cmd/go/internal/toolchain: revert "make a best effort to parse 'go run' and 'go install' flags"

This caused other problems, and for the purposes of the Go 1.22
release, we can just roll back to the Go 1.21 behavior and then
decide in January what the correct path forward is.

Revert of CL 546635.

Unfixes #64282.
Fixes #64738.
For #57001.

This reverts commit e44b8b15b19058b7a22a859ab4159f924856f688.

Change-Id: I78753c76dcd0bc6dbc90caa17f73248c42e5f64a
Reviewed-on: https://go-review.googlesource.com/c/go/+/551215
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Than McIntosh <thanm@google.com>

10 files changed, 45 insertions, 91 deletions

diff --git a/src/cmd/go/internal/base/goflags.go b/src/cmd/go/internal/base/goflags.go
index 3d5a76d54b..eced2c5d58 100644
--- a/src/cmd/go/internal/base/goflags.go
+++ b/src/cmd/go/internal/base/goflags.go
@@ -88,7 +88,7 @@ type boolFlag interface {
 }
 
 // SetFromGOFLAGS sets the flags in the given flag set using settings in $GOFLAGS.
-func SetFromGOFLAGS(flags *flag.FlagSet, ignoreErrors bool) {
+func SetFromGOFLAGS(flags *flag.FlagSet) {
 	InitGOFLAGS()
 
 	// This loop is similar to flag.Parse except that it ignores
@@ -121,22 +121,22 @@ func SetFromGOFLAGS(flags *flag.FlagSet, ignoreErrors bool) {
 
 		if fb, ok := f.Value.(boolFlag); ok && fb.IsBoolFlag() {
 			if hasValue {
-				if err := flags.Set(f.Name, value); err != nil && !ignoreErrors {
+				if err := flags.Set(f.Name, value); err != nil {
 					fmt.Fprintf(flags.Output(), "go: invalid boolean value %q for flag %s (from %s): %v\n", value, name, where, err)
 					flags.Usage()
 				}
 			} else {
-				if err := flags.Set(f.Name, "true"); err != nil && !ignoreErrors {
+				if err := flags.Set(f.Name, "true"); err != nil {
 					fmt.Fprintf(flags.Output(), "go: invalid boolean flag %s (from %s): %v\n", name, where, err)
 					flags.Usage()
 				}
 			}
 		} else {
-			if !hasValue && !ignoreErrors {
+			if !hasValue {
 				fmt.Fprintf(flags.Output(), "go: flag needs an argument: %s (from %s)\n", name, where)
 				flags.Usage()
 			}
-			if err := flags.Set(f.Name, value); err != nil && !ignoreErrors {
+			if err := flags.Set(f.Name, value); err != nil {
 				fmt.Fprintf(flags.Output(), "go: invalid value %q for flag %s (from %s): %v\n", value, name, where, err)
 				flags.Usage()
 			}
diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index b3c77dfbc2..eeab6da62a 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -525,7 +525,7 @@ func readGoSum(dst map[module.Version][]string, file string, data []byte) {
 				// ignore malformed line so that go mod tidy can fix go.sum
 				continue
 			} else {
-				base.Fatalf("go: malformed go.sum:\n%s:%d: wrong number of fields %v\n", file, lineno, len(f))
+				base.Fatalf("malformed go.sum:\n%s:%d: wrong number of fields %v\n", file, lineno, len(f))
 			}
 		}
 		if f[2] == emptyGoModHash {
@@ -574,32 +574,32 @@ func checkMod(ctx context.Context, mod module.Version) {
 	// Do the file I/O before acquiring the go.sum lock.
 	ziphash, err := CachePath(ctx, mod, "ziphash")
 	if err != nil {
-		base.Fatalf("go: verifying %v", module.VersionError(mod, err))
+		base.Fatalf("verifying %v", module.VersionError(mod, err))
 	}
 	data, err := lockedfile.Read(ziphash)
 	if err != nil {
-		base.Fatalf("go: verifying %v", module.VersionError(mod, err))
+		base.Fatalf("verifying %v", module.VersionError(mod, err))
 	}
 	data = bytes.TrimSpace(data)
 	if !isValidSum(data) {
 		// Recreate ziphash file from zip file and use that to check the mod sum.
 		zip, err := CachePath(ctx, mod, "zip")
 		if err != nil {
-			base.Fatalf("go: verifying %v", module.VersionError(mod, err))
+			base.Fatalf("verifying %v", module.VersionError(mod, err))
 		}
 		err = hashZip(mod, zip, ziphash)
 		if err != nil {
-			base.Fatalf("go: verifying %v", module.VersionError(mod, err))
+			base.Fatalf("verifying %v", module.VersionError(mod, err))
 		}
 		return
 	}
 	h := string(data)
 	if !strings.HasPrefix(h, "h1:") {
-		base.Fatalf("go: verifying %v", module.VersionError(mod, fmt.Errorf("unexpected ziphash: %q", h)))
+		base.Fatalf("verifying %v", module.VersionError(mod, fmt.Errorf("unexpected ziphash: %q", h)))
 	}
 
