all: replace log15 with slog (#28187)

This PR replaces Geth's logger package (a fork of [log15](https://github.com/inconshreveable/log15)) with an implementation using slog, a logging library included as part of the Go standard library as of Go1.21.

Main changes are as follows:
* removes any log handlers that were unused in the Geth codebase.
* Json, logfmt, and terminal formatters are now slog handlers.
* Verbosity level constants are changed to match slog constant values.  Internal translation is done to make this opaque to the user and backwards compatible with existing `--verbosity` and `--vmodule` options.
* `--log.backtraceat` and `--log.debug` are removed.

The external-facing API is largely the same as the existing Geth logger.  Logger method signatures remain unchanged.

A small semantic difference is that a `Handler` can only be set once per `Logger` and not changed dynamically.  This just means that a new logger must be instantiated every time the handler of the root logger is changed.

----
For users of the `go-ethereum/log` module. If you were using this module for your own project, you will need to change the initialization. If you previously did 
```golang
log.Root().SetHandler(log.LvlFilterHandler(log.LvlInfo, log.StreamHandler(os.Stderr, log.TerminalFormat(true))))
```
You now instead need to do 
```golang
log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(os.Stderr, log.LevelInfo, true)))
```
See more about reasoning here: #28558 (comment)

Author: jwasinger

cmd/abigen/main.go

@@ -232,7 +232,7 @@ func abigen(c *cli.Context) error {
 }
 
 func main() {
-	log.Root().SetHandler(log.LvlFilterHandler(log.LvlInfo, log.StreamHandler(os.Stderr, log.TerminalFormat(true))))
+	log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(os.Stderr, log.LevelInfo, true)))
 
 	if err := app.Run(os.Args); err != nil {
 		fmt.Fprintln(os.Stderr, err)

cmd/bootnode/main.go

@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/nat"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
+	"golang.org/x/exp/slog"
 )
 
 func main() {
@@ -52,10 +53,10 @@ func main() {
 	)
 	flag.Parse()
 
-	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat(false)))
-	glogger.Verbosity(log.Lvl(*verbosity))
+	glogger := log.NewGlogHandler(log.NewTerminalHandler(os.Stderr, false))
+	glogger.Verbosity(slog.Level(*verbosity))
 	glogger.Vmodule(*vmodule)
-	log.Root().SetHandler(glogger)
+	log.SetDefault(log.NewLogger(glogger))
 
 	natm, err := nat.Parse(*natdesc)
 	if err != nil {

cmd/clef/main.go

@@ -57,6 +57,7 @@ import (
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"github.com/urfave/cli/v2"
+	"golang.org/x/exp/slog"
 )
 
 const legalWarning = `
@@ -492,7 +493,7 @@ func initialize(c *cli.Context) error {
 	if usecolor {
 		output = colorable.NewColorable(logOutput)
 	}
-	log.Root().SetHandler(log.LvlFilterHandler(log.Lvl(c.Int(logLevelFlag.Name)), log.StreamHandler(output, log.TerminalFormat(usecolor))))
+	log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(output, slog.Level(c.Int(logLevelFlag.Name)), usecolor)))
 
 	return nil
 }

cmd/devp2p/runtest.go

@@ -54,7 +54,7 @@ func runTests(ctx *cli.Context, tests []utesting.Test) error {
 	}
 	// Disable logging unless explicitly enabled.
 	if !ctx.IsSet("verbosity") && !ctx.IsSet("vmodule") {
-		log.Root().SetHandler(log.DiscardHandler())
+		log.SetDefault(log.NewLogger(log.DiscardHandler()))
 	}
 	// Run the tests.
 	var run = utesting.RunTests

cmd/evm/internal/t8ntool/block.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/urfave/cli/v2"
+	"golang.org/x/exp/slog"
 )
 
 //go:generate go run github.com/fjl/gencodec -type header -field-override headerMarshaling -out gen_header.go
@@ -216,9 +217,9 @@ func (i *bbInput) sealClique(block *types.Block) (*types.Block, error) {
 // BuildBlock constructs a block from the given inputs.
 func BuildBlock(ctx *cli.Context) error {
 	// Configure the go-ethereum logger
-	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat(false)))
-	glogger.Verbosity(log.Lvl(ctx.Int(VerbosityFlag.Name)))
-	log.Root().SetHandler(glogger)
+	glogger := log.NewGlogHandler(log.NewTerminalHandler(os.Stderr, false))
+	glogger.Verbosity(slog.Level(ctx.Int(VerbosityFlag.Name)))
+	log.SetDefault(log.NewLogger(glogger))
 
 	baseDir, err := createBasedir(ctx)
 	if err != nil {

cmd/evm/internal/t8ntool/transaction.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/tests"
 	"github.com/urfave/cli/v2"
+	"golang.org/x/exp/slog"
 )
 
