// Test that Context.Log has a consistent function stack depth when binding
// log.Valuers, regardless of how many times Context.With has been called or
// whether Context.Log is called via an interface typed variable or a concrete
// typed variable.
func TestContextStackDepth(t *testing.T) {
t.Parallel()
fn := fmt.Sprintf("%n", stack.Caller(0))
var output []interface{}
logger := log.Logger(log.LoggerFunc(func(keyvals ...interface{}) error {
output = keyvals
return nil
}))
stackValuer := log.Valuer(func() interface{} {
for i, c := range stack.Trace() {
if fmt.Sprintf("%n", c) == fn {
return i
}
}
t.Fatal("Test function not found in stack trace.")
return nil
})
concrete := log.NewContext(logger).With("stack", stackValuer)
var iface log.Logger = concrete
// Call through interface to get baseline.
iface.Log("k", "v")
want := output[1].(int)
for len(output) < 10 {
concrete.Log("k", "v")
if have := output[1]; have != want {
t.Errorf("%d Withs: have %v, want %v", len(output)/2-1, have, want)
}
iface.Log("k", "v")
if have := output[1]; have != want {
t.Errorf("%d Withs: have %v, want %v", len(output)/2-1, have, want)
}
wrapped := log.NewContext(concrete)
wrapped.Log("k", "v")
if have := output[1]; have != want {
t.Errorf("%d Withs: have %v, want %v", len(output)/2-1, have, want)
}
concrete = concrete.With("k", "v")
iface = concrete
}
}
func Example_valuer() {
logger := log.NewLogfmtLogger(os.Stdout)
count := 0
counter := func() interface{} {
count++
return count
}
logger = log.NewContext(logger).With("count", log.Valuer(counter))
logger.Log("call", "first")
logger.Log("call", "second")
// Output:
// count=1 call=first
// count=2 call=second
}