How to use the built-in InvalidStateException

Atiyah · June 8, 2022, 7:22am

What would be a typical use case for employing the built-in InvalidStateException?
Can this exception be employed for inconsistent values of different variables during runtime, i.e. invalid states or inconsistencies of different variable? Or is there a better option?
Throwing InvalidStateException requires two arguments a message and a symbol. What would be typical values of a symbol?

lawless-m · June 9, 2022, 5:31am

It is up to you when to throw it, one should match the words in the exception to the kind of error. The arguments are again, situation dependent and are most likely literals.

Here’s an example from the wild

github.com/julia-vscode/LanguageServer.jl

InvalidStateException("Channel is closed.", :closed)

opened 12:50AM - 18 Dec 21 UTC

laubblaeser

bug non-vscode

I've just tried to run LanguageServer and encountered the following error: ``…`julia julia> using LanguageServer julia> using LanguageServer.SymbolServer julia> runserver() ERROR: MethodError: no method matching (::LanguageServer.var"#93#95"{LanguageServerInstance})(::String, ::Int64) Closest candidates are: (::LanguageServer.var"#93#95")(::Any) at ~/.julia/packages/LanguageServer/JrIEf/src/languageserverinstance.jl:185 Stacktrace: [1] getstore(ssi::SymbolServerInstance, environment_path::String, progress_callback::LanguageServer.var"#93#95"{LanguageServerInstance}, error_handler::Nothing; download::Bool) @ SymbolServer ~/.julia/packages/SymbolServer/GBhfx/src/SymbolServer.jl:47 [2] macro expansion @ ~/.julia/packages/LanguageServer/JrIEf/src/languageserverinstance.jl:182 [inlined] [3] (::LanguageServer.var"#92#94"{LanguageServerInstance})() @ LanguageServer ./task.jl:423 ``` I'm on Julia 1.7 with LanguageServer 4.1.0. I've already ried to remove compiled/ and packages/ folders from ~/.julia/ but didn't help. Any ideas what's causing this?

Which if we trace back to where it is thrown

github.com

JuliaLang/julia/blob/742b9abb4dd4621b667ec5bb3434b8b3602f96fd/base/channels.jl#L163-L173


      
          closed_exception() = InvalidStateException("Channel is closed.", :closed)
          
          isbuffered(c::Channel) = c.sz_max==0 ? false : true
          
          function check_channel_state(c::Channel)
              if !isopen(c)
                  excp = c.excp
                  excp !== nothing && throw(excp)
                  throw(closed_exception())
              end
          end

and here’s the documentation for that call

https://docs.julialang.org/en/v1/base/parallel/#Base.take!-Tuple{Channel}

What seems to be different in Julia is the docs don’t mention that take! might throw and we have no way of annotating that. Meaning one day you might log in to find you didn’t use try in your long running code and you can make a sad face.