dashboard, cmd/genbootstrap: update for Go 1.21.0 and beyond

Thanks to Go 1.21.0 offering binaries for all ports at go.dev/dl/,
we won't really need genbootstrap anymore.

Update dashboard to use those binaries for GoBootstrap versions 1.21.0
and beyond, and update genbootstrap to refuse to generate bootstraps
when they aren't necessary, in case we forget and try to use it anyway.
Make an exception for Windows.

Change-Id: I75927406e44c7499b3e8a265fd58102cf3918f6f
Reviewed-on: https://go-review.googlesource.com/c/build/+/520901
Reviewed-by: Heschi Kreinick <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Run-TryBot: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: dmitshur

cmd/genbootstrap/genbootstrap.go

@@ -14,6 +14,12 @@ Usage:
 
 The argument list can be a single glob pattern (for example '*'),
 which expands to all known targets matching that pattern.
+
+Deprecated: As of Go 1.21.0, genbootstrap is superseded
+by make.bash -distpack and doesn't need to be used anymore.
+The one exception are GOOS=windows targets, since their
+go.dev/dl downloads are in .zip format but the builders
+in x/build support pushing .tar.gz format only.
 */
 package main
 
@@ -35,6 +41,7 @@ import (
 	"cloud.google.com/go/storage"
 	"golang.org/x/build/dashboard"
 	"golang.org/x/build/internal/envutil"
+	"golang.org/x/build/maintner/maintnerd/maintapi/version"
 )
 
 var skipBuild = flag.String("skip_build", "", "skip bootstrap.bash and reuse output in `dir` instead")
@@ -72,11 +79,21 @@ func main() {
 		log.Printf("expanded %s: %v", pattern, list)
 	}
 
+	var nonWindowsTargets []string
 	for _, pair := range list {
 		f := strings.Split(pair, "-")
 		if len(f) != 2 && len(f) != 3 {
 			log.Fatalf("invalid target: %q", pair)
 		}
+		if goos := f[0]; goos != "windows" {
+			nonWindowsTargets = append(nonWindowsTargets, pair)
+		}
+	}
+
+	if x, _ := version.Go1PointX(*rev); x >= 21 && len(nonWindowsTargets) > 0 {
+		log.Fatalf("genbootstrap isn't needed to build Go 1.21.0 and newer bootstrap toolchains for %v, "+
+			"they're already built with make.bash -distpack and made available at go.dev/dl for all ports "+
+			"(GOOS=windows targets are permitted; builders need .tar.gz format so go.dev/dl can't be used as is)", nonWindowsTargets)
 	}
 
 	dir, err := os.MkdirTemp("", "genbootstrap-*")

dashboard/builders.go

@@ -121,7 +121,9 @@ var slowBotAliases = map[string]string{
 var Builders = map[string]*BuildConfig{}
 
 // GoBootstrap is the bootstrap Go version.
-// Bootstrap Go builds with this name must be in the bucket,
+//
+// For bootstrap versions prior to Go 1.21.0,
+// bootstrap Go builds with this name must be in the buildlet bucket,
 // usually uploaded by 'genbootstrap -upload all'.
 const GoBootstrap = "go1.20.6"
 
@@ -699,13 +701,16 @@ type HostConfig struct {
 	HostArch string
 
 	// GoBootstrap is the version of Go to use for bootstrap.
-	// A bootstrap toolchain built with that version must be in the bucket.
 	// If unset, it is set in func init to GoBootstrap (the global constant).
 	//
 	// If GoBootstrap is set to "none", it means this buildlet is not given a new bootstrap
 	// toolchain for each build, typically because it cannot download from
 	// storage.googleapis.com.
 	//
+	// For bootstrap versions prior to Go 1.21.0,
+	// a bootstrap toolchain built with that version must be in the buildlet bucket,
+	// usually uploaded by 'genbootstrap -upload all'.
+	//
 	// (See the GoBootstrapURL method.)
 	GoBootstrap string
 
@@ -1034,8 +1039,20 @@ func (c *BuildConfig) GoBootstrapURL(e *buildenv.Environment) string {
 	if hc.GoBootstrap == "none" {
 		return ""
 	}
-	return "https://storage.googleapis.com/" + e.BuildletBucket +
-		"/gobootstrap-" + hc.HostArch + "-" + hc.GoBootstrap + ".tar.gz"
+	if x, ok := version.Go1PointX(hc.GoBootstrap); ok && x < 21 {
+		return "https://storage.googleapis.com/" + e.BuildletBucket +
+			"/gobootstrap-" + hc.HostArch + "-" + hc.GoBootstrap + ".tar.gz"
+	}
+	if c.GOOS() == "windows" {
+		// Can't use Windows downloads from go.dev/dl, they're in .zip
+		// format but the buildlet API accepts only the .tar.gz format.
+		//
+		// Since all this will be replaced by LUCI fairly soon,
+		// keep using the bootstrap bucket for Windows for now.
+		return "https://storage.googleapis.com/" + e.BuildletBucket +
+			"/gobootstrap-" + hc.HostArch + "-" + hc.GoBootstrap + ".tar.gz"
+	}
+	return "https://go.dev/dl/" + hc.GoBootstrap + "." + hc.HostArch + ".tar.gz"
 }
 
 // BuildletBinaryURL returns the public URL of this builder's buildlet.