throw correct LoadError from compilecache

[stevengj]

Since Base.compilecache runs in a subprocess, any exception that is thrown is printed to stderr but is not rethrown in the parent process, which just throws an ErrorException.

This is annoying in the case of a module Foo that has a syntax error or something else that would ordinarily throw a LoadError on import. All of the nice formatting etcetera (e.g. coloring in the terminal, or special handling in IJulia/Jupyter) is lost and the LoadError gets printed as plain text, and then an ErrorException is thrown in addition.

Is there some way to serialize the LoadError and backtrace from the child process so that they get rethrown in the parent process?

[bermanmaxim]

I hit this same issue today, by trying to catch the absence of a file loaded using JLD:

using JLD
try
    a = load("test.jld", "w0")
catch y
    if isa(y, LoadError)
        a = rand(1000);
        save("test.jls", "a", a);
    else
        rethrow()
    end
end

LoadError: File test.jld cannot be found
while loading In[45], in expression starting on line 9

 in jldopen at /home/.julia/v0.4/JLD/src/JLD.jl:142
 in jldopen at /home/.julia/v0.4/JLD/src/JLD.jl:209
 in jldopen at /home/.julia/v0.4/JLD/src/JLD.jl:219
 in load at /home/.julia/v0.4/JLD/src/JLD.jl:1111

the catch sees y as a general ErrorException instead of a LoadError, despite this name being printed on screen.

[timholy]

LoadError changed quite drastically in #29901, #30900, and perhaps others. I suggest we close this as the test case is no longer reproducible and the OP doesn't contain a test case.