[R-pkg-devel] active bindings in package namespace

[Jack Wasey]

Thanks for that thought. I do also do this in that package, and the same problem exists, since the code in those particular steps of R CMD check also calls .onLoad. These steps might even attach the package: the R CMD check code in tools is too convoluted for me to unravel, but the result is the same: active bindings defined directly in the namespace, or inserted into it from .onLoad, get run. .onAttach isn't possible because the namespace is sealed already.

In the example you offer from CLI, the binding is inserted into the "dummy" function's immediately enclosing environment, which is AFAIK not the same as the package namespace.

Jack

On 3/23/19 2:14 PM, Gábor Csárdi wrote:
> Hi, yet another workaround is to create the active binding in the
> .onLoad() function. Here is an example from the cli package:
> https://github.com/r-lib/cli/blob/d4756c483f69c2382c27b0b983d0ce7cc7e63763/R/onload.R#L8
> 
> Gabor
> 
> On Sat, Mar 23, 2019 at 3:50 PM Jack O. Wasey <jack using jackwasey.com> 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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