[log] proper impl of With for filter

log/filter.go

@@ -45,7 +45,7 @@ func (l *filter) Error(msg string, keyvals ...interface{}) error {
 }
 
 func (l *filter) With(keyvals ...interface{}) Logger {
-	return l.next.With(keyvals...)
+	return &filter{next: l.next.With(keyvals...), allowed: l.allowed, errNotAllowed: l.errNotAllowed}
 }
 
 // Option sets a parameter for the filter.

log/filter_test.go

@@ -93,11 +93,17 @@ func TestLevelContext(t *testing.T) {
 
 	var logger log.Logger
 	logger = log.NewTMJSONLogger(&buf)
-	logger = log.NewFilter(logger, log.AllowAll())
+	logger = log.NewFilter(logger, log.AllowError())
 	logger = logger.With("context", "value")
 
+	logger.Error("foo", "bar", "baz")
+	if want, have := `{"_msg":"foo","bar":"baz","context":"value","level":"error"}`, strings.TrimSpace(buf.String()); want != have {
+		t.Errorf("\nwant '%s'\nhave '%s'", want, have)
+	}
+
+	buf.Reset()
 	logger.Info("foo", "bar", "baz")
-	if want, have := `{"_msg":"foo","bar":"baz","context":"value","level":"info"}`, strings.TrimSpace(buf.String()); want != have {
+	if want, have := ``, strings.TrimSpace(buf.String()); want != have {
 		t.Errorf("\nwant '%s'\nhave '%s'", want, have)
 	}
 }