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Add read/write specialisation for IOContext{AnnIO} #53715

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May 2, 2024
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Add read/write specialisation for IOContext{AnnIO} #53715

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18 changes: 18 additions & 0 deletions base/strings/annotated.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -500,6 +500,24 @@ function write(dest::AnnotatedIOBuffer, src::AnnotatedIOBuffer)
nb
end

# So that read/writes with `IOContext` (and any similar `AbstractPipe` wrappers)
# work as expected.
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Still trying to wrap my brain around this:

  • by default, unsafe_write(io::AbstractPipe, ...) for simply redispatches to unsafe_write(pipe_writer(io)::IO, ...)
  • by default, all write(io, ...) methods in the end go through unsafe_write(io, ...)
  • so naively write(pipe_writer(io), s) seems pointless
  • but then there are custom write methods ... such as your write(io::AnnotatedIOBuffer, astr::Union{AnnotatedString, SubString{<:AnnotatedString}}) method...

And now we have a problem if AbstractPipe type, such as IOContext, wraps an AnnotatedIOBuffer: instead of dispatching from write(io, ...) to unsafe_write(io, ...) you need it to go through pipe_writer(io) so that the annotations can be handled by that.

What if there is a sandwich of three AbstractPipe types, say an IOContext outermost, then some other AbstractPipe type, then the AnnotatedIOBuffer -- it wouldn't work out then either, right?

This then makes me wonder: why not "simply" something like

write(io::AbstractPipe, s::AnnotatedString) = write(pipe_writer(io), s)

I bet you considered this and ruled it out for some reason, but I didn't see it in the PR discussion.

None of this is meant as fundamental objection to this PR, but I feel at least this comment should be a bit more elaborate (which, if you happen to agree with this POV, could certainly wait for a future PR -- I don't mind to hold this one up). I'd love to be helpful and suggest something, but for that I'd first have to really understand it, hence my questions :-).

function write(io::AbstractPipe, s::Union{AnnotatedString, SubString{<:AnnotatedString}})
if pipe_writer(io) isa AnnotatedIOBuffer
write(pipe_writer(io), s)
else
invoke(write, Tuple{IO, typeof(s)}, io, s)
end::Int
end
# Can't be part of the `Union` above because it introduces method ambiguities
function write(io::AbstractPipe, c::AnnotatedChar)
if pipe_writer(io) isa AnnotatedIOBuffer
write(pipe_writer(io), c)
else
invoke(write, Tuple{IO, typeof(c)}, io, c)
end::Int
end
Comment on lines +505 to +519
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The following is a 100% optional suggestion that is ultimately a matter of taste

As you are most likely aware, you could avoid the code duplication by using @eval, i.e.

Suggested change
function write(io::AbstractPipe, s::Union{AnnotatedString, SubString{<:AnnotatedString}})
if pipe_writer(io) isa AnnotatedIOBuffer
write(pipe_writer(io), s)
else
invoke(write, Tuple{IO, typeof(s)}, io, s)
end::Int
end
# Can't be part of the `Union` above because it introduces method ambiguities
function write(io::AbstractPipe, c::AnnotatedChar)
if pipe_writer(io) isa AnnotatedIOBuffer
write(pipe_writer(io), c)
else
invoke(write, Tuple{IO, typeof(c)}, io, c)
end::Int
end
# (can't do this via a single method with a 'Union' argument due to method ambiguities)
for T in (AnnotatedChar, AnnotatedString, SubString{<:AnnotatedString}) do
@eval function write(io::AbstractPipe, arg::$T)
if pipe_writer(io) isa AnnotatedIOBuffer
write(pipe_writer(io), arg)
else
invoke(write, Tuple{IO, typeof(arg)}, io, arg)
end::Int
end
end


"""
_clear_annotations_in_region!(annotations::Vector{Tuple{UnitRange{Int}, Pair{Symbol, Any}}}, span::UnitRange{Int})

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7 changes: 7 additions & 0 deletions test/strings/annotated.jl
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Expand Up @@ -209,4 +209,11 @@ end
@test write(aio2, Base.AnnotatedChar('c', [:b => 2, :c => 3, :d => 4])) == 1
@test Base.annotations(aio2) == [(1:2, :a => 1), (1:3, :b => 2), (3:3, :c => 3), (3:3, :d => 4)]
end
# Working through an IOContext
aio = Base.AnnotatedIOBuffer()
wrapio = IOContext(aio)
@test write(wrapio, Base.AnnotatedString("hey", [(1:3, :x => 1)])) == 3
@test write(wrapio, Base.AnnotatedChar('a', [:y => 2])) == 1
@test read(seekstart(aio), Base.AnnotatedString) ==
Base.AnnotatedString("heya", [(1:3, :x => 1), (4:4, :y => 2)])
end