feat: support stack trace decorator

decorator.go

@@ -1,6 +1,8 @@
 package golog
 
 import (
+	"fmt"
+	"runtime"
 	"time"
 )
 
@@ -46,21 +48,42 @@ func (td TimestampDecorator) Decorate(e Entry) Entry {
 // StackTraceDecorator is a Decorator which add the log stacktrace
 type StackTraceDecorator struct {
 	StacktraceFieldName string
+	Depth               int
 }
 
 // NewStackTraceDecorator returns a StackTraceDecorator with the given field name
-func NewStackTraceDecorator(n string) StackTraceDecorator {
-	return StackTraceDecorator{StacktraceFieldName: n}
+func NewStackTraceDecorator(n string, depth int) StackTraceDecorator {
+	return StackTraceDecorator{StacktraceFieldName: n, Depth: depth}
 }
 
 // NewStackTraceDecoratorOption returns an Option which applies a StackTraceDecorator with the given field name
-func NewStackTraceDecoratorOption(n string) Option {
+func NewStackTraceDecoratorOption(n string, depth int) Option {
 	return OptionFunc(func(l StdLogger) StdLogger {
-		return l.WithDecorator(NewStackTraceDecorator(n))
+		return l.WithDecorator(NewStackTraceDecorator(n, depth))
 	})
 }
 
 // Decorate adds the stacktrace to the entry
 func (sd StackTraceDecorator) Decorate(e Entry) Entry {
-	return e.With(Fields{String(sd.StacktraceFieldName, "TODO")})
+	framesToField := func(fs *runtime.Frames) Field {
+		var trace []string
+		for {
+			f, ok := fs.Next()
+			trace = append(trace, fmt.Sprintf("%v:%v", f.File, f.Line))
+			if !ok {
+				break
+			}
+		}
+
+		return Strings(sd.StacktraceFieldName, trace)
+	}
+
+	const skip = 4
+	pc := make([]uintptr, sd.Depth)
+	if n := runtime.Callers(skip, pc[:]); n != 0 {
+		field := framesToField(runtime.CallersFrames(pc[:]))
+		return e.With(Fields{field})
+	}
+
+	return e
 }

decorator_test.go

@@ -0,0 +1,49 @@
+package golog_test
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	. "github.com/damianopetrungaro/golog"
+)
+
+func TestStackTraceDecorator_Decorate(t *testing.T) {
+	const fieldName = "stacktrace"
+
+	w := &FakeWriter{}
+	logger := New(w).WithDecorator(NewStackTraceDecorator(fieldName, 2))
+
+	wantStack := []string{
+		"/github.com/damianopetrungaro/golog/decorator_test.go:24",
+		"/usr/local/go/src/testing/testing.go:1439",
+	}
+
+	ctx := context.Background()
+
+	logger.With(Fields{String("hello", "world")}).Info(ctx, "An info message")
+	for _, f := range w.Entry.Fields() {
+		if f.Key() != fieldName {
+			continue
+		}
+		stack, ok := f.Value().([]string)
+		if !ok {
+			break
+		}
+
+		for i, trace := range stack {
+			if strings.HasSuffix(trace, "/github.com/damianopetrungaro/golog/decorator_test.go:24") {
+				stack[i] = "/github.com/damianopetrungaro/golog/decorator_test.go:24"
+			}
+		}
+
+		if strings.Join(stack, "##") != strings.Join(wantStack, "##") {
+			t.Error("could not match trace")
+			t.Errorf("got: %v", stack)
+			t.Errorf("want: %v", wantStack)
+		}
+
+		return
+	}
+	t.Error("could not find stacktrace field")
+}

golog.go

@@ -18,6 +18,7 @@ var (
 		),
 		levelChecker,
 		timestampDecorator,
+		stackTraceDecorator,
 	)
 
 	checkLogger CheckLogger = New(
@@ -29,14 +30,16 @@ var (
 		),
 		levelChecker,
 		timestampDecorator,
+		stackTraceDecorator,
 	)
 
 	errorHandler = func(err error) {
 		fmt.Println(fmt.Sprintf("golog: could not write: %s\n", err))
 	}
 
-	levelChecker       = NewLevelCheckerOption(INFO)
-	timestampDecorator = NewTimestampDecoratorOption("timestamp", time.RFC3339Nano)
+	levelChecker        = NewLevelCheckerOption(INFO)
+	timestampDecorator  = NewTimestampDecoratorOption("timestamp", time.RFC3339Nano)
+	stackTraceDecorator = NewStackTraceDecoratorOption("stacktrace", 5)
 )
 
 // Message is a log entry message