 	if err := checkModSum(mod, h); err != nil {
-		base.Fatal(err)
+		base.Fatalf("%s", err)
 	}
 }
 
@@ -684,7 +684,7 @@ func haveModSumLocked(mod module.Version, h string) bool {
 			return true
 		}
 		if strings.HasPrefix(vh, "h1:") {
-			base.Fatalf("go: verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, sumFileName, vh)
+			base.Fatalf("verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, sumFileName, vh)
 		}
 	}
 	// Also check workspace sums.
@@ -696,7 +696,7 @@ func haveModSumLocked(mod module.Version, h string) bool {
 			if h == vh {
 				foundMatch = true
 			} else if strings.HasPrefix(vh, "h1:") {
-				base.Fatalf("go: verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, goSumFile, vh)
+				base.Fatalf("verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, goSumFile, vh)
 			}
 		}
 	}
@@ -895,7 +895,7 @@ func TrimGoSum(keep map[module.Version]bool) {
 	defer goSum.mu.Unlock()
 	inited, err := initGoSum()
 	if err != nil {
-		base.Fatal(err)
+		base.Fatalf("%s", err)
 	}
 	if !inited {
 		return
diff --git a/src/cmd/go/internal/test/testflag.go b/src/cmd/go/internal/test/testflag.go
index 22c3ab1302..425378889d 100644
--- a/src/cmd/go/internal/test/testflag.go
+++ b/src/cmd/go/internal/test/testflag.go
@@ -222,7 +222,7 @@ func (f *shuffleFlag) Set(value string) error {
 //	go test fmt -custom-flag-for-fmt-test
 //	go test -x math
 func testFlags(args []string) (packageNames, passToTest []string) {
-	base.SetFromGOFLAGS(&CmdTest.Flag, false)
+	base.SetFromGOFLAGS(&CmdTest.Flag)
 	addFromGOFLAGS := map[string]bool{}
 	CmdTest.Flag.Visit(func(f *flag.Flag) {
 		if short := strings.TrimPrefix(f.Name, "test."); passFlagToTest[short] {
diff --git a/src/cmd/go/internal/toolchain/exec.go b/src/cmd/go/internal/toolchain/exec.go
index acfb9e943c..820fe93e87 100644
--- a/src/cmd/go/internal/toolchain/exec.go
+++ b/src/cmd/go/internal/toolchain/exec.go
@@ -44,12 +44,12 @@ func execGoToolchain(gotoolchain, dir, exe string) {
 				if e.ProcessState.Exited() {
 					os.Exit(e.ProcessState.ExitCode())
 				}
-				base.Fatalf("go: exec %s: %s", gotoolchain, e.ProcessState)
+				base.Fatalf("exec %s: %s", gotoolchain, e.ProcessState)
 			}
-			base.Fatalf("go: exec %s: %s", exe, err)
+			base.Fatalf("exec %s: %s", exe, err)
 		}
 		os.Exit(0)
 	}
 	err := syscall.Exec(exe, os.Args, os.Environ())
-	base.Fatalf("go: exec %s: %v", gotoolchain, err)
+	base.Fatalf("exec %s: %v", gotoolchain, err)
 }
diff --git a/src/cmd/go/internal/toolchain/select.go b/src/cmd/go/internal/toolchain/select.go
index 84fa7f685c..9fd1549a61 100644
--- a/src/cmd/go/internal/toolchain/select.go
+++ b/src/cmd/go/internal/toolchain/select.go
@@ -8,10 +8,10 @@ package toolchain
 import (
 	"context"
 	"errors"
-	"flag"
 	"fmt"
 	"go/build"
 	"io/fs"
+	"log"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -20,12 +20,10 @@ import (
 
