go.mod: bump minimum and language to 1.21 (#949)

* go.mod: bump minimum and language to 1.21

CI only tests Go 1.21 and 1.22, and older versions of Go are no longer
getting any bug or security fixes, so advertise that we only support
Go 1.21 or later via go.mod.

While here, ensure the module is tidy and resolve deprecation warnings,
and remove now-unnecessary Go version build tags.

* replace sort.Slice with slices.SortFunc

The latter is more efficient, and allocates less, since sort.Slice
needs to go through sort.Interface which causes allocations.

    goos: linux
    goarch: amd64
    pkg: github.com/pelletier/go-toml/v2/benchmark
    cpu: AMD Ryzen 7 PRO 5850U with Radeon Graphics
                              │     old     │                new                 │
                              │   sec/op    │   sec/op     vs base               │
    Marshal/HugoFrontMatter-8   7.612µ ± 1%   6.730µ ± 1%  -11.59% (p=0.002 n=6)

                              │     old      │                 new                 │
                              │     B/s      │     B/s       vs base               │
    Marshal/HugoFrontMatter-8   65.52Mi ± 1%   74.11Mi ± 1%  +13.11% (p=0.002 n=6)

                              │     old      │                new                 │
                              │     B/op     │     B/op      vs base              │
    Marshal/HugoFrontMatter-8   5.672Ki ± 0%   5.266Ki ± 0%  -7.16% (p=0.002 n=6)

                              │    old     │                new                │
                              │ allocs/op  │ allocs/op   vs base               │
    Marshal/HugoFrontMatter-8   85.00 ± 0%   73.00 ± 0%  -14.12% (p=0.002 n=6)

fuzz_test.go

@@ -1,6 +1,3 @@
-//go:build go1.18 || go1.19 || go1.20 || go1.21 || go1.22
-// +build go1.18 go1.19 go1.20 go1.21 go1.22
-
 package toml_test
 
 import (

go.mod

@@ -1,5 +1,11 @@
 module github.com/pelletier/go-toml/v2
 
-go 1.16
+go 1.21
 
 require github.com/stretchr/testify v1.9.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,19 +1,10 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

marshaler.go

@@ -8,7 +8,7 @@ import (
 	"io"
 	"math"
 	"reflect"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -280,7 +280,7 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 	}
 
 	hasTextMarshaler := v.Type().Implements(textMarshalerType)
-	if hasTextMarshaler || (v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
+	if hasTextMarshaler || (v.CanAddr() && reflect.PointerTo(v.Type()).Implements(textMarshalerType)) {
 		if !hasTextMarshaler {
 			v = v.Addr()
 		}
@@ -668,8 +668,8 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 }
 
 func sortEntriesByKey(e []entry) {
-	sort.Slice(e, func(i, j int) bool {
+	slices.SortFunc(e, func(a, b entry) int {
-		return e[i].Key < e[j].Key
+		return strings.Compare(a.Key, b.Key)
 	})
 }
 
@@ -951,7 +951,7 @@ func willConvertToTable(ctx encoderCtx, v reflect.Value) bool {
 	if !v.IsValid() {
 		return false
 	}
-	if v.Type() == timeType || v.Type().Implements(textMarshalerType) || (v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
+	if v.Type() == timeType || v.Type().Implements(textMarshalerType) || (v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PointerTo(v.Type()).Implements(textMarshalerType)) {
 		return false
 	}
 

ossfuzz/fuzz.go

@@ -1,6 +1,3 @@
-//go:build go1.18 || go1.19 || go1.20 || go1.21 || go1.22
-// +build go1.18 go1.19 go1.20 go1.21 go1.22
-
 package ossfuzz
 
 import (

unmarshaler.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math"
 	"reflect"
 	"strings"
@@ -117,7 +116,7 @@ func (d *Decoder) EnableUnmarshalerInterface() *Decoder {
 //	Inline Table     -> same as Table
 //	Array of Tables  -> same as Array and Table
 func (d *Decoder) Decode(v interface{}) error {
-	b, err := ioutil.ReadAll(d.r)
+	b, err := io.ReadAll(d.r)
 	if err != nil {
 		return fmt.Errorf("toml: %w", err)
 	}
@@ -1078,7 +1077,7 @@ func (d *decoder) keyFromData(keyType reflect.Type, data []byte) (reflect.Value,
 		}
 		return mk, nil
 
-	case reflect.PtrTo(keyType).Implements(textUnmarshalerType):
+	case reflect.PointerTo(keyType).Implements(textUnmarshalerType):
 		mk := reflect.New(keyType)
 		if err := mk.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
 			return reflect.Value{}, fmt.Errorf("toml: error unmarshalling key type %s from text: %w", stringType, err)