Fix show() error while calling UDPSocket() in REPL.

[abhijithanilkumar]

Calling UDPSocket() displays this now.

julia> UDPSocket()
UDPSocket(init)

Fixes #13711

[abhijithanilkumar]

@tkelman What tests should be implemented here?

[kshyatt]

@abhijithanilkumar tests for show can be seen here.

[abhijithanilkumar]

@kshyatt Is the displayed message fine? Or should it be changed to something else?

[tkelman]

This is good, though there's an underlying issue that the show method that was previously being called for the LibuvStream abstract type assumes the presence of a buffer field. That's apparently a bad assumption, question is whether there are counterexamples other than UDPSocket?

[abhijithanilkumar]

@tkelman TCPSocket and UDPSocket uses LibuvStream. TCPSocket works fine.

[kshyatt]

I think the message is fine. @tkelman I grepped for <: LibuvStream and every other subtype has a buffer member.

[tkelman]

I'm not sure whether that type is meant to be subtyped by packages. If not, maybe the existing show method should be made more specific to only apply to TCPSocket.

[kshyatt]

The existing show method also works for TTY AFAICT.

[tkelman]

Are there other methods on the abstract LibuvStream that make similar type member assumptions? show might not be the only thing broken.

[rohitvarkey]

@tkelman @abhijithanilkumar Seems like there are a few methods which are broken due to this assumption. Few examples. (This is on 0.4.1)

julia> nb_available(s)
ERROR: type UDPSocket has no field buffer
 in nb_available at stream.jl:254

julia> isreadable(s);
ERROR: type UDPSocket has no field buffer
 in isreadable at stream.jl:243

julia> isopen(s);
ERROR: type UDPSocket has no field buffer
 in print at strings/io.jl:8
 in print_to_string at strings/io.jl:36
 in isopen at stream.jl:317

[rohitvarkey]

I also found a duplicate method for nb_available.

julia/base/stream.jl

Line 87 in 0ea14f8

nb_available(s::LibuvStream) = nb_available(s.buffer)

julia/base/stream.jl

Line 253 in 0ea14f8

nb_available(stream::LibuvStream) = nb_available(stream.buffer)

[abhijithanilkumar]

@tkelman What has to be done here?

[tkelman]

needs to add tests of this method

[abhijithanilkumar]

@tkelman I'm a newbie to Julia. Where should I add the tests? 😅 @kshyatt I didn't really understand show tests you posted. I thought I was making a call to an already existing show method. Please correct me if I'm wrong.

[tkelman]

test/socket.jl would seem like a natural place

[abhijithanilkumar]

@tkelman Is this okay?

[tkelman]

I think that looks right. repr shouldn't result in any stdout output, I think.

[tkelman]

Once this is merged we should open a new issue for the other methods that don't work on UDPSocket for the same underlying reason that @rohitvarkey described above.

[abhijithanilkumar]

@tkelman So is the work here done? Anything else to be covered?