Compilation message with MPI extension

Project.toml

@@ -2,3 +2,15 @@ name = "TrixiBase"
 uuid = "9a0f1c46-06d5-4909-a5a3-ce25d3fa3284"
 authors = ["Michael Schlottke-Lakemper <[email protected]>"]
 version = "0.1.0"
+
+[weakdeps]
+MPI = "da04e1cc-30fd-572f-bb4f-1f8673147195"
+
+[extensions]
+TrixiBaseMPIExt = "MPI"
+
+[compat]
+julia = "1.8"
+
+[extras]
+MPI = "da04e1cc-30fd-572f-bb4f-1f8673147195"

ext/TrixiBaseMPIExt.jl

@@ -0,0 +1,21 @@
+# Package extension for adding MPI-based features to TrixiBase.jl
+module TrixiBaseMPIExt
+__precompile__(false)
+
+# Load package extension code on Julia v1.9 and newer
+if isdefined(Base, :get_extension)
+    using MPI: MPI
+end
+import TrixiBase
+
+# This is a really working version - assuming the same
+# communication pattern etc. used in Trixi.jl.
+function TrixiBase.mpi_isparallel()
+    if MPI.Initialized()
+        return MPI.Comm_size(MPI.COMM_WORLD) > 1
+    else
+        return false
+    end
+end
+
+end

src/trixi_include.jl

@@ -39,6 +39,10 @@ function trixi_include(mod::Module, elixir::AbstractString; kwargs...)
         find_assignment(expr, key)
     end
 
+    # Print information on potential wait time only in non-parallel case
+    if !mpi_isparallel()
+        @info "You just called `trixi_include`. Julia may now compile the code, please be patient."
+    end
     Base.include(ex -> replace_assignments(insert_maxiters(ex); kwargs...), mod, elixir)
 end
 
@@ -143,3 +147,8 @@ function find_assignment(expr, destination)
 
     result
 end
+
+# This is just a dummy function. We only implement a real
+# version if MPI.jl is loaded to avoid letting TrixiBase.jl
+# depend explicitly on MPI.jl.
+mpi_isparallel() = false

test/dummy.jl

@@ -0,0 +1 @@
+println("Hello")