Parser errors and using

[Keno]

Consider the following:

foo.jl

module Foo
using Bar
end

bar.jl

module Bar
.
end

julia> using Bar
ERROR: syntax: invalid identifier name .
 in include_from_node1 at loading.jl:91
 in reload_path at loading.jl:114
 in require at loading.jl:48
at /Users/keno/Documents/src/julia/Bar.jl:1

julia> using Bar
ERROR: syntax: invalid identifier name .
 in include_from_node1 at loading.jl:91
 in reload_path at loading.jl:114
 in require at loading.jl:48
at /Users/keno/Documents/src/julia/Bar.jl:1

julia> using Foo
ERROR: syntax: invalid identifier name .
 in include_from_node1 at loading.jl:91
 in reload_path at loading.jl:114
 in require at loading.jl:48
 in include_from_node1 at loading.jl:91
 in reload_path at loading.jl:114
 in require at loading.jl:48
at /Users/keno/Documents/src/julia/Bar.jl:1
at /Users/keno/Documents/src/julia/Foo.jl:2

julia> using Foo

julia>

We already try to do this but in cases like the Foo module above, we just get a partially evaluated foo module. Ideally this should fail in the same way the second time.

[JeffBezanson]

What should the following do:

module Foo
a = 1
error()
b = 2
end

?

[Keno]

probably not bind the module Foo. I find it really bad to have a partially evaluated module, but I'm not sure.

[JeffBezanson]

I agree that it is bad, but you might want to debug the error. I guess there is much to be said for doing as little as possible during module load time.

[Keno]

alight, how about this then. If you explicitly include something you get a partially evaluated module, but if you just say using Foo, you don't. Not sure how feasible that is.

[JeffBezanson]

It's probably feasible, but people also do using programmatically (via macros or eval), so it's hard to make a distinction between what results in throwing out the module and what doesn't. The module might also have added methods to functions in other modules. This is a reason to prefer a more static using; for example if all using statements had to occur before any other expressions then this would be easy to deal with.

I wish we had a better solution for conditional using; it's really only a load-time thing and won't work at init time or run time, so the usingmodule function is excessive.

[StefanKarpinski]

This seems non-breaking since it only affects behavior when code is broken anyway.

[Keno]

Between precompilation and Revise, this is not an issue any more in day-to-day work.