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
-	"cmd/go/internal/cmdflag"
 	"cmd/go/internal/gover"
 	"cmd/go/internal/modfetch"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/run"
-	"cmd/go/internal/work"
 
 	"golang.org/x/mod/module"
 )
@@ -87,6 +85,9 @@ func FilterEnv(env []string) []string {
 // It must be called early in startup.
 // See https://go.dev/doc/toolchain#select.
 func Select() {
+	log.SetPrefix("go: ")
+	defer log.SetPrefix("")
+
 	if !modload.WillBeEnabled() {
 		return
 	}
@@ -132,15 +133,15 @@ func Select() {
 			v := gover.FromToolchain(min)
 			if v == "" {
 				if plus {
-					base.Fatalf("go: invalid GOTOOLCHAIN %q: invalid minimum toolchain %q", gotoolchain, min)
+					base.Fatalf("invalid GOTOOLCHAIN %q: invalid minimum toolchain %q", gotoolchain, min)
 				}
-				base.Fatalf("go: invalid GOTOOLCHAIN %q", gotoolchain)
+				base.Fatalf("invalid GOTOOLCHAIN %q", gotoolchain)
 			}
 			minToolchain = min
 			minVers = v
 		}
 		if plus && suffix != "auto" && suffix != "path" {
-			base.Fatalf("go: invalid GOTOOLCHAIN %q: only version suffixes are +auto and +path", gotoolchain)
+			base.Fatalf("invalid GOTOOLCHAIN %q: only version suffixes are +auto and +path", gotoolchain)
 		}
 		mode = suffix
 	}
@@ -171,7 +172,7 @@ func Select() {
 				// has a suffix like "go1.21.1-foo" and toolchain is "go1.21.1".)
 				toolVers := gover.FromToolchain(toolchain)
 				if toolVers == "" || (!strings.HasPrefix(toolchain, "go") && !strings.Contains(toolchain, "-go")) {
-					base.Fatalf("go: invalid toolchain %q in %s", toolchain, base.ShortPath(file))
+					base.Fatalf("invalid toolchain %q in %s", toolchain, base.ShortPath(file))
 				}
 				if gover.Compare(toolVers, minVers) > 0 {
 					gotoolchain = toolchain
@@ -193,7 +194,7 @@ func Select() {
 	// so that we have initialized gover.Startup for use in error messages.
 	if target := os.Getenv(targetEnv); target != "" && TestVersionSwitch != "loop" {
 		if gover.LocalToolchain() != target {
-			base.Fatalf("go: toolchain %v invoked to provide %v", gover.LocalToolchain(), target)
+			base.Fatalf("toolchain %v invoked to provide %v", gover.LocalToolchain(), target)
 		}
 		os.Unsetenv(targetEnv)
 
@@ -224,7 +225,7 @@ func Select() {
 	// We want to disallow mistakes / bad ideas like GOTOOLCHAIN=bash,
 	// since we will find that in the path lookup.
 	if !strings.HasPrefix(gotoolchain, "go1") && !strings.Contains(gotoolchain, "-go1") {
-		base.Fatalf("go: invalid GOTOOLCHAIN %q", gotoolchain)
+		base.Fatalf("invalid GOTOOLCHAIN %q", gotoolchain)
 	}
 
 	Exec(gotoolchain)
@@ -243,6 +244,8 @@ var TestVersionSwitch string
 // as a source of Go toolchains. Otherwise Exec tries the PATH but then downloads
 // a toolchain if necessary.
 func Exec(gotoolchain string) {
+	log.SetPrefix("go: ")
+
 	writeBits = sysWriteBits()
 
 	count, _ := strconv.Atoi(os.Getenv(countEnv))
@@ -250,7 +253,7 @@ func Exec(gotoolchain string) {
 		fmt.Fprintf(os.Stderr, "go: switching from go%v to %v [depth %d]\n", gover.Local(), gotoolchain, count)
 	}
 	if count >= maxSwitch {
-		base.Fatalf("go: too many toolchain switches")
+		base.Fatalf("too many toolchain switches")
 	}
 	os.Setenv(countEnv, fmt.Sprint(count+1))
 
