Fix Base.isinteractive() for startup files

[petvana]

This PR aims to fix #10779 by deciding whether the session is interactive before the startup file is executed. PR also enables hot-fix to set interactivity for PyPlot in the startup file when using PackageCompiler, see #42425.

$cat ~/.julia/config/startup.jl
@show Base.isinteractive()

Before PR:

$ julia -q
Base.isinteractive() = false

After this PR:

$ julia -q
Base.isinteractive() = true

[KristofferC]

PR also enables hot-fix to set interactivity for PyPlot in the startup file when using PackageCompiler

Could you explain this a bit more?

[petvana]

@KristofferC You can add something like this to the startup file:

shell> cat ~/.julia/config/startup.jl
try PyPlot.plt.interactive(Base.isinteractive()) catch ; end

System image is build using

using PackageCompiler
create_sysimage([:PyPlot]; sysimage_path="sys_PyPlot.so")

... and the PyPlot works as expected

$ ./julia -J sys_PyPlot.so -q
julia> using PyPlot

julia> plt.isinteractive()
true

Alternative would be to use atreplinit().

Xref: JuliaPy/PyPlot.jl#476

[JeffBezanson]

Looks like this could be moved higher as well?

[petvana]

repl is only a local variable and seems not to have any effect before because it is always used as repl || is_interactive::Bool. So I moved it to the following if statement to simplify the code slightly.

[JeffBezanson]

Thanks, looks good to me.