Append context in stdio backend.

Cleanup context on specs that changes it

spec/std/log/context_spec.cr

@@ -45,13 +45,15 @@ describe Log::Context do
       Log.context.set a: 1
       Log.context.set b: 2
       Log.context.should eq(c({a: 1, b: 2}))
+      Log.context.clear
     end
 
     it "existing keys are overwritten by set" do
       Log.context.clear
       Log.context.set a: 1, b: 1
       Log.context.set b: 2, c: 3
       Log.context.should eq(c({a: 1, b: 2, c: 3}))
+      Log.context.clear
     end
 
     it "is restored with using" do
@@ -64,6 +66,7 @@ describe Log::Context do
       end
 
       Log.context.should eq(c({a: 1}))
+      Log.context.clear
     end
 
     it "is per fiber" do
@@ -83,6 +86,7 @@ describe Log::Context do
       done.send nil
       Log.context.should eq(c({a: 1}))
       done.send nil
+      Log.context.clear
     end
   end
 end

spec/std/log/log_spec.cr

@@ -98,5 +98,7 @@ describe Log do
     log.info { "info message" }
 
     backend.entries.first.context.should eq(Log::Context.new({a: 1}))
+
+    Log.context.clear
   end
 end

spec/std/log/stdio_backend_spec.cr

@@ -40,6 +40,19 @@ describe Log::StdioBackend do
     end
   end
 
+  it "logs context" do
+    IO.pipe do |r, w|
+      logger = stdio_logger(stdout: w)
+      Log.context.clear
+      Log.context.using do
+        Log.context.set foo: "foo"
+        logger.info { "info:show" }
+      end
+
+      r.gets.should match(/info:show -- {:foo => "foo"}/)
+    end
+  end
+
   it "logs any object" do
     IO.pipe do |r, w|
       logger = stdio_logger(stdout: w)

src/log/stdio_backend.cr

@@ -31,6 +31,9 @@ class Log::StdioBackend < Log::Backend
     label = entry.severity.to_s.upcase
     io << label[0] << ", [" << entry.timestamp << " #" << Process.pid << "] "
     io << label.rjust(7) << " -- " << @progname << ":" << entry.source << ": " << entry.message
+    if entry.context.size > 0
+      io << " -- " << entry.context
+    end
     if ex = entry.exception
       io << " -- " << ex.class << ": " << ex
     end