Tool to tell if a package has unused dependencies or using unused packages

General Usage
1

When developing large projects, I sometimes 1) lose track of what packages I ]added but am not using any longer, and 2) what packages I’m using but not actually making use of.

Is there a tool to detect these kind of situations? Or how do you deal with that? Right now I’m just manually looking in the code to see what I need and what I don’t and I try (with Revise) to see if things fail when I remove stuff.

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2

First case (check packages that project Proj is actually using) should be easy:

using Proj
using TOML
deps = TOML.parsefile("Project.toml")["deps"]
for d in deps
    if !isdefined(Proj, Symbol(d))
    println("$d is not being used")
end

This is assuming the simple case in which Proj is only a module with the same name. Otherwise, you should navigate through the different modules of the project.

For the second case (check packages that are used/imported, but not really “used”), I have no idea.

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3

That should do it, although it should be possible to accomplish purely syntactically. If import X or using X doesn’t appear anywhere in the package code then X is not used. Parsing fully correctly is hard, of course, but Julia’s own parser and CSTParser both do it already.

4

We should add that to the VS Code linter.

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5

Thanks all, I’ll use that for the first part and wait for some linter magic for the second.

6

Start removing packages one by one, run all of your code and see when things break :laughing:

But seriously, thank you for asking this. I’m currently in a similar position, and have been trying to figure this out (the above method could take up to 16 hours per test, and I’ve got 6 or 7 packages I’m not sure of…)

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7

Would the linter address the second issue (using X but nothing from X is ever called)?

If not, is there currently a way of addressing this?

Thank you.

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8

I don’t think a linter should warn about the latter, because you might only have that call there to run the init function in the package, or the package might add a method to a function say in Base. In both cases that using statement does something, even though it might appear unnecessary.

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9

Well, it cold warn about it, and let the user choose. I’d wager that in most cases it’s just a unintended using…

10

Just tried this now, had to fix a few things, hopefully this helps:

using Proj
using Pkg.TOML
deps = TOML.parsefile("Project.toml")["deps"]
remove = String[]
for d in keys(deps)
    if !isdefined(Proj, Symbol(d))
        push!(remove, d)
    end
end
println("rm ", join(remove, " "))
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11

Sorry to resurrect this old topic but I noted a corner case:

Imagine that in MyPkg.jl I do a

using Printf: @printf

then

julia> isdefined(MyPkg,:Printf)
false

and the remove would incorrectly (at least to me) suggest to remove Printf. Any way to programmatically check for unused deps?

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12

FYI, I added the check for unused dependencies in Aqua.jl (Auto QUality Assurance for Julia packages). Either Aqua.test_all(YourPackage; stale_deps = true) or Aqua.test_stale_deps(YourPackage) should work.

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