add create_log_macro for easily making log macros

Author: IanButterworth

base/logging.jl

@@ -163,11 +163,11 @@ const AboveMaxLevel = LogLevel( 1000001)
 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}}()
+# i.e. custom_log_levels[LogLevel(-500)] = (:mylog, :magenta)
+const custom_log_levels = Dict{LogLevel,Tuple{Symbol,Symbol}}()
 
 function show(io::IO, level::LogLevel)
-    if     level in keys(custom_log_levels) print(io, custom_log_levels[level][1]::String)
+    if     level in keys(custom_log_levels) print(io, custom_log_levels[level][1])
     elseif level == BelowMinLevel           print(io, "BelowMinLevel")
     elseif level == Debug                   print(io, "Debug")
     elseif level == Info                    print(io, "Info")
@@ -694,4 +694,35 @@ end
 
 _global_logstate = LogState(SimpleLogger())
 
+"""
+    create_log_macro(name::Symbol, level::Int, color::Union{Int,Symbol}=:default)
+    create_log_macro(name::Symbol, loglevel::LogLevel, color::Union{Int,Symbol}=:default)
+
+Creates a custom log macro like `@info`, `@warn` etc. with a given `name`, `level` and
+`color`. The macro created is named with the lowercase form of `name` but the given form
+is used for the printing.
+
+See `Base.text_colors` for recognized color values.
+
+```julia-repl
+julia> create_log_macro(:MyLog, 200, :magenta)
+@mylog (macro with 1 method)
+
+julia> @mylog "hello"
+[ MyLog: hello
+```
+"""
+function create_log_macro(name::Symbol, loglevel::LogLevel, color::Union{Int,Symbol}=:default)
+    haskey(Base.text_colors, color) || @warn "Color $(repr(color)) not recognized"
+    custom_log_levels[loglevel] = (name, color)
+    macro_name = Symbol(lowercase(string(name)))
+    @eval begin
+        macro $macro_name(exs...)
+            logmsg_code((@_sourceinfo)..., $loglevel, exs...)
+        end
+    end
+end
+create_log_macro(name::Symbol, level::Int, color::Union{Int,Symbol}=:default) =
+    create_log_macro(name, LogLevel(level), color)
+
 end # CoreLogging

stdlib/Logging/docs/src/index.md

@@ -70,13 +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
+    You can also create logging macros for custom log levels. For instance:
+    ```julia-repl
+    julia> using Logging
+
+    julia> create_log_macro(:MyLog, 200, :magenta)
+    @mylog (macro with 1 method)
 
-    @mylog "foo"
+    julia> @mylog "hello"
+    [ MyLog: hello
     ```
 
 * The *message*  is an object describing the event. By convention

stdlib/Logging/src/Logging.jl

@@ -21,6 +21,7 @@ for sym in [
     Symbol("@warn"),
     Symbol("@error"),
     Symbol("@logmsg"),
+    :create_log_macro,
     :with_logger,
     :current_logger,
     :global_logger,
@@ -79,6 +80,7 @@ export
     @warn,
     @error,
     @logmsg,
+    create_log_macro,
     with_logger,
     current_logger,
     global_logger,

stdlib/Logging/test/runtests.jl

@@ -6,10 +6,6 @@ import Logging: min_enabled_level, shouldlog, handle_message
 
 @noinline func1() = backtrace()
 
-# see "custom log macro" testset
-CustomLog = LogLevel(-500)
-macro customlog(exs...) Base.CoreLogging.logmsg_code((Base.CoreLogging.@_sourceinfo)..., esc(CustomLog), exs...) end
-
 @testset "Logging" begin
 
 @testset "Core" begin
@@ -280,7 +276,12 @@ end
 end
 
 @testset "custom log macro" begin
-    Logging.custom_log_levels[CustomLog] = ("CustomLog", :magenta)
+    CustomLog = LogLevel(-500)
+
+    # TODO: Figure out how to avoid the need to `var"@customlog" = `
+    # Maybe this should be a macro, but I couldn't figure out a macro creating a macro
+    var"@customlog" = create_log_macro("CustomLog", CustomLog, :magenta)
+
     @test_logs (CustomLog, "a") min_level=CustomLog @customlog "a"
 
     buf = IOBuffer()