cmd/go: split quotes in GOFLAGS same as in other env vars

GOFLAGS didn't split on quotes because no other env vars
(such as CC, CXX, ...) did either. This kept them all consistent.

CL 341936 changed everything but GOFLAGS, making them inconsistent.

Split GOFLAGS the same way as the other environment variables.

Fixes #26849.

Change-Id: I99bb450fe30cab949da48af133b6a36ff320532f
Reviewed-on: https://go-review.googlesource.com/c/go/+/443956
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Russ Cox <[email protected]>

src/cmd/go/internal/base/goflags.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 
 	"cmd/go/internal/cfg"
+	"cmd/internal/quoted"
 )
 
 var goflags []string // cached $GOFLAGS list; can be -x or --x form
@@ -30,19 +31,27 @@ func InitGOFLAGS() {
 		return
 	}
 
-	goflags = strings.Fields(cfg.Getenv("GOFLAGS"))
-	if len(goflags) == 0 {
-		// nothing to do; avoid work on later InitGOFLAGS call
-		goflags = []string{}
-		return
-	}
-
 	// Ignore bad flag in go env and go bug, because
 	// they are what people reach for when debugging
 	// a problem, and maybe they're debugging GOFLAGS.
 	// (Both will show the GOFLAGS setting if let succeed.)
 	hideErrors := cfg.CmdName == "env" || cfg.CmdName == "bug"
 
+	var err error
+	goflags, err = quoted.Split(cfg.Getenv("GOFLAGS"))
+	if err != nil {
+		if hideErrors {
+			return
+		}
+		Fatalf("go: parsing $GOFLAGS: %v", err)
+	}
+
+	if len(goflags) == 0 {
+		// nothing to do; avoid work on later InitGOFLAGS call
+		goflags = []string{}
+		return
+	}
+
 	// Each of the words returned by strings.Fields must be its own flag.
 	// To set flag arguments use -x=value instead of -x value.
 	// For boolean flags, -x is fine instead of -x=true.

src/cmd/go/internal/work/exec.go

@@ -2822,7 +2822,7 @@ func (b *Builder) gccArchArgs() []string {
 // into fields, using the default value when the variable is empty.
 //
 // The environment variable must be quoted correctly for
-// str.SplitQuotedFields. This should be done before building
+// quoted.Split. This should be done before building
 // anything, for example, in BuildInit.
 func envList(key, def string) []string {
 	v := cfg.Getenv(key)

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

@@ -55,5 +55,10 @@ go list -tags=magic
 go test -tags=magic -c -o $devnull
 go vet -tags=magic
 
+# GOFLAGS uses the same quoting rules (quoted.Split) as the rest of
+# the go command env variables
+env GOFLAGS='"-tags=magic wizardry"'
+go list
+
 -- foo_test.go --
 package foo