@@ -273,7 +276,7 @@ func Exec(gotoolchain string) {
 	case "loop", "mismatch":
 		exe, err := os.Executable()
 		if err != nil {
-			base.Fatal(err)
+			base.Fatalf("%v", err)
 		}
 		execGoToolchain(gotoolchain, os.Getenv("GOROOT"), exe)
 	}
@@ -288,7 +291,7 @@ func Exec(gotoolchain string) {
 	// GOTOOLCHAIN=auto looks in PATH and then falls back to download.
 	// GOTOOLCHAIN=path only looks in PATH.
 	if pathOnly {
-		base.Fatalf("go: cannot find %q in PATH", gotoolchain)
+		base.Fatalf("cannot find %q in PATH", gotoolchain)
 	}
 
 	// Set up modules without an explicit go.mod, to download distribution.
@@ -307,9 +310,9 @@ func Exec(gotoolchain string) {
 	dir, err := modfetch.Download(context.Background(), m)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
-			base.Fatalf("go: download %s for %s/%s: toolchain not available", gotoolchain, runtime.GOOS, runtime.GOARCH)
+			base.Fatalf("download %s for %s/%s: toolchain not available", gotoolchain, runtime.GOOS, runtime.GOARCH)
 		}
-		base.Fatalf("go: download %s: %v", gotoolchain, err)
+		base.Fatalf("download %s: %v", gotoolchain, err)
 	}
 
 	// On first use after download, set the execute bits on the commands
@@ -318,7 +321,7 @@ func Exec(gotoolchain string) {
 	if runtime.GOOS != "windows" {
 		info, err := os.Stat(filepath.Join(dir, "bin/go"))
 		if err != nil {
-			base.Fatalf("go: download %s: %v", gotoolchain, err)
+			base.Fatalf("download %s: %v", gotoolchain, err)
 		}
 		if info.Mode()&0111 == 0 {
 			// allowExec sets the exec permission bits on all files found in dir.
@@ -339,7 +342,7 @@ func Exec(gotoolchain string) {
 					return nil
 				})
 				if err != nil {
-					base.Fatalf("go: download %s: %v", gotoolchain, err)
+					base.Fatalf("download %s: %v", gotoolchain, err)
 				}
 			}
 
@@ -381,7 +384,7 @@ func Exec(gotoolchain string) {
 			err = raceSafeCopy(srcUGoMod, srcGoMod)
 		}
 		if err != nil {
-			base.Fatalf("go: download %s: %v", gotoolchain, err)
+			base.Fatalf("download %s: %v", gotoolchain, err)
 		}
 	}
 
@@ -472,7 +475,7 @@ func modGoToolchain() (file, goVers, toolchain string) {
 
 	data, err := os.ReadFile(file)
 	if err != nil {
-		base.Fatal(err)
+		base.Fatalf("%v", err)
 	}
 	return file, gover.GoModLookup(data, "go"), gover.GoModLookup(data, "toolchain")
 }
@@ -489,7 +492,6 @@ func goInstallVersion() bool {
 
 	// Check for pkg@version.
 	var arg string
-	var cmdFlags *flag.FlagSet
 	switch os.Args[1] {
 	default:
 		return false
@@ -498,7 +500,6 @@ func goInstallVersion() bool {
 		// across a toolchain switch. To make that work, assume the pkg@version
 		// is the last argument and skip the flag parsing.
 		arg = os.Args[len(os.Args)-1]
-		cmdFlags = &work.CmdInstall.Flag
 	case "run":
 		// For run, the pkg@version can be anywhere on the command line,
 		// because it is preceded by run flags and followed by arguments to the
@@ -506,7 +507,6 @@ func goInstallVersion() bool {
 		// flags a little bit, to know whether each flag takes an optional argument.
 		// We can still allow unknown flags as long as they have an explicit =value.
 		args := os.Args[2:]
-		cmdFlags = &run.CmdRun.Flag
 		for i := 0; i < len(args); i++ {
 			a := args[i]
 			if !strings.HasPrefix(a, "-") {
@@ -554,20 +554,6 @@ func goInstallVersion() bool {
 		return false
 	}
 
