How to make changes/develop a package in the StdLib?

Tooling Package Management
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Hello, I want to add function to Downloads.jl (to allow overriding the default Downloader). Downloads.jl is in the stdlib/default sysimage, and I am not sure what the best development flow is for making changes and testing. Do I need to build julia from scratch to make changes to Downloads.jl? I have tried using ] dev Downloads.jl in a clean environment using default sysimage and that does not seem to work. – adding a function a restarting julia has no effect.

Thank you, Nehal

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The quick way is to change the UUID temporarily, so that Julia sees it as a separate package from the baked-in version. See https://github.com/JuliaLang/Pkg.jl#using-the-development-version-of-pkgjl for how to do that (that’s for Pkg.jl, but it’s the same process for any stdlib pretty much).

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Thank you very much – instructions were easy to follow and was able to get it to work.

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