http/cgi: add Handler.Dir to specify working directory

R=golang-dev, bradfitz, alex.brainman
CC=golang-dev
https://golang.org/cl/4635042

src/pkg/http/cgi/host.go

@@ -46,6 +46,12 @@ type Handler struct {
 	Path string // path to the CGI executable
 	Root string // root URI prefix of handler or empty for "/"
 
+	// Dir specifies the CGI executable's working directory.
+	// If Dir is empty, the base directory of Path is used.
+	// If Path has no base directory, the current working
+	// directory is used.
+	Dir string
+
 	Env        []string    // extra environment variables to set, if any, as "key=value"
 	InheritEnv []string    // environment variables to inherit from host, as "key"
 	Logger     *log.Logger // optional log for errors or nil to use log.Print
@@ -125,11 +131,11 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		env = append(env, h.Env...)
 	}
 
-	path := os.Getenv("PATH")
+	envPath := os.Getenv("PATH")
-	if path == "" {
+	if envPath == "" {
-		path = "/bin:/usr/bin:/usr/ucb:/usr/bsd:/usr/local/bin"
+		envPath = "/bin:/usr/bin:/usr/ucb:/usr/bsd:/usr/local/bin"
 	}
-	env = append(env, "PATH="+path)
+	env = append(env, "PATH="+envPath)
 
 	for _, e := range h.InheritEnv {
 		if v := os.Getenv(e); v != "" {
@@ -143,7 +149,13 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		}
 	}
 
-	cwd, pathBase := filepath.Split(h.Path)
+	var cwd, path string
+	if h.Dir != "" {
+		path = h.Path
+		cwd = h.Dir
+	} else {
+		cwd, path = filepath.Split(h.Path)
+	}
 	if cwd == "" {
 		cwd = "."
 	}
@@ -154,7 +166,7 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	}
 
 	cmd := &exec.Cmd{
-		Path:   pathBase,
+		Path:   path,
 		Args:   append([]string{h.Path}, h.Args...),
 		Dir:    cwd,
 		Env:    env,

src/pkg/http/cgi/host_test.go

@@ -13,8 +13,10 @@ import (
 	"http"
 	"http/httptest"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
+	"runtime"
 )
 
 func newRequest(httpreq string) *http.Request {
@@ -301,3 +303,77 @@ func TestInternalRedirect(t *testing.T) {
 	}
 	runCgiTest(t, h, "GET /test.cgi?loc=/foo HTTP/1.0\nHost: example.com\n\n", expectedMap)
 }
+
+func TestDirUnix(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		return
+	}
+
+	cwd, _ := os.Getwd()
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+		Dir:  cwd,
+	}
+	expectedMap := map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	cwd, _ = os.Getwd()
+	cwd = filepath.Join(cwd, "testdata")
+	h = &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap = map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestDirWindows(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+
+	cgifile, _ := filepath.Abs("testdata/test.cgi")
+
+	var perl string
+	var err os.Error
+	perl, err = exec.LookPath("perl")
+	if err != nil {
+		return
+	}
+	perl, _ = filepath.Abs(perl)
+
+	cwd, _ := os.Getwd()
+	h := &Handler{
+		Path: perl,
+		Root: "/test.cgi",
+		Dir:  cwd,
+		Args: []string{cgifile},
+		Env:  []string{"SCRIPT_FILENAME=" + cgifile},
+	}
+	expectedMap := map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	// If not specify Dir on windows, working directory should be
+	// base directory of perl.
+	cwd, _ = filepath.Split(perl)
+	if cwd != "" && cwd[len(cwd)-1] == filepath.Separator {
+		cwd = cwd[:len(cwd)-1]
+	}
+	h = &Handler{
+		Path: perl,
+		Root: "/test.cgi",
+		Args: []string{cgifile},
+		Env:  []string{"SCRIPT_FILENAME=" + cgifile},
+	}
+	expectedMap = map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}

src/pkg/http/cgi/testdata/test.cgi

@@ -7,6 +7,7 @@
 
 use strict;
 use CGI;
+use Cwd;
 
 my $q = CGI->new;
 my $params = $q->Vars;
@@ -39,3 +40,16 @@ foreach my $k (sort keys %ENV) {
   $clean_env =~ s/[\n\r]//g;
   print "env-$k=$clean_env\n";
 }
+
+# NOTE: don't call getcwd() for windows.
+# msys return /c/go/src/... not C:\go\...
+my $dir;
+if ($^O eq 'MSWin32' || $^O eq 'msys') {
+  my $cmd = $ENV{'COMSPEC'} || 'c:\\windows\\system32\\cmd.exe';
+  $cmd =~ s!\\!/!g;
+  $dir = `$cmd /c cd`;
+  chomp $dir;
+} else {
+  $dir = getcwd();
+}
+print "cwd=$dir\n";