go/packages: move getSizesForArgs back

..and delete go/internal/packagesdriver.

Change-Id: I2283087ae08f9e39e45aae1d51e62919c3163ce8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/592736
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

Author: adonovan

go/internal/packagesdriver/sizes.go

@@ -21,7 +21,6 @@ import (
 	"sync"
 	"unicode"
 
-	"golang.org/x/tools/go/internal/packagesdriver"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/packagesinternal"
 )
@@ -149,7 +148,7 @@ func goListDriver(cfg *Config, patterns ...string) (_ *DriverResponse, err error
 	if cfg.Mode&NeedTypesSizes != 0 || cfg.Mode&NeedTypes != 0 {
 		errCh := make(chan error)
 		go func() {
-			compiler, arch, err := packagesdriver.GetSizesForArgsGolist(ctx, state.cfgInvocation(), cfg.gocmdRunner)
+			compiler, arch, err := getSizesForArgs(ctx, state.cfgInvocation(), cfg.gocmdRunner)
 			response.dr.Compiler = compiler
 			response.dr.Arch = arch
 			errCh <- err
@@ -1024,3 +1023,44 @@ func cmdDebugStr(cmd *exec.Cmd) string {
 	}
 	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], strings.Join(args, " "))
 }
+
+// getSizesForArgs queries 'go list' for the appropriate
+// Compiler and GOARCH arguments to pass to [types.SizesFor].
+func getSizesForArgs(ctx context.Context, inv gocommand.Invocation, gocmdRunner *gocommand.Runner) (string, string, error) {
+	inv.Verb = "list"
+	inv.Args = []string{"-f", "{{context.GOARCH}} {{context.Compiler}}", "--", "unsafe"}
+	stdout, stderr, friendlyErr, rawErr := gocmdRunner.RunRaw(ctx, inv)
+	var goarch, compiler string
+	if rawErr != nil {
+		rawErrMsg := rawErr.Error()
+		if strings.Contains(rawErrMsg, "cannot find main module") ||
+			strings.Contains(rawErrMsg, "go.mod file not found") {
+			// User's running outside of a module.
+			// All bets are off. Get GOARCH and guess compiler is gc.
+			// TODO(matloob): Is this a problem in practice?
+			inv.Verb = "env"
+			inv.Args = []string{"GOARCH"}
+			envout, enverr := gocmdRunner.Run(ctx, inv)
+			if enverr != nil {
+				return "", "", enverr
+			}
+			goarch = strings.TrimSpace(envout.String())
+			compiler = "gc"
+		} else if friendlyErr != nil {
+			return "", "", friendlyErr
+		} else {
+			// This should be unreachable, but be defensive
+			// in case RunRaw's error results are inconsistent.
+			return "", "", rawErr
+		}
+	} else {
+		fields := strings.Fields(stdout.String())
+		if len(fields) < 2 {
+			return "", "", fmt.Errorf("could not parse GOARCH and Go compiler in format \"<GOARCH> <compiler>\":\nstdout: <<%s>>\nstderr: <<%s>>",
+				stdout.String(), stderr.String())
+		}
+		goarch = fields[0]
+		compiler = fields[1]
+	}
+	return compiler, goarch, nil
+}