Requires.jl

Requires is a Julia package that will magically make loading packages faster, maybe. It supports specifying glue code in packages which will load automatically when a another package is loaded, so that explicit dependencies (and long load times) can be avoided.

Usage is as simple as

media(::MyType) = Textual()

@require Gadfly begin
  media(::Gadfly.Plot) = Graphical()
end

For larger amounts of code you can also use @require Package include("glue.jl"). The code wrapped by @require will execute as soon as the given package is loaded (which may be immediately).

julia> using Requires

julia> @require DataFrames println("foo")

julia> using DataFrames
foo

julia> @require DataFrames println("bar")
bar

Note that the package is not imported by default – you need an explicit using statement if you want to use the packages names without qualifying them.

See here for some more detailed examples.

---

This package also provides the @lazymod macro, which provides a way to load modules the first time they are used.

julia> using Requires

julia> @lazymod DataFrames
dataframes (generic function with 1 method)

julia> dataframes().DataFrame # This will take a few seconds
DataFrame (constructor with 22 methods)

julia> dataframes().DataFrame # This will be instant
DataFrame (constructor with 22 methods)

If the module you want to load lazily lives in its own file within your package, you can also use

@lazymod MyMod "src/mymod.jl"

The source file will then be includeed when the module is first used. See here for an example.