log/slog: implement encoding.TextAppender for Level and LevelVar

For #62384

Change-Id: I10df580ef966e497ff8da4efde6dd6ce1ccb17b4
GitHub-Last-Rev: 5ad8e2e0473ff509b48e525f6c7328f6281766a3
GitHub-Pull-Request: golang/go#68855
Reviewed-on: https://go-review.googlesource.com/c/go/+/605056
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/api/next/62384.txt b/api/next/62384.txt
index 37e0080a139ace1777efbacb29fc2127ec9005b7..ece5d9fd801445dc0b1bb8e288c1b861954382d6 100644 (file)
--- a/api/next/62384.txt
+++ b/api/next/62384.txt
@@ -3,3 +3,5 @@ pkg encoding, type BinaryAppender interface, AppendBinary([]uint8) ([]uint8, err
 pkg encoding, type TextAppender interface { AppendText } #62384
 pkg encoding, type TextAppender interface, AppendText([]uint8) ([]uint8, error) #62384
 pkg net/url, method (*URL) AppendBinary([]uint8) ([]uint8, error) #62384
+pkg log/slog, method (Level) AppendText([]uint8) ([]uint8, error) #62384
+pkg log/slog, method (*LevelVar) AppendText([]uint8) ([]uint8, error) #62384

diff --git a/doc/next/6-stdlib/99-minor/log/slog/62384.md b/doc/next/6-stdlib/99-minor/log/slog/62384.md
new file mode 100644 (file)
index 0000000..5f8cbaa
--- /dev/null
+++ b/doc/next/6-stdlib/99-minor/log/slog/62384.md
@@ -0,0 +1 @@
+[Level] and [LevelVar] now implement the [encoding.TextAppender] interface.\r

diff --git a/src/log/slog/level.go b/src/log/slog/level.go
index 7cddf4cfba5ca27fe036114e12aa7c69f92ee0f2..2957585e0e848c69e4cae724647f4dcbbb3c360a 100644 (file)
--- a/src/log/slog/level.go
+++ b/src/log/slog/level.go
@@ -98,10 +98,16 @@ func (l *Level) UnmarshalJSON(data []byte) error {
        return l.parse(s)
 }
 
-// MarshalText implements [encoding.TextMarshaler]
+// AppendText implements [encoding.TextAppender]
 // by calling [Level.String].
+func (l Level) AppendText(b []byte) ([]byte, error) {
+       return append(b, l.String()...), nil
+}
+
+// MarshalText implements [encoding.TextMarshaler]
+// by calling [Level.AppendText].
 func (l Level) MarshalText() ([]byte, error) {
-       return []byte(l.String()), nil
+       return l.AppendText(nil)
 }
 
 // UnmarshalText implements [encoding.TextUnmarshaler].
@@ -172,10 +178,16 @@ func (v *LevelVar) String() string {
        return fmt.Sprintf("LevelVar(%s)", v.Level())
 }
 
+// AppendText implements [encoding.TextAppender]
+// by calling [Level.AppendText].
+func (v *LevelVar) AppendText(b []byte) ([]byte, error) {
+       return v.Level().AppendText(b)
+}
+
 // MarshalText implements [encoding.TextMarshaler]
-// by calling [Level.MarshalText].
+// by calling [LevelVar.AppendText].
 func (v *LevelVar) MarshalText() ([]byte, error) {
-       return v.Level().MarshalText()
+       return v.AppendText(nil)
 }
 
 // UnmarshalText implements [encoding.TextUnmarshaler]

diff --git a/src/log/slog/level_test.go b/src/log/slog/level_test.go
index 217a0d7204915a5a87ec59be33240e91b8ae9e02..73be1126b275dc62e3bc7f905a9b7827dc92b928 100644 (file)
--- a/src/log/slog/level_test.go
+++ b/src/log/slog/level_test.go
@@ -89,6 +89,19 @@ func TestLevelMarshalText(t *testing.T) {
        }
 }
 
+func TestLevelAppendText(t *testing.T) {
+       buf := make([]byte, 4, 16)
+       want := LevelWarn - 3
+       wantData := []byte("\x00\x00\x00\x00INFO+1")
+       data, err := want.AppendText(buf)
+       if err != nil {
+               t.Fatal(err)
+       }
+       if !bytes.Equal(data, wantData) {
+               t.Errorf("got %s, want %s", string(data), string(wantData))
+       }
+}
+
 func TestLevelParse(t *testing.T) {
        for _, test := range []struct {
                in   string
@@ -162,6 +175,23 @@ func TestLevelVarMarshalText(t *testing.T) {
        }
 }
 
+func TestLevelVarAppendText(t *testing.T) {
+       var v LevelVar
+       v.Set(LevelWarn)
+       buf := make([]byte, 4, 16)
+       data, err := v.AppendText(buf)
+       if err != nil {
+               t.Fatal(err)
+       }
+       var v2 LevelVar
+       if err := v2.UnmarshalText(data[4:]); err != nil {
+               t.Fatal(err)
+       }
+       if g, w := v2.Level(), LevelWarn; g != w {
+               t.Errorf("got %s, want %s", g, w)
+       }
+}
+
 func TestLevelVarFlag(t *testing.T) {
        fs := flag.NewFlagSet("test", flag.ContinueOnError)
        v := &LevelVar{}