CODEWITHSUNDEEP
julia
Yly
Yly

Reputation: 2310

Making Julia find files in the LOAD_PATH

I want to help Julia find my .jl file by modifying the LOAD_PATH variable:

julia> readdir()
1-element Array{String,1}:
 "test.jl"

shell> cmd /c type test.jl
# Test.jl
module Test
export f
f() = println("hi")
end

julia> push!(LOAD_PATH,pwd());

julia> import Test
ERROR: ArgumentError: Module Test not found in current path.
Run `Pkg.add("Test")` to install the Test package.
 in require(::Symbol) at .\loading.jl:365

The first call to readdir() proves that I have a file called test.jl in my current directory. The following shell call shows that this file contains a module called Test. The next call to push!(LOAD_PATH,pwd()); puts the current directory in LOAD_PATH. But even with the current directory in LOAD_PATH, Julia still can't find the Test module in test.jl.

What's wrong?

Upvotes: 4

Views: 5241

Answers (1)

Gnimuc
Gnimuc

Reputation: 8566

The error was talking about something concerning require. As the doc says:

Given the statement using Foo, the system looks for Foo within Main. If the module does not exist, the system attempts to require("Foo"), which typically results in loading code from an installed package. ... require is case-sensitive on all platforms, including those with case-insensitive filesystems like macOS and Windows.

and the reason is clear: require couldn't find a file named Test in LOAD_PATH. So we need to make the file name matching the module name, but this is just a convention, not a mandatory rule. What will happen if someone mistakenly runs using test?

julia> push!(LOAD_PATH,pwd())
julia> using test
WARNING: requiring "test" in module "Main" did not define a corresponding module.
julia> whos()
                          Base  34427 KB     Module
                          Core  12386 KB     Module
                          Main  41296 KB     Module
                          Test   1837 bytes  Module

The result shows that we've loaded the file test.jl and the module(Test) in it, but not actually using/import the module. This is a respected behavior since we used a wrong module name, which is also the reason why julia complained in the warning. In this case, using test is equivalent to include("test.jl"), but I highly recommend you to follow the convention and do not use this behavior.

BTW, require became generally case-sensitive after this PR. A side-effect is your LOAD_PATH should also be case-sensitive, this will be fixed by this PR in julia-0.6.

Upvotes: 5

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