add Compat.at-error, Compat.at-warn, Compat.at-info and Compat.at-deb…

…ug (#458)

README.md

@@ -304,6 +304,17 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * `@nospecialize` has been added ([#22666]).
 
+* The logging macros `@error`, `@warn`, `@info` and `@debug` can be used as
+  `Compat.@error`, `Compat.@warn`, `Compat.@info` and `Compat.@debug` on Julia 0.6 ([#24490]).
+  Note that the behavior do not mirror the logging macros in Julia 0.7, instead on Julia 0.6:
+  - Messages are printed to `STDERR` (like `info` and `warn` on Julia 0.6) and not to a
+    dedicated logging stream.
+  - The loglevel can not be controlled, but `Compat.@debug` messages can be turned on/off
+    by calling `Compat.enable_debug(true/false)`.
+  - Extra metadata sent to the macros are ignored.
+
+  As an alternative, see the MicroLogging.jl package for a logging interface similar to the one in Julia 0.7.
+
 ## Other changes
 
 * On versions of Julia that do not contain a Base.Threads module, Compat defines a Threads module containing a no-op `@threads` macro.
@@ -432,6 +443,7 @@ includes this fix. Find the minimum version from there.
 [#24361]: https://github.com/JuliaLang/julia/issues/24361
 [#24372]: https://github.com/JuliaLang/julia/issues/24372
 [#24459]: https://github.com/JuliaLang/julia/issues/24459
+[#24490]: https://github.com/JuliaLang/julia/issues/24490
 [#24605]: https://github.com/JuliaLang/julia/issues/24605
 [#24647]: https://github.com/JuliaLang/julia/issues/24647
 [#24648]: https://github.com/JuliaLang/julia/issues/24648

src/Compat.jl

@@ -1235,6 +1235,54 @@ end
     end
 end
 
+@static if !isdefined(Base, Symbol("@info"))
+    macro info(msg, args...)
+        return :(info($(esc(msg)), prefix = "Info: "))
+    end
+else
+    @eval const $(Symbol("@info")) = Base.$(Symbol("@info"))
+end
+@static if !isdefined(Base, Symbol("@warn"))
+    macro warn(msg, args...)
+        return :(warn($(esc(msg)), prefix = "Warning: "))
+    end
+else
+    @eval const $(Symbol("@warn")) = Base.$(Symbol("@warn"))
+end
+
+const DEBUG = Ref(false) # debug printing off by default, as on 0.7
+enable_debug(x::Bool) = DEBUG[] = x
+@static if !isdefined(Base, Symbol("@debug"))
+    function debug(msg)
+        DEBUG[] || return
+        buf = IOBuffer()
+        iob = Base.redirect(IOContext(buf, STDERR), Base.log_info_to, :debug)
+        print_with_color(:blue, iob, "Debug: "; bold = true)
+        Base.println_with_color(:blue, iob, chomp(string(msg)))
+        print(STDERR, String(take!(buf)))
+        return
+    end
+    macro debug(msg, args...)
+        return :(debug($(esc(msg))))
+    end
+else
+    @eval const $(Symbol("@debug")) = Base.$(Symbol("@debug"))
+end
+@static if !isdefined(Base, Symbol("@error"))
+    function _error(msg)
+        buf = IOBuffer()
+        iob = Base.redirect(IOContext(buf, STDERR), Base.log_error_to, :error)
+        print_with_color(Base.error_color(), iob, "Error: "; bold = true)
+        Base.println_with_color(Base.error_color(), iob, chomp(string(msg)))
+        print(STDERR, String(take!(buf)))
+        return
+    end
+    macro error(msg, args...)
+        return :(_error($(esc(msg))))
+    end
+else
+    @eval const $(Symbol("@error")) = Base.$(Symbol("@error"))
+end
 
 include("deprecated.jl")
 

test/runtests.jl

@@ -1119,6 +1119,32 @@ let c = CartesianIndices(1:3, 1:2), l = LinearIndices(1:3, 1:2)
     @test l[vec(c)] == collect(1:6)
 end
 
+
+if !isdefined(Base, Symbol("@info"))
+    let fname = tempname()
+        try
+            open(fname, "w") do fout
+                redirect_stderr(fout) do
+                    Compat.@info  "A"
+                    Compat.@warn  "B"
+                    oldstate = Compat.DEBUG[]
+                    Compat.enable_debug(false)
+                    Compat.@debug "C"
+                    Compat.enable_debug(true)
+                    Compat.@debug "D"
+                    Compat.enable_debug(oldstate)
+                    Compat.@error "E"
+                end
+            end
+            @test read(fname, String) == (Base.have_color ? "\e[1m\e[36mInfo: \e[39m\e[22m\e[36mA\n\e[39m\e[1m\e[33mWarning: \e[39m\e[22m\e[33mB\e[39m\n\e[1m\e[34mDebug: \e[39m\e[22m\e[34mD\n\e[39m\e[1m\e[91mError: \e[39m\e[22m\e[91mE\n\e[39m" :
+                "Info: A\nWarning: B\nDebug: D\nError: E\n")
+        finally
+            rm(fname, force=true)
+        end
+    end
+end
+
+
 if VERSION < v"0.6.0"
     include("deprecated.jl")
 end