RelocatableFolders.jl

An alternative to the @__DIR__ macro. Packages that wish to reference paths in their project directory run into issues with relocatability when used in conjunction with PackageCompiler. The @path macro provided by this package overcomes this limitation. See here and here for further details.

Usage

The package provides one export, the @path macro. It can be used to replace @__DIR__ in the following way:

module MyPackage

using RelocatableFolders

# const ASSETS = joinpath(@__DIR__, "../assets")
const ASSETS = @path joinpath(@__DIR__, "../assets")

end

At runtime the path stored in ASSETS will get resolved to either the original path, if it still exists, or to an automatically generated scratchspace containing the same folder and file structure as the original.

Limitations

This macro should only be used for reasonably small file or folder sizes. If there are very large files then it is better to make use of Julia's Artifact system instead.

Building new paths from, for example, ASSETS in the above example will return a String containing the resolved path rather than a Path object. Doing this at the module-level will result in hardcoded paths that will run into relocatability issues as discussed above. Always create a new @path for each resource you wish to reference rather than building them in parts, e.g.

module MyPackage

using RelocatableFolders

const ASSETS = @path joinpath(@__DIR__, "../assets")
const SUBDIR = @path joinpath(ASSETS, "subdir")
const FILE = @path joinpath(ASSETS, "file.txt")

end

Internals

At compile-time the @path macro will read in all the files contained in the referenced path and store them and their paths. The returned object is a Path <: AbstractString. Whenever a Path is passed to a function expecting an AbstractString (such as readdir) it will be converted to a String by looking up the stored path and returning that. When no path exists (the source tree no longer exists) then the contents of the files that were read at compile-time are written to a Scratch scratchspace and that path is returned instead.

Alternatives

The alternative approach is to use the Artifacts system to distribute the required files, which is a reasonably heavyweight solution for a simple collection of source-controlled files. It is recommended that users look to use artifacts when that file sizes are reasonably large and only use this package when the distributed files are small.