ideas appreciated.
Jack Wasey
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