handle exceptions in any key (#15)

Author: ericphanson

README.md

@@ -37,7 +37,7 @@ julia> with_logger(FormatLogger(LoggingFormats.JSON(; recursive=true), stderr))
 ```
 
 If it encounters something which does not have a defined `StructTypes.StructType` to use
-for serializing to JSON, it will fallback to converting the objects to strings, like the default `recursive=false` option does. Handles the key `exception` specially, by printing errors and stacktraces using `Base.showerror`.
+for serializing to JSON (or otherwise errors when serializing to JSON), it will fallback to converting the objects to strings, like the default `recursive=false` option does. Handles exceptions specially, by printing errors and stacktraces using `Base.showerror`.
 
 ```julia
 julia> f() = try
@@ -66,7 +66,7 @@ level=info msg="hello, world" module=Main file="REPL[2]" line=2 group="REPL[2]"
 level=error msg="something is wrong" module=Main file="REPL[2]" line=3 group="REPL[2]" id=Main_2289c7f8
 ```
 
-Similarly to the JSON logger, `LogFmt` handles the key `exception` specially, by printing errors and stacktraces using `Base.showerror`.
+Similarly to the JSON logger, `LogFmt` handles exceptions specially, by printing errors and stacktraces using `Base.showerror`.
 
 ## `Truncated`: Truncate long variables and messages
 

src/LoggingFormats.jl

@@ -70,21 +70,9 @@ end
 transform(::Type{String}, v) = string(v)
 transform(::Type{Any}, v) = v
 
-function maybe_stringify_exceptions(key, v)
-    key == :exception || return v
-    if v isa Tuple && length(v) == 2 && v[1] isa Exception
-        e, bt = v
-        msg = sprint(Base.display_error, e, bt)
-        return msg
-    end
-    return sprint(showerror, v)
-end
-
-# Use key information, then lower to 2-arg transform
-function transform(::Type{T}, key, v) where {T}
-    v = maybe_stringify_exceptions(key, v)
-    return transform(T, v)
-end
+maybe_stringify_exceptions((e, bt)::Tuple{Exception,Any}) = sprint(Base.display_error, e, bt)
+maybe_stringify_exceptions(e::Exception) = sprint(showerror, e)
+maybe_stringify_exceptions(v) = v
 
 function JSONLogMessage{T}(args) where {T}
     JSONLogMessage{T}(
@@ -95,7 +83,7 @@ function JSONLogMessage{T}(args) where {T}
         args.line,
         args.group === nothing ? nothing : string(args.group),
         args.id === nothing ? nothing : string(args.id),
-        Dict{String,T}(string(k) => transform(T, k, v) for (k, v) in args.kwargs)
+        Dict{String,T}(string(k) => transform(T, maybe_stringify_exceptions(v)) for (k, v) in args.kwargs)
     )
 end
 StructTypes.StructType(::Type{<:JSONLogMessage}) = StructTypes.OrderedStruct()
@@ -152,7 +140,7 @@ function (::LogFmt)(io, args)
     )
     for (k, v) in args.kwargs
         print(io, " ", k, "=\"")
-        v = maybe_stringify_exceptions(k, v)
+        v = maybe_stringify_exceptions(v)
         escape_string(io, sprint(print, something(v, "nothing")), '"')
         print(io, "\"")
     end

test/runtests.jl

@@ -134,16 +134,21 @@ end
         # no stacktrace
         io = IOBuffer()
         with_logger(FormatLogger(JSON(; recursive=recursive), io)) do
-            try
-                throw(ArgumentError("no"))
-            catch e
-                @error "Oh no" exception = e
-            end
+            @error "Oh no" exception = ArgumentError("no")
         end
         logs = JSON3.read(seekstart(io))
         @test logs["msg"] == "Oh no"
         @test logs["kwargs"]["exception"] == "ArgumentError: no"
 
+        # non-standard exception key
+        io = IOBuffer()
+        with_logger(FormatLogger(JSON(; recursive=recursive), io)) do
+            @error "Oh no" ex = ArgumentError("no")
+        end
+        logs = JSON3.read(seekstart(io))
+        @test logs["msg"] == "Oh no"
+        @test logs["kwargs"]["ex"] == "ArgumentError: no"
+
         # stacktrace
         io = IOBuffer()
         with_logger(FormatLogger(JSON(; recursive=recursive), io)) do