add @create_log_macro for easily making log macros

NEWS.md

@@ -116,6 +116,11 @@ Standard library changes
    argument is the output of `bunchkaufman` or `lu` ([#50471]).
 * Structured matrices now retain either the axes of the parent (for `Symmetric`/`Hermitian`/`AbstractTriangular`/`UpperHessenberg`), or that of the principal diagonal (for banded matrices) ([#52480]).
 
+#### Logging
+* New `@create_log_macro` macro for creating new log macros like `@info`, `@warn` etc. For instance
+  `@create_log_macro MyLog 1500 :magenta` will create `@mylog` to be used like `@mylog "hello"` which
+  will show as `┌ MyLog: hello` etc. ([#52196])
+
 #### Printf
 
 #### Profile

base/logging.jl

@@ -162,12 +162,10 @@ 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}}()
+const custom_log_levels = Dict{LogLevel,Tuple{Symbol,Union{Symbol,Int}}}()
 
 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 +692,33 @@ end
 
 _global_logstate = LogState(SimpleLogger())
 
+"""
+    @create_log_macro(name::Symbol, level::Int, color::Union{Int,Symbol})
+
+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
+```
+"""
+macro create_log_macro(name, level, color)
+    macro_name = Symbol(lowercase(string(name)))
+    macro_string = QuoteNode(name)
+    loglevel = LogLevel(level)
+    quote
+        custom_log_levels[$(esc(loglevel))] = ($(macro_string), $(esc(color)))
+        macro $(esc(macro_name))(exs...)
+            $logmsg_code(($@_sourceinfo)..., $(esc(loglevel)), exs...)
+        end
+    end
+end
+
 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/ConsoleLogger.jl

@@ -58,7 +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 in keys(custom_log_levels) ? custom_log_levels[level][2] :
     level < Info  ? Base.debug_color() :
     level < Warn  ? Base.info_color()  :
     level < Error ? Base.warn_color()  :

stdlib/Logging/src/Logging.jl

@@ -21,6 +21,7 @@ for sym in [
     Symbol("@warn"),
     Symbol("@error"),
     Symbol("@logmsg"),
+    Symbol("@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
@@ -280,17 +276,27 @@ end
 end
 
 @testset "custom log macro" begin
-    Logging.custom_log_levels[CustomLog] = ("CustomLog", :magenta)
-    @test_logs (CustomLog, "a") min_level=CustomLog @customlog "a"
+    @create_log_macro CustomLog -500 :magenta
+
+    llevel = LogLevel(-500)
+
+    @test_logs (llevel, "a") min_level=llevel @customlog "a"
 
     buf = IOBuffer()
     io = IOContext(buf, :displaysize=>(30,80), :color=>false)
-    logger = ConsoleLogger(io, CustomLog)
+    logger = ConsoleLogger(io, llevel)
 
     with_logger(logger) do
         @customlog "a"
     end
     @test occursin("CustomLog: a", String(take!(buf)))
+
+    @create_log_macro CustomLog2 1500 1
+
+    with_logger(logger) do
+        @customlog2 "hello"
+    end
+    @test occursin("CustomLog2: a", String(take!(buf)))
 end
 
 end