go/packages: improve debug logging

Address a few irritating glitches in the go list debug logging.
- Print a fully runnable command line, with args like "a" "b" "c"
instead of [a b c].
- Include stderr in the debug logs for cases where the command fails.
- Print the correct PWD environment var from cmd instead of cfg.

Change-Id: I58e77b370baf8378a21377b81ee2ba5d21a557ab
Reviewed-on: https://go-review.googlesource.com/c/163497
Run-TryBot: Heschi Kreinick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: heschi

go/packages/golist.go

@@ -728,9 +728,6 @@ func golistargs(cfg *Config, words []string) []string {
 
 // invokeGo returns the stdout of a go command invocation.
 func invokeGo(cfg *Config, args ...string) (*bytes.Buffer, error) {
-	if debug {
-		defer func(start time.Time) { log.Printf("%s for %v", time.Since(start), cmdDebugStr(cfg, args...)) }(time.Now())
-	}
 	stdout := new(bytes.Buffer)
 	stderr := new(bytes.Buffer)
 	cmd := exec.CommandContext(cfg.Context, "go", args...)
@@ -744,6 +741,12 @@ func invokeGo(cfg *Config, args ...string) (*bytes.Buffer, error) {
 	cmd.Dir = cfg.Dir
 	cmd.Stdout = stdout
 	cmd.Stderr = stderr
+	if debug {
+		defer func(start time.Time) {
+			log.Printf("%s for %v, stderr: <<%s>>\n", time.Since(start), cmdDebugStr(cmd, args...), stderr)
+		}(time.Now())
+	}
+
 	if err := cmd.Run(); err != nil {
 		exitErr, ok := err.(*exec.ExitError)
 		if !ok {
@@ -777,12 +780,12 @@ func invokeGo(cfg *Config, args ...string) (*bytes.Buffer, error) {
 	// be useful for debugging. Print them if $GOPACKAGESPRINTGOLISTERRORS
 	// is set.
 	if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTGOLISTERRORS") != "" {
-		fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cfg, args...), stderr)
+		fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd, args...), stderr)
 	}
 
 	// debugging
 	if false {
-		fmt.Fprintf(os.Stderr, "%s stdout: <<%s>>\n", cmdDebugStr(cfg, args...), stdout)
+		fmt.Fprintf(os.Stderr, "%s stdout: <<%s>>\n", cmdDebugStr(cmd, args...), stdout)
 	}
 
 	return stdout, nil
@@ -797,13 +800,17 @@ func containsGoFile(s []string) bool {
 	return false
 }
 
-func cmdDebugStr(cfg *Config, args ...string) string {
+func cmdDebugStr(cmd *exec.Cmd, args ...string) string {
 	env := make(map[string]string)
-	for _, kv := range cfg.Env {
+	for _, kv := range cmd.Env {
 		split := strings.Split(kv, "=")
 		k, v := split[0], split[1]
 		env[k] = v
 	}
+	var quotedArgs []string
+	for _, arg := range args {
+		quotedArgs = append(quotedArgs, strconv.Quote(arg))
+	}
 
-	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v PWD=%v go %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["PWD"], args)
+	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v PWD=%v go %s", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["PWD"], strings.Join(quotedArgs, " "))
 }