Possibly incorrect `displayable("text/html")` in v0.6

question

#1

This came up in the attempt to get Interact.jl working on v0.6-dev. It currently fails when trying to display some HTML. A MRE is:

if displayable("text/html")
    display("text/html", """foo""")
end

In the REPL in Julia v0.5, displayable("text/html") return false, which makes sense. In Julia v0.6-dev, however, it returns true in the REPL, which leads to errors when trying to actually display:

               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0-dev.2834 (2017-02-16 21:11 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit 3222749* (0 days old master)
|__/                   |  x86_64-apple-darwin15.6.0

julia> displayable("text/html")
true

julia> if displayable("text/html")
           display("text/html", """foo""")
       end
ERROR: MethodError: no method matching show(::Base.TTY, ::MIME{Symbol("text/html")}, ::String)
Closest candidates are:
  show(::IO, ::MIME{mime}) where mime at multimedia.jl:21
  show(::IO, ::ANY) at show.jl:125
  show(::IO, ::AbstractString, ::Any) at multimedia.jl:39
  ...
Stacktrace:
 [1] display(::TextDisplay, ::MIME{Symbol("text/html")}, ::String) at ./multimedia.jl:158
 [2] display(::MIME{Symbol("text/html")}, ::String) at ./multimedia.jl:208
 [3] display(::String, ::String) at ./multimedia.jl:126

Specifically, it’s the first display (the Base.TTY) that thinks it can display “text/html”:

   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0-dev.2834 (2017-02-16 21:11 UTC)
 _/ |\__'_|_|_|\__'_|  |  Commit 3222749* (0 days old master)
|__/                   |  x86_64-apple-darwin15.6.0

julia> displayable("text/html")
true

julia> displayable(Base.Multimedia.displays[1], "text/html")
true

julia> displayable(Base.Multimedia.displays[2], "text/html")
false

julia> Base.Multimedia.displays[1]
TextDisplay(Base.TTY(RawFD(14) open, 0 bytes waiting))

Is this a bug? Or is the package doing something wrong?


#2

BTW, git bisect shows that this change came in with 8950cf80


#3

Indeed the TextDisplay is able to display HTML; i.e.

julia> display("text/html", html"<p>Hello</p>")
<p>Hello</p>

so this is not really a bug. (Although this display is not so useful.) The reason the MethodError occurs is because String cannot be displayed as HTML.


#4

I see, thanks. I’ll fix that in Interact.