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[release-branch.go1.22] cmd/go/internal/toolchain: apply the -modcach…
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…erw flag when downloading a module to determine what toolchain it needs

Fixes #64282.

Change-Id: I3f211c599ee70cb58254d0bc07eeb3c135124e58
Reviewed-on: https://go-review.googlesource.com/c/go/+/555436
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
(cherry picked from commit cc38c68)
Reviewed-on: https://go-review.googlesource.com/c/go/+/559218
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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Bryan C. Mills authored and gopherbot committed Jan 31, 2024
1 parent 117d7b1 commit aa721d1
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Showing 2 changed files with 149 additions and 44 deletions.
148 changes: 104 additions & 44 deletions src/cmd/go/internal/toolchain/select.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ package toolchain
import (
"context"
"errors"
"flag"
"fmt"
"go/build"
"io/fs"
Expand All @@ -24,6 +25,7 @@ import (
"cmd/go/internal/modfetch"
"cmd/go/internal/modload"
"cmd/go/internal/run"
"cmd/go/internal/work"

"golang.org/x/mod/module"
)
Expand Down Expand Up @@ -486,74 +488,132 @@ func goInstallVersion() bool {
// Note: We assume there are no flags between 'go' and 'install' or 'run'.
// During testing there are some debugging flags that are accepted
// in that position, but in production go binaries there are not.
if len(os.Args) < 3 || (os.Args[1] != "install" && os.Args[1] != "run") {
if len(os.Args) < 3 {
return false
}

// Check for pkg@version.
var arg string
var cmdFlags *flag.FlagSet
switch os.Args[1] {
default:
// Command doesn't support a pkg@version as the main module.
return false
case "install":
// We would like to let 'go install -newflag pkg@version' work even
// 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
// program being run. To handle that precisely, we have to interpret the
// 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:]
for i := 0; i < len(args); i++ {
a := args[i]
if !strings.HasPrefix(a, "-") {
arg = a
break
}
if a == "-" {
// non-flag but also non-pkg@version
cmdFlags = &run.CmdRun.Flag
}

// The modcachrw flag is unique, in that it affects how we fetch the
// requested module to even figure out what toolchain it needs.
// We need to actually set it before we check the toolchain version.
// (See https://go.dev/issue/64282.)
modcacherwFlag := cmdFlags.Lookup("modcacherw")
if modcacherwFlag == nil {
base.Fatalf("internal error: modcacherw flag not registered for command")
}
modcacherwVal, ok := modcacherwFlag.Value.(interface {
IsBoolFlag() bool
flag.Value
})
if !ok || !modcacherwVal.IsBoolFlag() {
base.Fatalf("internal error: modcacherw is not a boolean flag")
}

// Make a best effort to parse the command's args to find the pkg@version
// argument and the -modcacherw flag.
var (
pkgArg string
modcacherwSeen bool
)
for args := os.Args[2:]; len(args) > 0; {
a := args[0]
args = args[1:]
if a == "--" {
if len(args) == 0 {
return false
}
if a == "--" {
if i+1 >= len(args) {
return false
}
arg = args[i+1]
break
pkgArg = args[0]
break
}

a, ok := strings.CutPrefix(a, "-")
if !ok {
// Not a flag argument. Must be a package.
pkgArg = a
break
}
a = strings.TrimPrefix(a, "-") // Treat --flag as -flag.

name, val, hasEq := strings.Cut(a, "=")

if name == "modcacherw" {
if !hasEq {
val = "true"
}
a = strings.TrimPrefix(a, "-")
a = strings.TrimPrefix(a, "-")
if strings.HasPrefix(a, "-") {
// non-flag but also non-pkg@version
if err := modcacherwVal.Set(val); err != nil {
return false
}
if strings.Contains(a, "=") {
// already has value
continue
}
f := run.CmdRun.Flag.Lookup(a)
if f == nil {
// Unknown flag. Give up. The command is going to fail in flag parsing.
modcacherwSeen = true
continue
}

if hasEq {
// Already has a value; don't bother parsing it.
continue
}

f := run.CmdRun.Flag.Lookup(a)
if f == nil {
// We don't know whether this flag is a boolean.
if os.Args[1] == "run" {
// We don't know where to find the pkg@version argument.
// 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
// program being run. Since we don't know whether this flag takes
// an argument, we can't reliably identify the end of the run flags.
// Just give up and let the user clarify using the "=" form..
return false
}
if bf, ok := f.Value.(interface{ IsBoolFlag() bool }); ok && bf.IsBoolFlag() {
// Does not take value.
continue

// We would like to let 'go install -newflag pkg@version' work even
// across a toolchain switch. To make that work, assume by default that
// the pkg@version is the last argument and skip the remaining args unless
// we spot a plausible "-modcacherw" flag.
for len(args) > 0 {
a := args[0]
name, _, _ := strings.Cut(a, "=")
if name == "-modcacherw" || name == "--modcacherw" {
break
}
if len(args) == 1 && !strings.HasPrefix(a, "-") {
pkgArg = a
}
args = args[1:]
}
i++ // Does take a value; skip it.
continue
}

if bf, ok := f.Value.(interface{ IsBoolFlag() bool }); !ok || !bf.IsBoolFlag() {
// The next arg is the value for this flag. Skip it.
args = args[1:]
continue
}
}
if !strings.Contains(arg, "@") || build.IsLocalImport(arg) || filepath.IsAbs(arg) {

if !strings.Contains(pkgArg, "@") || build.IsLocalImport(pkgArg) || filepath.IsAbs(pkgArg) {
return false
}
path, version, _ := strings.Cut(arg, "@")
path, version, _ := strings.Cut(pkgArg, "@")
if path == "" || version == "" || gover.IsToolchain(path) {
return false
}

if !modcacherwSeen && base.InGOFLAGS("-modcacherw") {
fs := flag.NewFlagSet("goInstallVersion", flag.ExitOnError)
fs.Var(modcacherwVal, "modcacherw", modcacherwFlag.Usage)
base.SetFromGOFLAGS(fs)
}

// 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.
Expand Down
45 changes: 45 additions & 0 deletions src/cmd/go/testdata/script/install_modcacherw_issue64282.txt
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
# 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 relevant to downloading modules
# (currently only -modcacherw) before actually downloading the module
# to identify which toolchain version to use.
#
# 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$'
# 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
go clean -modcache


! go install -unknownflag -tags -modcacherw example.com/printversion@v0.1.0
stderr '^flag provided but not defined: -unknownflag$'
cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
go clean -modcache


# Also try it with a 'go install' that succeeds.
# (But skip in short mode, because linking a binary is expensive.)
[!short] go install -modcacherw example.com/printversion@v0.1.0
[!short] cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
[!short] go clean -modcache


# The flag should also be applied if given in GOFLAGS
# instead of on the command line.
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.

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