-	// Make a best effort to parse flags so that module flags like -modcacherw
-	// will take effect (see https://go.dev/issue/64282).
-	args := os.Args[2:]
-	for len(args) > 0 {
-		var err error
-		_, args, err = cmdflag.ParseOne(cmdFlags, args)
-		if errors.Is(err, cmdflag.ErrFlagTerminator) {
-			break
-		}
-		// Ignore all other errors: they may be new flags — or updated syntax for
-		// existing flags — intended for a newer Go toolchain.
-	}
-	base.SetFromGOFLAGS(cmdFlags, true)
-
 	// It would be correct to simply return true here, bypassing use
 	// of the current go.mod or go.work, and let "go run" or "go install"
 	// do the rest, including a toolchain switch.
diff --git a/src/cmd/go/internal/vet/vetflag.go b/src/cmd/go/internal/vet/vetflag.go
index 601ae9aa64..eb7af6508d 100644
--- a/src/cmd/go/internal/vet/vetflag.go
+++ b/src/cmd/go/internal/vet/vetflag.go
@@ -116,7 +116,7 @@ func vetFlags(args []string) (passToVet, packageNames []string) {
 
 	// Record the set of vet tool flags set by GOFLAGS. We want to pass them to
 	// the vet tool, but only if they aren't overridden by an explicit argument.
-	base.SetFromGOFLAGS(&CmdVet.Flag, false)
+	base.SetFromGOFLAGS(&CmdVet.Flag)
 	addFromGOFLAGS := map[string]bool{}
 	CmdVet.Flag.Visit(func(f *flag.Flag) {
 		if isVetFlag[f.Name] {
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index b309cb867a..d380aae489 100644
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -234,7 +234,7 @@ func invoke(cmd *base.Command, args []string) {
 	if cmd.CustomFlags {
 		args = args[1:]
 	} else {
-		base.SetFromGOFLAGS(&cmd.Flag, false)
+		base.SetFromGOFLAGS(&cmd.Flag)
 		cmd.Flag.Parse(args[1:])
 		args = cmd.Flag.Args()
 	}
diff --git a/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt b/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt
deleted file mode 100644
index ea644f789e..0000000000
--- a/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt
+++ /dev/null
@@ -1,32 +0,0 @@
-# Regression test for https://go.dev/issue/64282:
-# 'go install' and 'go run' with pkg@version arguments should make
-# a best effort to parse flags before they download modules to
-# identify which toolchain version to use, because those flags
-# may affect the downloaded contents.
-
-# However, the best-effort flag parsing should not interfere with
-# actual flag parsing if we don't switch toolchains. In particular,
-# unrecognized flags should still be diagnosed after the module for
-# the requested package has been downloaded and checked for toolchain
-# upgrades.
-
-! go install -cake=delicious -modcacherw example.com/printversion@v0.1.0
-stderr '^flag provided but not defined: -cake$'
-
-[!short] go install -modcacherw example.com/printversion@v0.1.0
-	# Because the -modcacherw flag was set, we should be able to modify the contents
-	# of a directory within the module cache.
-cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
-
-
-# We should also apply flags from GOFLAGS at this step.
-
-go clean -modcache
-env GOFLAGS=-modcacherw
-! go install -cake=delicious example.com/printversion@v0.1.0
-stderr '^flag provided but not defined: -cake$'
-cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
-
-
--- $WORK/extraneous.txt --
-This is not a Go source file.
diff --git a/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt b/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
index 35fad29193..23c41beae9 100644
--- a/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
+++ b/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
@@ -1,5 +1,5 @@
 ! go mod download
-stderr '^go: malformed go.sum:\n.*go.sum:3: wrong number of fields 5\n$'
+stderr '^malformed go.sum:\n.*go.sum:3: wrong number of fields 5\n$'
 
 go mod tidy
 cmp go.sum go.sum.after-tidy
diff --git a/src/cmd/go/testdata/script/work_sum_mismatch.txt b/src/cmd/go/testdata/script/work_sum_mismatch.txt
index d4997aa372..ca5d71dc5e 100644
--- a/src/cmd/go/testdata/script/work_sum_mismatch.txt
+++ b/src/cmd/go/testdata/script/work_sum_mismatch.txt
@@ -4,7 +4,7 @@
 cmpenv stderr want-error
 
 -- want-error --
-go: verifying rsc.io/sampler@v1.3.0/go.mod: checksum mismatch
+verifying rsc.io/sampler@v1.3.0/go.mod: checksum mismatch
 	downloaded: h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
 	$WORK${/}gopath${/}src${/}a${/}go.sum:     h1:U1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
 
@@ -58,4 +58,4 @@ import (
 
 func main() {
 	fmt.Println(quote.Hello())
-}
+}
\ No newline at end of file