all: replace strings.Split with strings.SplitSeq

In Go 1.25+, strings.SplitSeq offers better
performance. Here are the benchmark results comparing
strings.Split and strings.SplitSeq in a for-loop, with the
benchmark code located in src/strings/iter_test.go:

goos: darwin
goarch: amd64
pkg: cmd/go/internal/auth
cpu: Intel(R) Core(TM) i7-8569U CPU @ 2.80GHz
                         │   old.txt   │               new.txt                │
                         │   sec/op    │    sec/op     vs base                │
ParseGitAuth/standard-8    281.4n ± 1%   218.0n ± 11%  -22.54% (p=0.000 n=10)
ParseGitAuth/with_url-8    549.1n ± 1%   480.5n ± 13%  -12.48% (p=0.002 n=10)
ParseGitAuth/minimal-8     235.4n ± 1%   197.3n ±  7%  -16.20% (p=0.000 n=10)
ParseGitAuth/complex-8     797.6n ± 2%   805.2n ±  4%        ~ (p=0.481 n=10)
ParseGitAuth/empty-8       87.48n ± 3%   63.25n ±  6%  -27.71% (p=0.000 n=10)
ParseGitAuth/malformed-8   228.8n ± 1%   171.2n ±  3%  -25.17% (p=0.000 n=10)
geomean                    288.9n        237.7n        -17.72%

                         │   old.txt   │              new.txt               │
                         │    B/op     │    B/op     vs base                │
ParseGitAuth/standard-8    192.00 ± 0%   96.00 ± 0%  -50.00% (p=0.000 n=10)
ParseGitAuth/with_url-8     400.0 ± 0%   288.0 ± 0%  -28.00% (p=0.000 n=10)
ParseGitAuth/minimal-8     144.00 ± 0%   80.00 ± 0%  -44.44% (p=0.000 n=10)
ParseGitAuth/complex-8      528.0 ± 0%   400.0 ± 0%  -24.24% (p=0.000 n=10)
ParseGitAuth/empty-8        32.00 ± 0%   16.00 ± 0%  -50.00% (p=0.000 n=10)
ParseGitAuth/malformed-8   176.00 ± 0%   80.00 ± 0%  -54.55% (p=0.000 n=10)
geomean                     179.0        102.1       -42.96%

                         │  old.txt   │              new.txt               │
                         │ allocs/op  │ allocs/op   vs base                │
ParseGitAuth/standard-8    3.000 ± 0%   2.000 ± 0%  -33.33% (p=0.000 n=10)
ParseGitAuth/with_url-8    4.000 ± 0%   3.000 ± 0%  -25.00% (p=0.000 n=10)
ParseGitAuth/minimal-8     3.000 ± 0%   2.000 ± 0%  -33.33% (p=0.000 n=10)
ParseGitAuth/complex-8     4.000 ± 0%   3.000 ± 0%  -25.00% (p=0.000 n=10)
ParseGitAuth/empty-8       2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.000 n=10)
ParseGitAuth/malformed-8   3.000 ± 0%   2.000 ± 0%  -33.33% (p=0.000 n=10)
geomean                    3.086        2.040       -33.91%

Updates #69315.

Change-Id: Id0219edea45d9658d527b863162ebe917e7821d9
GitHub-Last-Rev: 392b315
GitHub-Pull-Request: #75259
Reviewed-on: https://go-review.googlesource.com/c/go/+/701015
Reviewed-by: Keith Randall <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Emmanuel Odeke <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Emmanuel Odeke <[email protected]>

Author: 1911860538

misc/ios/go_ios_exec.go

@@ -212,7 +212,7 @@ func copyLocalData(dstbase string) (pkgpath string, err error) {
 	// Copy all immediate files and testdata directories between
 	// the package being tested and the source root.
 	pkgpath = ""
-	for _, element := range strings.Split(finalPkgpath, string(filepath.Separator)) {
+	for element := range strings.SplitSeq(finalPkgpath, string(filepath.Separator)) {
 		if debug {
 			log.Printf("copying %s", pkgpath)
 		}

src/cmd/cgo/gcc.go

@@ -251,7 +251,7 @@ func (f *File) loadDefines(gccOptions []string) bool {
 	stdout := gccDefines(b.Bytes(), gccOptions)
 
 	var gccIsClang bool
-	for _, line := range strings.Split(stdout, "\n") {
+	for line := range strings.SplitSeq(stdout, "\n") {
 		if len(line) < 9 || line[0:7] != "#define" {
 			continue
 		}
@@ -428,7 +428,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 		notDeclared
 	)
 	sawUnmatchedErrors := false
-	for _, line := range strings.Split(stderr, "\n") {
+	for line := range strings.SplitSeq(stderr, "\n") {
 		// Ignore warnings and random comments, with one
 		// exception: newer GCC versions will sometimes emit
 		// an error on a macro #define with a note referring

src/cmd/cgo/internal/test/testx.go

@@ -447,7 +447,7 @@ func issue7978check(t *testing.T, wantFunc string, badFunc string, depth int) {
 	runtime.GC()
 	buf := make([]byte, 65536)
 	trace := string(buf[:runtime.Stack(buf, true)])
-	for _, goroutine := range strings.Split(trace, "\n\n") {
+	for goroutine := range strings.SplitSeq(trace, "\n\n") {
 		if strings.Contains(goroutine, "test.issue7978go") {
 			trace := strings.Split(goroutine, "\n")
 			// look for the expected function in the stack

src/cmd/compile/internal/base/flag.go

@@ -570,7 +570,7 @@ func readEmbedCfg(file string) {
 
 // parseSpectre parses the spectre configuration from the string s.
 func parseSpectre(s string) {
-	for _, f := range strings.Split(s, ",") {
+	for f := range strings.SplitSeq(s, ",") {
 		f = strings.TrimSpace(f)
 		switch f {
 		default:

src/cmd/dist/build.go

@@ -380,7 +380,7 @@ func findgoversion() string {
 		if i := strings.Index(b, "\n"); i >= 0 {
 			rest := b[i+1:]
 			b = chomp(b[:i])
-			for _, line := range strings.Split(rest, "\n") {
+			for line := range strings.SplitSeq(rest, "\n") {
 				f := strings.Fields(line)
 				if len(f) == 0 {
 					continue
@@ -1137,7 +1137,7 @@ func shouldbuild(file, pkg string) bool {
 	}
 
