some logging things

 - use user customizable colors in logging
 - use showerror to print exceptions rather than their string representation
 - nice box drawing chars
 - print line info after key value pairs
 - always put the line info on its own line for multiline messages
[ci skip]

base/logging.jl

@@ -1,6 +1,7 @@
 module CoreLogging
 
 import Base: isless, +, -, convert, show
+using Base: info_color, warn_color, error_color
 
 export
     AbstractLogger,
@@ -341,8 +342,10 @@ end
         # Try really hard to get the message to the logger, with
         # progressively less information.
         try
-            msg = "Exception while generating log record in module $_module at $filepath:$line"
-            handle_message(logger, Error, msg, _module, group, id, filepath, line; exception=err)
+            msg = "Exception while generating log record:\n"
+            str = join("  " .* split(sprint(showerror, err), "\n"), "\n")
+            msg *= str
+            handle_message(logger, Error, msg, _module, group, id, filepath, line)
         catch err2
             try
                 # Give up and write to STDERR, in three independent calls to
@@ -482,19 +485,27 @@ function handle_message(logger::SimpleLogger, level, message, _module, group, id
     end
     levelstr = string(level)
     color = level < Info  ? :blue :
-            level < Warn  ? :cyan :
-            level < Error ? :yellow : :red
+            level < Warn  ? info_color() :
+            level < Error ? warn_color() : error_color()
     buf = IOBuffer()
-    print_with_color(color, buf, first(levelstr), "- ", bold=true)
-    msglines = split(string(message), '\n')
-    for i in 1:length(msglines)-1
-        println(buf, msglines[i])
-        print_with_color(color, buf, "|  ", bold=true)
-    end
-    println(buf, msglines[end], " -", levelstr, ":", _module, ":", basename(filepath), ":", line)
-    for (key,val) in pairs(kwargs)
-        print_with_color(color, buf, "|  ", bold=true)
-        println(buf, key, " = ", val)
+    msglines = split(chomp(string(message)), '\n')
+    if length(msglines) + length(kwargs) == 1
+        print_with_color(color, buf, first(levelstr), ": ", bold=true)
+        # print_with_color(color, buf, "- ")
+        println(buf, msglines[1], " - ", _module, ":", basename(filepath), ":", line)
+    else
+        print_with_color(color, buf, first(levelstr), "┌ ", bold=true)
+        println(buf, msglines[1])
+        for i in 2:length(msglines)
+            print_with_color(color, buf, " │ ", bold=true)
+            println(buf, msglines[i])
+        end
+        for (key,val) in pairs(kwargs)
+            print_with_color(color, buf, " │ ", bold=true)
+            println(buf, key, " = ", val)
+        end
+        print_with_color(color, buf, " └ ", bold=true)
+        println(buf, _module, ":", basename(filepath), ":", line)
     end
     write(logger.stream, take!(buf))
     nothing

base/replutil.jl

@@ -267,6 +267,7 @@ function showerror(io::IO, ex::DomainError, bt; backtrace=true)
     backtrace && show_backtrace(io, bt)
     nothing
 end
+showerror(io::IO, ex::DomainError) = showerror(io, ex, [])
 
 function showerror(io::IO, ex::SystemError)
     if ex.extrainfo === nothing