cmd/go: make env -w and -u validate GOOS and GOARCH values

This change makes go env -w and -u check invalid GOOS and GOARCH values and abort if that's the case.

Fixes #34194

Change-Id: Idca8e93bb0b190fd273bf786c925be7993c24a2b
GitHub-Last-Rev: ee67f09d75f4552001cb8b6506bc4af0894c9b05
GitHub-Pull-Request: golang/go#34221
Reviewed-on: https://go-review.googlesource.com/c/go/+/194617
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/envcmd/env.go

@@ -8,6 +8,7 @@ package envcmd
 import (
 	"encoding/json"
 	"fmt"
+	"go/build"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -249,6 +250,21 @@ func runEnv(cmd *base.Command, args []string) {
 				fmt.Fprintf(os.Stderr, "warning: go env -w %s=... does not override conflicting OS environment variable\n", key)
 			}
 		}
+
+		goos, okGOOS := add["GOOS"]
+		goarch, okGOARCH := add["GOARCH"]
+		if okGOOS || okGOARCH {
+			if !okGOOS {
+				goos = cfg.Goos
+			}
+			if !okGOARCH {
+				goarch = cfg.Goarch
+			}
+			if err := work.CheckGOOSARCHPair(goos, goarch); err != nil {
+				base.Fatalf("go env -w: %v", err)
+			}
+		}
+
 		updateEnvFile(add, nil)
 		return
 	}
@@ -265,6 +281,24 @@ func runEnv(cmd *base.Command, args []string) {
 			}
 			del[arg] = true
 		}
+		if del["GOOS"] || del["GOARCH"] {
+			goos, goarch := cfg.Goos, cfg.Goarch
+			if del["GOOS"] {
+				goos = getOrigEnv("GOOS")
+				if goos == "" {
+					goos = build.Default.GOOS
+				}
+			}
+			if del["GOARCH"] {
+				goarch = getOrigEnv("GOARCH")
+				if goarch == "" {
+					goarch = build.Default.GOARCH
+				}
+			}
+			if err := work.CheckGOOSARCHPair(goos, goarch); err != nil {
+				base.Fatalf("go env -u: %v", err)
+			}
+		}
 		updateEnvFile(nil, del)
 		return
 	}
@@ -331,6 +365,15 @@ func printEnvAsJSON(env []cfg.EnvVar) {
 	}
 }
 
+func getOrigEnv(key string) string {
+	for _, v := range cfg.OrigEnv {
+		if strings.HasPrefix(v, key+"=") {
+			return strings.TrimPrefix(v, key+"=")
+		}
+	}
+	return ""
+}
+
 func checkEnvWrite(key, val string) error {
 	switch key {
 	case "GOEXE", "GOGCCFLAGS", "GOHOSTARCH", "GOHOSTOS", "GOMOD", "GOTOOLDIR":

src/cmd/go/internal/work/action.go

@@ -290,11 +290,12 @@ func (b *Builder) Init() {
 		}
 	}
 
-	if _, ok := cfg.OSArchSupportsCgo[cfg.Goos+"/"+cfg.Goarch]; !ok && cfg.BuildContext.Compiler == "gc" {
-		fmt.Fprintf(os.Stderr, "cmd/go: unsupported GOOS/GOARCH pair %s/%s\n", cfg.Goos, cfg.Goarch)
+	if err := CheckGOOSARCHPair(cfg.Goos, cfg.Goarch); err != nil {
+		fmt.Fprintf(os.Stderr, "cmd/go: %v", err)
 		base.SetExitStatus(2)
 		base.Exit()
 	}
+
 	for _, tag := range cfg.BuildContext.BuildTags {
 		if strings.Contains(tag, ",") {
 			fmt.Fprintf(os.Stderr, "cmd/go: -tags space-separated list contains comma\n")
@@ -304,6 +305,13 @@ func (b *Builder) Init() {
 	}
 }
 
+func CheckGOOSARCHPair(goos, goarch string) error {
+	if _, ok := cfg.OSArchSupportsCgo[goos+"/"+goarch]; !ok && cfg.BuildContext.Compiler == "gc" {
+		return fmt.Errorf("unsupported GOOS/GOARCH pair %s/%s", goos, goarch)
+	}
+	return nil
+}
+
 // NewObjdir returns the name of a fresh object directory under b.WorkDir.
 // It is up to the caller to call b.Mkdir on the result at an appropriate time.
 // The result ends in a slash, so that file names in that directory

src/cmd/go/testdata/script/env_write.txt

@@ -96,3 +96,24 @@ stderr 'GOPATH entry cannot start with shell metacharacter'
 
 ! go env -w GOPATH=./go
 stderr 'GOPATH entry is relative; must be absolute path'
+
+# go env -w/-u checks validity of GOOS/ARCH combinations
+env GOOS=
+env GOARCH=
+# check -w doesn't allow invalid GOOS
+! go env -w GOOS=linuxx
+stderr 'unsupported GOOS/GOARCH pair linuxx'
+# check -w doesn't allow invalid GOARCH
+! go env -w GOARCH=amd644
+stderr 'unsupported GOOS/GOARCH.*/amd644$'
+# check -w doesn't allow invalid GOOS with valid GOARCH
+! go env -w GOOS=linuxx GOARCH=amd64
+stderr 'unsupported GOOS/GOARCH pair linuxx'
+# check a valid GOOS and GOARCH values but an incompatible combinations
+! go env -w GOOS=android GOARCH=s390x
+stderr 'unsupported GOOS/GOARCH pair android/s390x'
+# check that -u considers explicit envs
+go env -w GOOS=linux GOARCH=mips
+env GOOS=windows
+! go env -u GOOS
+stderr 'unsupported GOOS/GOARCH.*windows/mips$'