 	// Check file contents for //go:build lines.
-	for _, p := range strings.Split(readfile(file), "\n") {
+	for p := range strings.SplitSeq(readfile(file), "\n") {
 		p = strings.TrimSpace(p)
 		if p == "" {
 			continue
@@ -2016,7 +2016,7 @@ func cmdlist() {
 }
 
 func setNoOpt() {
-	for _, gcflag := range strings.Split(gogcflags, " ") {
+	for gcflag := range strings.SplitSeq(gogcflags, " ") {
 		if gcflag == "-N" || gcflag == "-l" {
 			noOpt = true
 			break

src/cmd/distpack/pack.go

@@ -271,7 +271,7 @@ func readVERSION(goroot string) (version string, t time.Time) {
 		log.Fatal(err)
 	}
 	version, rest, _ := strings.Cut(string(data), "\n")
-	for _, line := range strings.Split(rest, "\n") {
+	for line := range strings.SplitSeq(rest, "\n") {
 		f := strings.Fields(line)
 		if len(f) == 0 {
 			continue

src/cmd/fix/main.go

@@ -84,14 +84,14 @@ func main() {
 
 	if *allowedRewrites != "" {
 		allowed = make(map[string]bool)
-		for _, f := range strings.Split(*allowedRewrites, ",") {
+		for f := range strings.SplitSeq(*allowedRewrites, ",") {
 			allowed[f] = true
 		}
 	}
 
 	if *forceRewrites != "" {
 		force = make(map[string]bool)
-		for _, f := range strings.Split(*forceRewrites, ",") {
+		for f := range strings.SplitSeq(*forceRewrites, ",") {
 			force[f] = true
 		}
 	}

src/cmd/go/internal/auth/gitauth.go

@@ -82,7 +82,7 @@ func runGitAuth(client *http.Client, dir, url string) (string, http.Header, erro
 // Any of these values may be empty if parsing fails.
 func parseGitAuth(data []byte) (parsedPrefix, username, password string) {
 	prefix := new(url.URL)
-	for _, line := range strings.Split(string(data), "\n") {
+	for line := range strings.SplitSeq(string(data), "\n") {
 		key, value, ok := strings.Cut(strings.TrimSpace(line), "=")
 		if !ok {
 			continue

src/cmd/go/internal/auth/gitauth_test.go

@@ -5,6 +5,7 @@
 package auth
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -82,3 +83,77 @@ password:secr3t
 		}
 	}
 }
+
+func BenchmarkParseGitAuth(b *testing.B) {
+	// Define different test scenarios to benchmark
+	testCases := []struct {
+		name string
+		data []byte
+	}{{
+		// Standard scenario with all basic fields present
+		name: "standard",
+		data: []byte(`
+protocol=https
+host=example.com
+username=bob
+password=secr3t
+`),
+	}, {
+		// Scenario with URL field included
+		name: "with_url",
+		data: []byte(`
+protocol=https
+host=example.com
+username=bob
+password=secr3t
+url=https://example.com/repo
+`),
+	}, {
+		// Minimal scenario with only required fields
+		name: "minimal",
+		data: []byte(`
+protocol=https
+host=example.com
+`),
+	}, {
+		// Complex scenario with longer values and extra fields
+		name: "complex",
+		data: func() []byte {
+			var builder strings.Builder
+			builder.WriteString("protocol=https\n")
+			builder.WriteString("host=example.com\n")
+			builder.WriteString("username=longusernamenamename\n")
+			builder.WriteString("password=longpasswordwithmanycharacters123456789\n")
+			builder.WriteString("url=https://example.com/very/long/path/to/repository\n")
+			builder.WriteString("extra1=value1\n")
+			builder.WriteString("extra2=value2\n")
+			return []byte(builder.String())
+		}(),
+	}, {
+		// Scenario with empty input
+		name: "empty",
+		data: []byte(``),
+	}, {
+		// Scenario with malformed input (using colon instead of equals)
+		name: "malformed",
+		data: []byte(`
+protocol:https
+host:example.com
+username:bob
+password:secr3t
+`),
+	}}
+
+	for _, tc := range testCases {
+		b.Run(tc.name, func(b *testing.B) {
+			b.ResetTimer()
+			for b.Loop() {
+				prefix, username, password := parseGitAuth(tc.data)
+
+				_ = prefix
+				_ = username
+				_ = password
+			}
+		})
+	}
+}

src/cmd/go/internal/auth/netrc.go

@@ -24,7 +24,7 @@ func parseNetrc(data string) []netrcLine {
 	var nrc []netrcLine
 	var l netrcLine
 	inMacro := false
-	for _, line := range strings.Split(data, "\n") {
+	for line := range strings.SplitSeq(data, "\n") {
 		if inMacro {
 			if line == "" {
 				inMacro = false