Add FirstMatchLogger

README.md

@@ -79,6 +79,7 @@ This package introduces 6 new loggers.
 The `TeeLogger`, the `TransformerLogger`, 3 types of filtered logger, and the `FileLogger`.
 All of them just wrap existing loggers.
  - The `TeeLogger` sends the logs to multiple different loggers.
+ - The `FirstMatchLogger` also sends the logs to multiple different loggers but to only at most one logger for each log.
  - The `TransformerLogger` applies a function to modify log messages before passing them on.
  - The 3 filter loggers are used to control if a message is written or not
      - The `MinLevelLogger` only allowes messages to pass that are above a given level of severity
@@ -100,6 +101,12 @@ It is up to those loggers to determine if they will accept it.
 Which they do using their methods for `shouldlog` and `min_enabled_level`.
 Or you can do, by wrapping them in a filtered logger  as discussed below.
 
+## `FirstMatchLogger`
+
+The `FirstMatchLogger` sends the log messages to multiple places, like `TeeLogger`.
+Unlike, `TeeLogger`, it only sends a log to at most one logger that can handle the
+log message.  The first match in the list of loggers is used.
+
 ## `FileLogger`
 The `FileLogger` does logging to file.
 It is just a convience wrapper around the base julia `SimpleLogger`,

src/LoggingExtras.jl

@@ -8,7 +8,7 @@ import Base.CoreLogging:
     AbstractLogger, SimpleLogger,
     handle_message, shouldlog, min_enabled_level, catch_exceptions
 
-export TeeLogger, TransformerLogger, FileLogger,
+export TeeLogger, FirstMatchLogger, TransformerLogger, FileLogger,
     ActiveFilteredLogger, EarlyFilteredLogger, MinLevelLogger
 
 

src/tee.jl

@@ -1,4 +1,6 @@
-struct TeeLogger{T<:NTuple{<:Any, AbstractLogger}} <: AbstractLogger
+abstract type AbstractTeeLogger <: AbstractLogger end
+
+struct TeeLogger{T<:NTuple{<:Any, AbstractLogger}} <: AbstractTeeLogger
     loggers::T
 end
 
@@ -26,14 +28,38 @@ function handle_message(demux::TeeLogger, args...; kwargs...)
     end
 end
 
-function shouldlog(demux::TeeLogger, args...)
+function shouldlog(demux::AbstractTeeLogger, args...)
     any(comp_shouldlog(logger, args...) for logger in demux.loggers)
 end
 
-function min_enabled_level(demux::TeeLogger)
+function min_enabled_level(demux::AbstractTeeLogger)
     minimum(min_enabled_level(logger) for logger in demux.loggers)
 end
 
-function catch_exceptions(demux::TeeLogger)
+function catch_exceptions(demux::AbstractTeeLogger)
     any(catch_exceptions(logger) for logger in demux.loggers)
 end
+
+
+struct FirstMatchLogger{T<:NTuple{<:Any,AbstractLogger}} <: AbstractTeeLogger
+    loggers::T
+end
+
+"""
+    FirstMatchLogger(loggers...)
+
+For each log message, invoke the first logger in `loggers` that
+matches with it; i.e., `min_enabled_level` is less than or equal to
+the log level and `shouldlog` returns `true`.
+"""
+function FirstMatchLogger(loggers::Vararg{AbstractLogger})
+    return FirstMatchLogger(loggers)
+end
+
+function handle_message(logger::FirstMatchLogger, args...; kwargs...)
+    for logger in logger.loggers
+        if comp_handle_message_check(logger, args...; kwargs...)
+            return handle_message(logger, args...; kwargs...)
+        end
+    end
+end

test/runtests.jl

@@ -31,6 +31,31 @@ using Base.CoreLogging: BelowMinLevel, Debug, Info, Warn, Error
 end
 
 
+@testset "FirstMatch" begin
+    @testset "contructor" begin
+        @testset "mixed types" begin
+            @test FirstMatchLogger(TestLogger(), NullLogger()) isa FirstMatchLogger
+        end
+
+        @testset "errors if given nonloggers" begin
+            @test_throws Exception FirstMatchLogger(stdout, stderr)
+        end
+    end
+    @testset "basic use with compositional levels" begin
+        testlogger_info = TestLogger(min_level=Info)
+        testlogger_warn = TestLogger(min_level=Warn)
+
+        with_logger(FirstMatchLogger(testlogger_warn, testlogger_info)) do
+            @info "info1"
+            @warn "warn1"
+            @info "info2"
+        end
+        @test length(testlogger_info.logs) == 2
+        @test length(testlogger_warn.logs) == 1
+    end
+end
+
+
 @testset "File" begin
     mktempdir() do dir
         filepath = joinpath(dir, "log")