Add tools to simplify exceptions

Author: oschulz

src/ParallelProcessingTools.jl

@@ -17,6 +17,7 @@ using Logging: @logmsg, LogLevel, Info, Debug
 
 using Parameters: @with_kw
 
+include("exceptions.jl")
 include("fileio.jl")
 include("threadsafe.jl")
 include("threadlocal.jl")

src/exceptions.jl

@@ -0,0 +1,50 @@
+# This file is a part of ParallelProcessingTools.jl, licensed under the MIT License (MIT).
+
+"""
+    ParallelProcessingTools.original_exception(err)
+
+Replaces `TaskFailedException`s and `RemoteException`s with the underlying
+exception that originated within the task or on the remote process.
+"""
+function original_exception end
+
+original_exception(err) = err
+original_exception(err::CompositeException) = CompositeException(original_exception.(err.exceptions))
+original_exception(err::TaskFailedException) = err.task.result
+original_exception(err::RemoteException) = err.captured.ex
+
+
+"""
+    ParallelProcessingTools.onlyfirst_exception(err)
+
+Replaces `CompositeException`s with their first exception.
+
+Also employs `original_exception` if `simplify` is `true`.
+"""
+function onlyfirst_exception end
+
+onlyfirst_exception(err) = err
+onlyfirst_exception(err::CompositeException) = first(err.exceptions)
+
+
+"""
+    @userfriendly_exceptions expr
+
+Transforms exceptions originating from `expr` into more user-friendly ones.
+
+If multiple exceptions originate from parallel code in `expr`, only one
+is rethrown, and `TaskFailedException`s and `RemoteException`s are replaced
+by the original exceptions that caused them.
+
+See [`original_exception`] and [`onlyfirst_exception`](@ref).
+"""
+macro userfriendly_exceptions(expr)
+    quote
+        try
+            $(esc(expr))
+        catch err
+            rethrow(original_exception(onlyfirst_exception(err)))
+        end
+    end
+end
+export @userfriendly_exceptions