Evaluate imports first, other code second

[VarLad]

MWE:

import Pkg, Malt
p = Malt.Worker()
j = Pkg.PackageSpec(name="Malt")

Malt.remote_eval_fetch(p, quote
    import Pkg;
    @info $j
end)

ERROR: Remote exception from Malt.Worker on port 9219 with PID 416219:

KeyError: key Base.PkgId(Base.UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Pkg") not found
Stacktrace:

This works perfectly in Julia 1.10.2
@savq Any idea what might be wrong here? I could also reproduce this with Distributed as well but for some reason the MWE with Distributed is working.

[VarLad]

There was some discussion on Slack on how to fix this!
It can be found at:
https://julialang.slack.com/archives/C67910KEH/p1714389271264479

Some important headers:
An acceptable reason for this happening was given:

I think the reason this used to work was because Pkg was in the sysimage (which it is not on 1.11). Just using some other package:

import Example, Malt
p = Malt.Worker()
j = Example.domath

Malt.remote_eval_fetch(p, quote
    import Example
    $j
end)

gives the same error.

Distributed.jl has code where it looks up all the imports in a code block, executes that first, and then runs the code: https://github.com/JuliaLang/Distributed.jl/blob/3b889eecfdccb7febb9ae8abf9e3c604ffbc40ea/src/macros.jl#L197-L206 Perhaps Malt could do something like that as well?

[fonsp]

Thanks for the bug report and the helpful links! Could you save a copy of the slack conversation on github gist and share the link?

[VarLad]

@fonsp Apologies for the late reply
Is this good enough or should I format better?

[fonsp]

Another good option is to improve the error message: for example:

1. if there is a serialization error while sending the expression
2. if it's a KeyError with Base.PkgId as key type
3. then write "The expression to evaluate contains objects from package $x, but this package has not yet been imported on the worker."
4. if the original expression contains import $x, then write "Try to first evaluate and wait for import $x, and then evaluate the rest of the expression."