 type result struct {
@@ -66,9 +67,9 @@ func (r *result) MarshalJSON() ([]byte, error) {
 
 func Transaction(ctx *cli.Context) error {
 	// Configure the go-ethereum logger
-	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat(false)))
-	glogger.Verbosity(log.Lvl(ctx.Int(VerbosityFlag.Name)))
-	log.Root().SetHandler(glogger)
+	glogger := log.NewGlogHandler(log.NewTerminalHandler(os.Stderr, false))
+	glogger.Verbosity(slog.Level(ctx.Int(VerbosityFlag.Name)))
+	log.SetDefault(log.NewLogger(glogger))
 
 	var (
 		err error

cmd/evm/internal/t8ntool/transition.go

@@ -24,6 +24,8 @@ import (
 	"os"
 	"path"
 
+	"golang.org/x/exp/slog"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/consensus/misc/eip1559"
@@ -81,9 +83,9 @@ type input struct {
 
 func Transition(ctx *cli.Context) error {
 	// Configure the go-ethereum logger
-	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat(false)))
-	glogger.Verbosity(log.Lvl(ctx.Int(VerbosityFlag.Name)))
-	log.Root().SetHandler(glogger)
+	glogger := log.NewGlogHandler(log.NewTerminalHandler(os.Stderr, false))
+	glogger.Verbosity(slog.Level(ctx.Int(VerbosityFlag.Name)))
+	log.SetDefault(log.NewLogger(glogger))
 
 	var (
 		err    error

cmd/geth/logging_test.go

@@ -28,6 +28,7 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
+	"encoding/json"
 
 	"github.com/ethereum/go-ethereum/internal/reexec"
 )
@@ -98,6 +99,53 @@ func testConsoleLogging(t *testing.T, format string, tStart, tEnd int) {
 	}
 }
 
+func TestJsonLogging(t *testing.T) {
+	t.Parallel()
+	haveB, err := runSelf("--log.format", "json", "logtest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	readFile, err := os.Open("testdata/logging/logtest-json.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	wantLines := split(readFile)
+	haveLines := split(bytes.NewBuffer(haveB))
+	for i, wantLine := range wantLines {
+		if i > len(haveLines)-1 {
+			t.Fatalf("format %v, line %d missing, want:%v", "json", i, wantLine)
+		}
+		haveLine := haveLines[i]
+		for strings.Contains(haveLine, "Unknown config environment variable") {
+			// This can happen on CI runs. Drop it.
+			haveLines = append(haveLines[:i], haveLines[i+1:]...)
+			haveLine = haveLines[i]
+		}
+		var have, want []byte
+		{
+			var h map[string]any
+			if err := json.Unmarshal([]byte(haveLine), &h); err != nil {
+				t.Fatal(err)
+			}
+			h["t"] = "xxx"
+			have, _ = json.Marshal(h)
+		}
+		{
+			var w map[string]any
+			if err := json.Unmarshal([]byte(wantLine), &w); err != nil {
+				t.Fatal(err)
+			}
+			w["t"] = "xxx"
+			want, _ = json.Marshal(w)
+		}
+		if !bytes.Equal(have, want) {
+			// show an intelligent diff
+			t.Logf(nicediff(have, want))
+			t.Errorf("file content wrong")
+		}
+	}
+}
+
 func TestVmodule(t *testing.T) {
 	t.Parallel()
 	checkOutput := func(level int, want, wantNot string) {

cmd/geth/logtestcmd_active.go

@@ -26,6 +26,7 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/internal/debug"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/holiman/uint256"
 	"github.com/urfave/cli/v2"
@@ -49,7 +50,9 @@ func (c customQuotedStringer) String() string {
 // logTest is an entry point which spits out some logs. This is used by testing
 // to verify expected outputs
 func logTest(ctx *cli.Context) error {
-	log.ResetGlobalState()
+	// clear field padding map
+	debug.ResetLogging()
+
 	{ // big.Int
 		ba, _ := new(big.Int).SetString("111222333444555678999", 10)    // "111,222,333,444,555,678,999"
 		bb, _ := new(big.Int).SetString("-111222333444555678999", 10)   // "-111,222,333,444,555,678,999"

cmd/geth/main.go

@@ -144,6 +144,8 @@ var (
 		utils.GpoMaxGasPriceFlag,
 		utils.GpoIgnoreGasPriceFlag,
 		configFileFlag,
+		utils.LogDebugFlag,
+		utils.LogBacktraceAtFlag,
 	}, utils.NetworkFlags, utils.DatabaseFlags)
 
 	rpcFlags = []cli.Flag{