Resolve transcode method ambiguity

[bauglir]

The examples in many of the codec packages rely on being able to call transcode providing a Codec type and a string¹². #136 removed type annotations from the trailing arguments for transcode(::Type{C}, ...) where {C<:Codec} causing a method ambiguity with transcode(T, src::String) in Julia Base³. This adds an additional method to Base.transcode to resolve this ambiguity.

I have added tests for the Noop codec to ensure the ambiguity is resolved. I'm wondering whether it makes sense to add a test helper function that downstream packages can use to ensure this functionality remains intact. Let me know if that is something I should add.

Fixes #139.

Footnotes

1. https://github.com/JuliaIO/CodecZlib.jl/tree/f9fddaa28c093c590a7a93358709df2945306bc7#usage ↩

2. https://github.com/JuliaIO/CodecZstd.jl/tree/6327ffa9a3a12fc46d465dcfc8b30bed91cf284b#usage ↩

3. https://github.com/JuliaLang/julia/blob/ff7b8eb00bf887f20bf57fb7e53be0070a242c07/base/c.jl#L306 ↩

[bauglir]

In hindsight, using invoke to resolve the ambiguity seems like the more robust option long-term to ensure the implementation stays in sync.

[bauglir]

Any chance this can be merged and released @mkitti?

[mkitti]

I would like to go further with this.

We should run Test.detect_ambiguities() and make sure this is empty. Could you add that test?

[mkitti]

julia> using Test

julia> using TranscodingStreams

julia> detect_ambiguities(TranscodingStreams)
1-element Vector{Tuple{Method, Method}}:
 (transcode(::Type{C}, args...) where C<:TranscodingStreams.Codec in TranscodingStreams at /root/.julia/packages/TranscodingStreams/5yQuA/src/transcode.jl:33, transcode(T, src::String) in Base at c.jl:306)

[mkitti]

Add this somewhere in the tests please.

@test isempty(detect_ambiguities(TranscodingStreams))

[bauglir]

Could you add that test?

Yeah sure! I should be able to add that later today. I had held off on that because that also seems to be the point of #142.

[mkitti]

Let's just merge that then.

[bauglir]

Thanks for getting this merged. Any chance we can get a new release so downstream users do not have to work around this on v0.9.12?