feat(xattribute): add utility package for building attributes

internal/xattribute/pool.go

@@ -0,0 +1,29 @@
+package xattribute
+
+import "sync"
+
+type stringSlice struct {
+	val []string
+}
+
+func (s *stringSlice) Reset() {
+	s.val = s.val[:0]
+}
+
+var stringSlicePool = &sync.Pool{
+	New: func() any {
+		return &stringSlice{
+			val: make([]string, 0, 16),
+		}
+	},
+}
+
+func getStringSlice() *stringSlice {
+	ss := stringSlicePool.Get().(*stringSlice)
+	ss.Reset()
+	return ss
+}
+
+func putStringSlice(ss *stringSlice) {
+	stringSlicePool.Put(ss)
+}

internal/xattribute/xattribute.go

@@ -0,0 +1,53 @@
+// Package xattribute provides some helpers to create OpenTelemetry attributes.
+package xattribute
+
+import (
+	"fmt"
+	"slices"
+
+	"go.opentelemetry.io/otel/attribute"
+)
+
+// StringerSlice creates a string slice attribute from slice of [fmt.Stringer] implementations.
+func StringerSlice[S ~[]E, E fmt.Stringer](k string, v S) attribute.KeyValue {
+	if len(v) == 0 {
+		return attribute.StringSlice(k, nil)
+	}
+
+	// Using pooled string slice is fine, since attribute package copies slice.
+	ss := getStringSlice()
+	defer putStringSlice(ss)
+
+	ss.val = append(ss.val, make([]string, len(v))...)
+	for i, f := range v {
+		ss.val[i] = safeStringer(f)
+	}
+	return attribute.StringSlice(k, ss.val)
+}
+
+func safeStringer[F fmt.Stringer](f F) (v string) {
+	defer func() {
+		if r := recover(); r != nil {
+			v = "<stringer panic>:" + fmt.Sprint(r)
+		}
+	}()
+	return f.String()
+}
+
+// StringMap creates a sorted string slice attribute from string map.
+func StringMap(k string, m map[string]string) attribute.KeyValue {
+	if len(m) == 0 {
+		return attribute.StringSlice(k, nil)
+	}
+
+	// Using pooled string slice is fine, since attribute package copies slice.
+	ss := getStringSlice()
+	defer putStringSlice(ss)
+
+	for k, v := range m {
+		ss.val = append(ss.val, k+"="+v)
+	}
+	slices.Sort(ss.val)
+
+	return attribute.StringSlice(k, ss.val)
+}

internal/xattribute/xattribute_test.go

@@ -0,0 +1,97 @@
+package xattribute
+
+import (
+	"fmt"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel/attribute"
+)
+
+type justStringer struct{}
+
+func (justStringer) String() string {
+	return "justStringer"
+}
+
+type panicStringer struct{}
+
+func (panicStringer) String() string {
+	panic("bad stringer")
+}
+
+func TestStringerSlice(t *testing.T) {
+	tests := []struct {
+		k    string
+		v    []fmt.Stringer
+		want attribute.KeyValue
+	}{
+		{
+			"key",
+			nil,
+			attribute.StringSlice("key", nil),
+		},
+		{
+			"key",
+			[]fmt.Stringer{justStringer{}},
+			attribute.StringSlice("key", []string{"justStringer"}),
+		},
+		{
+			"key",
+			[]fmt.Stringer{panicStringer{}},
+			attribute.StringSlice("key", []string{"<stringer panic>:bad stringer"}),
+		},
+		{
+			"key",
+			[]fmt.Stringer{nil},
+			attribute.StringSlice("key", []string{"<stringer panic>:runtime error: invalid memory address or nil pointer dereference"}),
+		},
+	}
+	for i, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			require.Equal(t, tt.want, StringerSlice(tt.k, tt.v))
+		})
+	}
+}
+
+func BenchmarkStringerSlice(b *testing.B) {
+	var (
+		s    [4]justStringer
+		sink attribute.KeyValue
+	)
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		sink = StringerSlice("key", s[:])
+	}
+
+	runtime.KeepAlive(sink)
+}
+
+func TestStringMap(t *testing.T) {
+	tests := []struct {
+		k    string
+		m    map[string]string
+		want attribute.KeyValue
+	}{
+		{
+			"key",
+			nil,
+			attribute.StringSlice("key", nil),
+		},
+		{
+			"key",
+			map[string]string{"a": "1", "b": "2"},
+			attribute.StringSlice("key", []string{"a=1", "b=2"}),
+		},
+	}
+	for i, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			require.Equal(t, tt.want, StringMap(tt.k, tt.m))
+		})
+	}
+}