Merge pull request #469 from Liozou/precompilationbackgroundtask

Fix precompilation of packages depending on PlotlyJS

src/PlotlyJS.jl

@@ -95,7 +95,7 @@ function __init__()
         @warn("Warnings were generated during the last build of PlotlyJS:  please check the build log at $_build_log")
     end
 
-    @async _start_kaleido_process()
+    kaleido_task = Base.Threads.@spawn _start_kaleido_process()
 
     if !isfile(_js_path)
         @info("plotly.js javascript libary not found -- downloading now")
@@ -163,6 +163,16 @@ function __init__()
             dataset(::Type{DataFrames.DataFrame}, name::String) = DataFrames.DataFrame(dataset(CSV.File, name))
         end
     end
+
+    wait(kaleido_task)
+
+    if ccall(:jl_generating_output, Cint, ()) == 1
+        # ensure precompilation of packages depending on PlotlyJS finishes
+        if isdefined(P, :proc)
+            close(P.stdin)
+            wait(P.proc)
+        end
+    end
 end
 
 # for methods that update the layout, first apply to the plot, then let plotly.js