[RFC] don't load Pkg automatically

[fredrikekre]

In fbc30cd automatic loading of Pkg was added in interactive use. I propose to revert this for the following reasons:

• For interactive use most people should use the Pkg REPL, which will work regardless of this.
• It is a bit weird to load things automatically based on the mode; it makes interactive and non-interactive scripts behave differently.
• You can't load another package called Pkg.

[fredrikekre]

Also, people that really want Pkg available in the REPL without having to using Pkg can put that in startup.jl.

[vtjnash]

For interactive use most people should use the Pkg REPL, which will work regardless of this.

We shouldn’t need to embed a second programming language just to install packages

It is a bit weird to load things automatically based on the mode; it makes interactive and non-interactive scripts behave differently.

In the future, I think we expect to do much more of this. Pkg and InteractiveTools are simply the demo cases right now.

[KristofferC]

Please don't make irrelevant gripes about the lack of API documentation of Pkg in others PR. There is a Julia API and it is being documented right now. This PR has nothing to do with that.

[fredrikekre]

For interactive use most people should use the Pkg REPL, which will work regardless of this.

We shouldn’t need to embed a second programming language just to install packages

That seems completely unrelated to this PR. If you want to use Pkg just using Pkg just like you do with any other library. If that annoys you, put it in startup.jl.

In the future, I think we expect to do much more of this. Pkg and InteractiveTools are simply the demo cases right now.

Perhaps, but it should not be implemented like this, it has to be configurable. Otherwise the language makes it impossible to load other packages with the same name.

[vtjnash]

For interactive use most people should use the Pkg REPL, which will work regardless of this.

This isn't necessarily true or desirable. We're planning to remove Pkg from the system image as soon as we can without significantly impacting performance. The using Pkg call will thus be necessary for the REPL mode to be available. I thought we had an issue about this to link to (#5155 perhaps), but maybe it's been all in Slack discussion channels?

[KristofferC]

This isn't necessarily true or desirable. We're planning to remove Pkg from the system image as soon as we can without significantly impacting performance. The using Pkg call will thus be necessary for the REPL mode to be available.

So even more reason to do this then?

[StefanKarpinski]

The using Pkg call will thus be necessary for the REPL mode to be available.

Why? Activating the REPL mode can automatically load Pkg. All the more reason to prefer the REPL mode.

[KristofferC]

Will merge this in a while unless someone objects since otherwise it is impossible to load another package called Pkg (for example when developing it).

[vtjnash]

otherwise it is impossible to load another package called Pkg

The new code has made this annoyingly long to type, but let's not get carried away with calling it impossible. Specifically, it should be: const Pkg = (Base._require(Base.PkgId("Pkg")); Base.root_module(Base.PkgId("Pkg")))