r - Namespaces without packages

Question

In reorganising my code base I’d like to clean up my code sharing mechanism. So far I’m using source for lots of small, largely self-contained modules of functionality.

However, this approach suffers from a number of problems, among them

• the lack of tests for circularity (accidental circular source chains),
• complex syntax required to properly specify include paths (chdir=TRUE argument, hard-coded paths),
• potential of name clashes (when redefining objects).

Ideally I’d like to get something alike to the Python module mechanism. The R package mechanism would be overkill here:?I do not want to generate nested path hierarchies, multiple files with tons of metadata and manually build the package just to get a small, self-contained, reusable code module.

For now I’m using a code snippet which allows me to solve the first two problems mentioned above. The syntax for inclusion is like this:

import(functional)
import(io)
import(strings)

… and a module is defined as a simple source file which resides in the local path. The definition of import is straightforward but I cannot solve the third point: I want to import the module into a separate namespace but from what I see the namespace lookup mechanism is pretty hard-wired to packages. True, I could override `::` or getExportedValue and maybe asNamespace and isNamespace but that feels very dirty and has the potential of breaking other packages.

Answer 1

Here's a function that completely automates package creation, compilation, and reloading. As others have noted, the utility functions package.skeleton() and devtools::load_all() already get you almost all the way there. This just combines their functionality, using package.skeleton() to create the source directory in a temp directory that gets cleaned up when load_all() is done processing it.

All you need to do is point to the source files from which you want to read in functions, and give the package a name: import() does the rest for you.

import <- function(srcFiles, pkgName) {
    require(devtools)
    dd <- tempdir()
    on.exit(unlink(file.path(dd, pkgName), recursive=TRUE))
    package.skeleton(name=pkgName, path = dd, code_files=srcFiles)
    load_all(file.path(dd, pkgName))
}

## Create a couple of example source files
cat("bar <- function() {print('Hello World')}", file="bar.R")
cat("baz <- function() {print('Goodbye, cruel world.')}", file="baz.R")

## Try it out
import(srcFiles=c("bar.R", "baz.R"), pkgName="foo")

## Check that it worked
head(search())
# [1] ".GlobalEnv"        "package:foo"       "package:devtools"
# [4] "package:stats"     "package:graphics"  "package:grDevices"
bar()
# [1] "Hello World"
foo::baz()
# [1] "Goodbye, cruel world."