aDear list,
I'm aware of the fact that I posted on something related a while ago,
but I just can't sweat this off and would like to ask your for an opinion:
The problem:
Namespaces are great, but they don't resolve certain conflicts regarding
name clashes. There are more and more people out there trying to come up
with their own R packages, which is great also! Yet, it becomes more and
more likely that programmers will choose identical names for their
exported functions and/or that they add functionality to existing
function (i.e. overwriting existing functions).
The whole process of which packages overwrite which functions is
somewhat obscure and in addition depends on their order in the search
path. On the other hand, it is not possible to use "namespace"
functionality (i.e. 'namespace::fun()'; also less efficient than direct
call; see illustration below) during early stages of the development
process (i.e. the package is not finished yet) as there is no namespace
available yet.
I know of at least two cases where such overwrites (I think it's called
masking, right?) led to some confusion at our chair:
1) loading package forecast overwrites certain functions in stats which
made some code refactoring necessary
2) loading package 'R.utils' followed by package 'roxygen' overwrites
'parse.default()' which results in errors for something like
'eval(parse(text="a <- 1"))' ; see illustration below)
And I'm sure the community could come up with lots more of such scenarios.
Suggestions:
1) In order to avoid name clashes/unintended overwrites, how about
switching to a coding paradigm that explicitly (and automatically)
includes a package's name in all its functions' names once code is
turned into a real package? E.g., getting used to "preemptively" type
'package_fun()' or 'package.fun()' instead of just 'fun()'. Better to be
save than sorry, right? This could be realized pretty easily (see
example below) and, IMHO, would significantly increase transparency.
2) In order to avoid intended (but for the user often pretty obscure)
overwrites of existing functions, we could use the same mechanism
together with the "rule": just don't provide any functions that
overwrite existing ones, rather prepend your version of that function
with your package name and leave it up to the user which version he
wants to call.
At the moment, all of this is probably not that big of a deal yet, but
my suggestion has more of a mid-term/long-term character.
Below you find a little illustration. I'm probably asking too much, but
it'd be great if we could get a little discussion going on how to
improve the way of loading packages!
Best regards and thanks for R and all it's packages!
Janko
################################################################################
# PROOF OF CONCEPT
################################################################################
# 1) PROBLEM
# IMHO, with the number of packages submitted to CRAN constantly increasing,
# over time we will be likely to see problems with respect to name clashes.
# The main reasons I see for this are the following:
# a) package developers picking identical names for their exported functions
# b) package developers overwriting base functions in order to add
functionality
# to existing functions
# c) ...
#
# This can create scenarios in which the user might not exactly know that
# he/she is using a 'modified' version of a specific function. More so,
the user
# needs to carefully read the description of each new package he plans
# to use in order to find out which functions are exported and which
existing
# functions might be overwritten. This in turn might imply that the user's
# existing code needs to be refactored (i.e. instead of using 'fun()' it
# might now be necessary to type 'namespace::fun()' to be sure that the
desired
# function is called).
# 2) SUGGESTED SOLUTION
# That being said, why don't we switch to a 'preemptive' coding paradigm
# where the default way of calling functions includes the specification of
# its namespace? In principle, the functionality offered by
'namespace::fun()'
# gets the job done.
# BUT:
# a) it is slower compared to the direct way of calling a function.
# (see illustration below).
# b) this option is not available througout the development process of a
package
# as there is no namespace yet and there's no way to emulate one.
This in
# turn means that even though a package developer would buy into
strictly
# using 'mypkg::fun()' throughout his package code, he can only do so
at the
# very final stage of the process RIGHT before turning his code into a
# working package (when he's absolutely sure everything is working as
planned).
# For debugging he would need to go back to using 'fun()'. Pretty
cumbersome.
# So how about simply automatically prepending a given function's name with
# the package's name for each package that is build (e.g. 'pkg.fun()' or
# 'pkg_fun()')? In the end, this would just be a small change for new
packages
# without a significant decrease of performance and it could also be
realized
# at early stages of the development process (see illustration below).
# 3) ILLUSTRATION
# Example case where base function 'parse.default' is overwritten:
parse(text="a <- 5") # Works
require(R.utils)
require(roxygen)
parse(text="a <- 5") # Does not work anymore
################# START A NEW R SESSION BEFORE YOU CONTINUE
####################
# Inefficiency of 'namespace::fun()':
require(microbenchmark)
res.a <- microbenchmark(eval(parse(text="a <- 5")))
res.b <- microbenchmark(eval(base::parse(text="a <- 5")))
median(res.a$time)/median(res.b$time)
# Can be made up by explicit assignment:
foo <- base::parse
res.a <- microbenchmark(eval(parse(text="a <- 5")))
res.b <- microbenchmark(eval(foo(text="a <- 5")))
median(res.a$time)/median(res.b$time)
# Automatically prepend function names:
processNamespaces <- function(
do.global=FALSE,
do.verbose=FALSE,
.delim.name="_",
...
){
srch.list.0 <- search()
srch.list <- gsub("package:", "", srch.list.0)
if(!do.global){
assign(".NS", new.env(), envir=.GlobalEnv)
}
out <- lapply(1:length(srch.list), function(x.pkg){
pkg <- srch.list[x.pkg]
# SKIP LIST
if(pkg %in% c(".GlobalEnv", "Autoloads")){
return(NULL)
}
# /
# TARGET ENVIR
if(!do.global){
# ADD PACKAGE TO .NS ENVIRONMENT
envir <- eval(substitute(
assign(PKG, new.env(), envir=.NS),
list(PKG=pkg)
))
# /
# envir <- get(pkg, envir=.NS, inherits=FALSE)
envir.msg <- paste(".NS$", pkg, sep="")
} else {
envir <- .GlobalEnv
envir.msg <- ".GlobalEnv"
}
# /
# PROCESS FUNCTIONS
cnt <- ls(pos=x.pkg)
out <- unlist(sapply(cnt, function(x.cnt){
value <- get(x.cnt, pos=x.pkg, inherits=FALSE)
obj.mod <- paste(pkg, x.cnt, sep=.delim.name)
if(!is.function(value)){
return(NULL)
}
if(do.verbose){
cat(paste("Assigning '", obj.mod, "' to '", envir.msg,
"'", sep=""), sep="\n")
}
eval(substitute(
assign(OBJ.MOD, value, envir=ENVIR),
list(
OBJ.MOD=obj.mod,
ENVIR=envir
)
))
return(obj.mod)
}))
names(out) <- NULL
# /
return(out)
})
names(out) <- srch.list
return(out)
}
# +++++
funs <- processNamespaces(do.verbose=TRUE)
ls(.NS)
ls(.NS$base)
.NS$base$base_parse
res.a <- microbenchmark(eval(parse(text="a <- 5")))
res.b <- microbenchmark(eval(.NS$base$base_parse(text="a <- 5")))
median(res.a$time)/median(res.b$time)
#+++++
funs <- processNamespaces(do.global=TRUE, do.verbose=TRUE)
base_parse
res.a <- microbenchmark(eval(parse(text="a <- 5")))
res.b <- microbenchmark(eval(base_parse(text="a <- 5")))
median(res.a$time)/median(res.b$time)
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