Literate.notebook & Plots: "_show is not defined for this backend. m=text/plain"

[mcabbott]

When generating a notebook which contains Plots.jl plot() commands, I get a warning _show is not defined for this backend. m=text/plain.

MWE: this file produces the error, attached as .txt to please github: test.jl.txt. Contents is:

# Save this as `test.jl` on the desktop, and then run
# ```
# using Literate
# Literate.notebook("/Users/me/Desktop/test.jl","/Users/me/Desktop/")
# ```
using Plots
gr()
plot(rand(20))

# That gives a warning, uncommenting these lines gives an error:

# unicodeplots()
# plot(rand(20))

Here is the warning produced:

julia> using Literate
julia> Literate.notebook("/Users/me/Desktop/test.jl","/Users/me/Desktop/")
Info: generating notebook from /Users/me/Desktop/test.jl
Info: not running on Travis, skipping links will not be correct.
Info: executing notebook test.ipynb
WARNING: _show is not defined for this backend. m=text/plain

If I uncomment the last two lines of the file, and run that again, then in addition I get the following errors:

┌────────────────────────────────────────────────────────────┐
0.9 │⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│ y1
│⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⠀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⢸⢣⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⢸⠀⢣⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡸⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⡜⠀⠀⢣⢀⡠⠔⡆⠀⠀⠀⢰⠁⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇⠀⠀⠀⠀⡇⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⡇⠀⠀⠀⠁⠀⠀⡇⠀⠀⠀⢸⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡜⢣⠀⠀⠀⢰⠁⠘⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⢆⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⢸⠀⠀⠀⡸⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠇⠸⡀⠀⠀⡸⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡸⠀⠑⢄⡀⠀⠀│
│⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠘⡄⠀⠀⡇⠀⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⠀⡇⠀⠀⡇⠀⠀⢱⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⢇⠀⠀│
│⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⡇⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡎⠀⠀⢸⠀⢠⠃⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢰⠁⠀⠀⠀⠘⡄⠀│
│⠀⠀⠀⠀⡜⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⢸⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⢸⢇⠀⠀⢠⠃⠀⠀⠈⡆⢸⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⢱⠀│
│⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠘⡄⢸⠀⠀⠀⠘⡄⠀⠀⠀⠀⠀⡜⠈⢆⠀⢸⠀⠀⠀⠀⢣⡇⠀⠀⠀⠀⢣⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⢇│
│⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⡎⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⡇⠀⠈⡆⡇⠀⠀⠀⠀⠸⠇⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠃⠀⠀⠀⠀⠀⠀⠘│
│⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇⠀⠀⠀⠀⡇⠀⠀⠀⠀⢰⠁⠀⠀⠘⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢇⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠇⠀⠀⠀⠀⢱⠀⠀⠀⠀⡸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢆⠀⠀⠀⡰⠢⣀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⡜⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢆⢀⠎⠀⠀⠀⠑⠇⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡀⠀⠀⢠⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠱⡀⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
│⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠱⡀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
0 │⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠱⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀│
└────────────────────────────────────────────────────────────┘
0                                                           20
WARNING: _show is not defined for this backend. m=image/svg+xml
WARNING: _show is not defined for this backend. m=application/pdf
Error: error when executing notebook based on input file: /Users/me/Desktop/test.jl
ERROR: FileIO.File{FileIO.DataFormat{:UNKNOWN}}("/var/folders/1b/6flsxnb12rx3r3ktpr_zllyc0000gn/T/juliaiokN4H.pdf") couldn't be recognized by FileIO.

Stacktrace:
[1] #load#20(::Array{Any,1}, ::Function, ::FileIO.File{FileIO.DataFormat{:UNKNOWN}}) at /Users/me/.julia/v0.6/FileIO/src/loadsave.jl:88
[2] load(::FileIO.File{FileIO.DataFormat{:UNKNOWN}}) at /Users/me/.julia/v0.6/FileIO/src/loadsave.jl:86
[3] #load#13(::Array{Any,1}, ::Function, ::String) at /Users/me/.julia/v0.6/FileIO/src/loadsave.jl:52
[4] _show(::IOContext{Base64EncodePipe}, ::MIME{Symbol("image/png")}, ::Plots.Plot{Plots.UnicodePlotsBackend}) at /Users/me/.julia/v0.6/Plots/src/output.jl:230
[5] show(::IOContext{Base64EncodePipe}, ::MIME{Symbol("image/png")}, ::Plots.Plot{Plots.UnicodePlotsBackend}) at /Users/me/.julia/v0.6/Plots/src/output.jl:210
[6] limitstringmime(::MIME{Symbol("image/png")}, ::Plots.Plot{Plots.UnicodePlotsBackend}) at /Users/me/.julia/v0.6/Literate/src/IJulia.jl:68
[7] display_dict(::Plots.Plot{Plots.UnicodePlotsBackend}) at /Users/me/.julia/v0.6/Literate/src/IJulia.jl:28
[8] execute_notebook(::Dict{Any,Any}) at /Users/me/.julia/v0.6/Literate/src/Literate.jl:532
[9] #15 at /Users/me/.julia/v0.6/Literate/src/Literate.jl:466 [inlined]
[10] cd(::Literate.##15#19, ::String) at ./file.jl:70
[11] #notebook#11(::Base.#identity, ::Base.#identity, ::Bool, ::Bool, ::Bool, ::String, ::Array{Any,1}, ::Function, ::String, ::String) at /Users/me/.julia/v0.6/Literate/src/Literate.jl:465
[12] notebook(::String, ::String) at /Users/me/.julia/v0.6/Literate/src/Literate.jl:396

[fredrikekre]

Thanks for the report. All errors here are actually thrown from within Plots.jl, so its not all Literates fault. There are a couple of problems:

1. There is not fallback _show method for the different backends (All backends should have a fallback for "text/plain" JuliaPlots/Plots.jl#1515)
2. UnicodePlots is simply broken in the notebook (UnicodePlots broken in IJulia JuliaPlots/Plots.jl#1514)
3. The last thing, which seems to be a bug in Literate is the serialization of image/svg+xml data, which I am trying to understand... (Edit: Its Plots shouldn't lie about output data JuliaPlots/Plots.jl#1529)

[mcabbott]

Thanks for taking a look, and opening issues on Plots. Sounds like 1 & 2 at least should be simple.

[fredrikekre]

Ok, the last thing seem to be because Plots.jl lies about what data it sends back, see JuliaPlots/Plots.jl#1529

[RoyiAvital]

Is there a way to get color in the MarkDown output of Literarte.jl for plots of UnicodePlots.jl?

[fredrikekre]

Does it work in Documenter?

[RoyiAvital]

Haven't tried. Just looking on a way creating a MarkDown file which is version control friendly.
So I thought on 2 options:

1. Using UnicodePlots.jl.
2. Pushing images to ImgUr then embedding by link.

Unfortunately ImgUr requires registration of the application etc...