[R-pkg-devel] Puzzled about "locked environments".

[Martin Morgan]

On 07/08/2018 07:23 PM, Duncan Murdoch wrote:
> On 08/07/2018 6:57 PM, Rolf Turner wrote:
>>
>> Recently I experimented with assigning a variable within the environment
>> of a function in a package that I am developing.  Slightly more 
>> explicitly:
>>
>> In a function "foo()" in the package, I have lines like:
>>
>>      big <- 42
>>      assign("big",big,envir=environment(bar))
>>
>> where "bar()" is another function in the package.
>>
>> This causes an error to be thrown:
>>
>>> Error in assign("big", big, envir = environment(bar)) :
>>>    cannot add bindings to a locked environment
>>
>> The reason that I am puzzled about this is that I used this syntax
>> repeatedly in my CRAN package "AssetPricing".  In this latter package
>> the syntax seems to work flawlessly.  No errors are thrown.  No mention
>> of "locked environments".
>>
>> Why would environments get "locked" in the package that I am currently
>> fooling about with, but not in the AssetPricing package?  Is there
>> anything that I  can do to keep environments from getting "locked"?
> 
> It may be the timing.  When R is installing a package, it executes all 
> of the code in the .R files (which has been consolidated into one file, 
> but that doesn't matter).  This produces all of the objects and 
> functions in the package.
> 
> Then it locks the environment, so that things don't change.
> 
> Then it compiles the functions.  If they were allowed to change, then 
> the compilation would have to be redone.
> 
> So perhaps AssetPricing makes the change in the .R file, processed 
> before locking, and your new package does it in a function, executed by 
> the user after locking.

AssetPricing does, at least some of the time, in the body of a function 
(the indentation is confusing)

environment(vupdate) <- new.env()
environment(scrG) <- new.env()
environment(initx) <- new.env()
environment(cev) <- new.env()

#
     assign("dS",dS,envir=environment(vupdate))
     assign("dS",dS,envir=environment(scrG))
     assign("dS",dS,envir=environment(initx))
     assign("dS",dS,envir=environment(cev))

so that assignment is to the unlocked new.env(). Presumably the new code 
assigns to bar's original environment, which is the (locked, once the 
package is loaded) package name space.

Martin Morgan

> 
> Or maybe not.
> 
> Duncan Murdoch
> 
>>
>> Can anyone suggest where I should start looking for differences in the
>> nature of the two packages?
>>
>> I could possibly give more detail, but I have no idea as to what might
>> be relevant.
>>
>> One difference is that AssetPricing involves no dynamically loaded
>> Fortran code, whereas the package that I am currently fooling about with
>> *does* involve such code.  (But neither "foo()" not "bar()" make direct
>> calls to .Fortran().)
>>
>> Grateful for any insights.
>>
>> cheers,
>>
>> Rolf Turner
>>
> 
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