allow custom log level names & colors

Author: IanButterworth

base/logging.jl

@@ -162,14 +162,19 @@ const AboveMaxLevel = LogLevel( 1000001)
 # Global log limiting mechanism for super fast but inflexible global log limiting.
 const _min_enabled_level = Ref{LogLevel}(Debug)
 
+# add to this to dict to introduce a log level for printing
+# i.e. custom_log_levels[LogLevel(-500)] = ("MyLog", :magenta)
+const custom_log_levels = Dict{LogLevel,Tuple{String,Symbol}}()
+
 function show(io::IO, level::LogLevel)
-    if     level == BelowMinLevel  print(io, "BelowMinLevel")
-    elseif level == Debug          print(io, "Debug")
-    elseif level == Info           print(io, "Info")
-    elseif level == Warn           print(io, "Warn")
-    elseif level == Error          print(io, "Error")
-    elseif level == AboveMaxLevel  print(io, "AboveMaxLevel")
-    else                           print(io, "LogLevel($(level.level))")
+    if     level in keys(custom_log_levels) print(io, custom_log_levels[level][1]::String)
+    elseif level == BelowMinLevel           print(io, "BelowMinLevel")
+    elseif level == Debug                   print(io, "Debug")
+    elseif level == Info                    print(io, "Info")
+    elseif level == Warn                    print(io, "Warn")
+    elseif level == Error                   print(io, "Error")
+    elseif level == AboveMaxLevel           print(io, "AboveMaxLevel")
+    else                                    print(io, "LogLevel($(level.level))")
     end
 end
 

stdlib/Logging/docs/src/index.md

@@ -58,7 +58,7 @@ automatically extracted. Let's examine the user-defined data first:
 * The *log level* is a broad category for the message that is used for early
   filtering. There are several standard levels of type [`LogLevel`](@ref);
   user-defined levels are also possible.
-  Each is distinct in purpose:
+  Each built-in is distinct in purpose:
   - [`Logging.Debug`](@ref) (log level -1000) is information intended for the developer of
     the program. These events are disabled by default.
   - [`Logging.Info`](@ref) (log level 0) is for general information to the user.
@@ -70,6 +70,15 @@ automatically extracted. Let's examine the user-defined data first:
     Often this log-level is unneeded as throwing an exception can convey
     all the required information.
 
+    You can also asign printing styles for custom log levels. For instance:
+    ```
+    MyLog = LogLevel(-500)
+    custom_log_levels[MyLog] = ("MyLog", :magenta)
+    macro mylog(exs...) Base.CoreLogging.logmsg_code((Base.CoreLogging.@_sourceinfo)..., MyLog, exs...) end
+
+    @mylog "foo"
+    ```
+
 * The *message*  is an object describing the event. By convention
   `AbstractString`s passed as messages are assumed to be in markdown format.
   Other types will be displayed using `print(io, obj)` or `string(obj)` for
@@ -298,6 +307,7 @@ Logging.Debug
 Logging.Info
 Logging.Warn
 Logging.Error
+Logging.custom_log_levels
 ```
 
 ### [Processing events with AbstractLogger](@id AbstractLogger-interface)

stdlib/Logging/src/ConsoleLogger.jl

@@ -58,6 +58,7 @@ end
 showvalue(io, ex::Exception) = showerror(io, ex)
 
 function default_logcolor(level::LogLevel)
+    level in keys(custom_log_levels) ? custom_log_levels[level][2]::Symbol :
     level < Info  ? Base.debug_color() :
     level < Warn  ? Base.info_color()  :
     level < Error ? Base.warn_color()  :

stdlib/Logging/src/Logging.jl

@@ -55,6 +55,18 @@ Alias for [`LogLevel(2000)`](@ref LogLevel).
 """
 const Error = Base.CoreLogging.Error
 
+"""
+    custom_log_levels::Dict{LogLevel,Tuple{String,Symbol}}
+
+Add to this dict to introduce a print style for a custom log.
+
+For instance:
+```
+custom_log_levels[LogLevel(-500)] = ("MyLog", :magenta)
+```
+"""
+const custom_log_levels = Base.CoreLogging.custom_log_levels
+
 using Base.CoreLogging:
     closed_stream
 

stdlib/Logging/test/runtests.jl

@@ -280,6 +280,7 @@ end
 end
 
 @testset "custom log macro" begin
+    Logging.custom_log_levels[CustomLog] = ("CustomLog", :magenta)
     @test_logs (CustomLog, "a") min_level=CustomLog @customlog "a"
 
     buf = IOBuffer()
@@ -289,7 +290,7 @@ end
     with_logger(logger) do
         @customlog "a"
     end
-    @test occursin("LogLevel(-500): a", String(take!(buf)))
+    @test occursin("CustomLog: a", String(take!(buf)))
 end
 
 end