Pasting multi-line input eats comment

[lgoettgens]

We experience this in Oscar.jl (cf. oscar-system/Oscar.jl#4402 (comment))

Try pasting the full code block into the REPL:

julia> x = 1
       # hello
1

If you paste this in 1.11 it looks exactly like here, in 1.12-nightly (08d3c70) and nightly (f6e2b98) it changes to:

julia> x = 1
1

cc @benlorenz @c42f

[benlorenz]

It will also ignore all code following a comment (outside of arrays/tuples/blocks), pasting this

julia> x = 1
       #hello
       y = 2

will just print:

julia> x = 1
1

and y is not assigned.

For 1.11 and 1.10 it prints:

julia> x = 1
       #hello
1

But y is also ignored.

[KristofferC]

Bisected to 3e08cb1. Will see what commit in JuliaSyntax broke it.

[KristofferC]

JuliaSyntax commit that introduced this regression is in JuliaLang/JuliaSyntax.jl#493. cc @timholy

[mlechu]

@benlorenz I don't think we can change this without breakage. The REPL ignores output lines in this sort of paste (which I didn't know before looking into it), so anything not consumed by a Meta.parse starting at the prompt does not make the cut.

@KristofferC you're right that this issue is the same thing as #57345. I thought I could change the REPL behaviour independent of what Meta.parse does, but the ignored lines in a prompted paste are defined as "everything Meta.parse doesn't consume" and skipping over comments manually would be unwise.

Do you think we should revert JuliaLang/JuliaSyntax.jl#493 and restore the 1.10 and 1.11 behaviour? Given package test failures for either, I'm not sure what the compatible choice is.

[timholy]

I don't know either. CodeTracking transiently worked around this by disabling a test: timholy/CodeTracking.jl@f3a9f9b; that's not necessary after JuliaLang/JuliaSyntax.jl#493, but the current lack of a good substitute is not ideal. I'm not sure how serious the Documenter issues were, perhaps @mortenpi would know.