`World age increment not at top level` precompilation error with Julia 1.12+

[mortenpi]

Opening this mostly for visibility -- I think this is a PrecompileTools regression (JuliaLang/PrecompileTools.jl#58), but the syntax that causes it is a bit weird.

But HTTP fails to precompile on 1.12+ when using PrecompileTools 1.3.1 with:

Failed to precompile HTTP [cd3eb016-35fb-5094-929b-558a96fad6f3] to "/home/mortenpi/.julia/compiled/v1.12/HTTP/jl_evsPzI".
ERROR: LoadError: syntax: World age increment not at top level
Stacktrace:
  [1] top-level scope
    @ ~/oss/HTTP.jl/src/precompile.jl:3
  [2] include(mapexpr::Function, mod::Module, _path::String)
    @ Base ./Base.jl:304
  [3] top-level scope
    @ ~/oss/HTTP.jl/src/HTTP.jl:643
  [4] include(mod::Module, _path::String)
    @ Base ./Base.jl:303
  [5] include_package_for_output(pkg::Base.PkgId, input::String, depot_path::Vector{String}, dl_load_path::Vector{String}, load_path::Vector{String}, concrete_deps::Vector{Pair{Base.PkgId, UInt128}}, source::Nothing)
    @ Base ./loading.jl:3015
  [6] top-level scope
    @ stdin:5
  [7] eval(m::Module, e::Any)
    @ Core ./boot.jl:489
  [8] include_string(mapexpr::typeof(identity), mod::Module, code::String, filename::String)
    @ Base ./loading.jl:2861
  [9] include_string
    @ ./loading.jl:2871 [inlined]
 [10] exec_options(opts::Base.JLOptions)
    @ Base ./client.jl:326
 [11] _start()
    @ Base ./client.jl:560
in expression starting at /home/mortenpi/oss/HTTP.jl/src/precompile.jl:3
in expression starting at /home/mortenpi/oss/HTTP.jl/src/HTTP.jl:1
in expression starting at stdin:

It seems to be due to the withenv around @compile_workload (see the MWE in the linked issue):

HTTP.jl/src/precompile.jl

Lines 34 to 38 in 9db9aad

	withenv(env...) do
	@compile_workload begin
	HTTP.get(url);
	end
	end

[timholy]

The withenv will have to go inside the @compile_workload if you want high-quality precompilation. You can't put @compile_workload inside a thunk and expect Julia to defer compiling anything until after turning on compile-tracing.

[jpthiele]

The withenv will have to go inside the @compile_workload if you want high-quality precompilation. You can't put @compile_workload inside a thunk and expect Julia to defer compiling anything until after turning on compile-tracing.

I'm not familiar enough with the inner workings of precompilation.
Would this change fix the bug or is this mainly for optimizing precompilation?

Edit: it does fix the bug!

[timholy]

Both (it should fix the bug and improve your precompilation)

[IanButterworth]

Would it be possible for PrecompileTools to detect when it's being used in an already compiled thunk?

[bvdmitri]

Why hasn't it been caught by PkgEval ? HTTP.jl seems to be an essential part of Julia ecosystem?

[KristofferC]

Because it was introduced by a recent change in PrecompileTools.

[timholy]

Would it be possible for PrecompileTools to detect when it's being used in an already compiled thunk?

JuliaLang/PrecompileTools.jl#60 now uses Expr(Symbol("latestworld-if-toplevel")). I didn't know that existed until Keno pointed it out. It would make your JuliaLang/julia#58015 far simpler, you could just put it straight in the macro.