src/cmd/godoc/main.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // godoc: Go Documentation Server

 // Web server tree:
 //
 //	http://godoc/		main landing page
 //	http://godoc/doc/	serve from $GOROOT/doc - spec, mem, etc.
 //	http://godoc/src/	serve files from $GOROOT/src; .go gets pretty-printed
 //	http://godoc/cmd/	serve documentation about commands
 //	http://godoc/pkg/	serve documentation about packages
 //				(idea is if you say import "compress/zlib", you go to
 //				http://godoc/pkg/compress/zlib)
 //
 // Command-line interface:
 //
 //	godoc packagepath [name ...]
 //
 //	godoc compress/zlib
 //		- prints doc for package compress/zlib
 //	godoc crypto/block Cipher NewCMAC
 //		- prints doc for Cipher and NewCMAC in package crypto/block

 package main

 import (
 	"archive/zip"
 	"bytes"
 	"errors"
 	_ "expvar" // to serve /debug/vars
 	"flag"
 	"fmt"
 	"go/ast"
 	"go/build"
 	"io"
 	"log"
 	"net/http"
 	_ "net/http/pprof" // to serve /debug/pprof/*
 	"net/url"
 	"os"
 	pathpkg "path"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"strings"
 )

 const defaultAddr = ":6060" // default webserver address

 var (
 	// file system to serve
 	// (with e.g.: zip -r go.zip $GOROOT -i \*.go -i \*.html -i \*.css -i \*.js -i \*.txt -i \*.c -i \*.h -i \*.s -i \*.png -i \*.jpg -i \*.sh -i favicon.ico)
 	zipfile = flag.String("zip", "", "zip file providing the file system to serve; disabled if empty")

 	// file-based index
 	writeIndex = flag.Bool("write_index", false, "write index to a file; the file name must be specified with -index_files")

 	// network
 	httpAddr   = flag.String("http", "", "HTTP service address (e.g., '"+defaultAddr+"')")
 	serverAddr = flag.String("server", "", "webserver address for command line searches")

 	// layout control
 	html    = flag.Bool("html", false, "print HTML in command-line mode")
 	srcMode = flag.Bool("src", false, "print (exported) source in command-line mode")
 	urlFlag = flag.String("url", "", "print HTML for named URL")

 	// command-line searches
 	query = flag.Bool("q", false, "arguments are considered search queries")
 )

 func serveError(w http.ResponseWriter, r *http.Request, relpath string, err error) {
 	contents := applyTemplate(errorHTML, "errorHTML", err) // err may contain an absolute path!
 	w.WriteHeader(http.StatusNotFound)
 	servePage(w, relpath, "File "+relpath, "", "", contents)
 }

 func usage() {
 	fmt.Fprintf(os.Stderr,
 		"usage: godoc package [name ...]\n"+
 			"	godoc -http="+defaultAddr+"\n")
 	flag.PrintDefaults()
 	os.Exit(2)
 }

 func loggingHandler(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
 		log.Printf("%s\t%s", req.RemoteAddr, req.URL)
 		h.ServeHTTP(w, req)
 	})
 }

 func remoteSearch(query string) (res *http.Response, err error) {
 	// list of addresses to try
 	var addrs []string
 	if *serverAddr != "" {
 		// explicit server address - only try this one
 		addrs = []string{*serverAddr}
 	} else {
 		addrs = []string{
 			defaultAddr,
 			"golang.org",
 		}
 	}

 	// remote search
 	search := remoteSearchURL(query, *html)
 	for _, addr := range addrs {
 		url := "http://" + addr + search
 		res, err = http.Get(url)
 		if err == nil && res.StatusCode == http.StatusOK {
 			break
 		}
 	}

 	if err == nil && res.StatusCode != http.StatusOK {
 		err = errors.New(res.Status)
 	}

 	return
 }

 // Does s look like a regular expression?
 func isRegexp(s string) bool {
 	return strings.IndexAny(s, ".(|)*+?^$[]") >= 0
 }

 // Make a regular expression of the form
 // names[0]|names[1]|...names[len(names)-1].
 // Returns nil if the regular expression is illegal.
 func makeRx(names []string) (rx *regexp.Regexp) {
 	if len(names) > 0 {
 		s := ""
 		for i, name := range names {
 			if i > 0 {
 				s += "|"
 			}
 			if isRegexp(name) {
 				s += name
 			} else {
 				s += "^" + name + "$" // must match exactly
 			}
 		}
 		rx, _ = regexp.Compile(s) // rx is nil if there's a compilation error
 	}
 	return
 }

 func main() {
 	flag.Usage = usage
 	flag.Parse()

 	// Check usage: either server and no args, command line and args, or index creation mode
 	if (*httpAddr != "" || *urlFlag != "") != (flag.NArg() == 0) && !*writeIndex {
 		usage()
 	}

 	if *tabwidth < 0 {
 		log.Fatalf("negative tabwidth %d", *tabwidth)
 	}

 	// Determine file system to use.
 	// TODO(gri) - fs and fsHttp should really be the same. Try to unify.
 	//           - fsHttp doesn't need to be set up in command-line mode,
 	//             same is true for the http handlers in initHandlers.
 	if *zipfile == "" {
 		// use file system of underlying OS
 		fs.Bind("/", OS(*goroot), "/", bindReplace)
 		if *templateDir != "" {
 			fs.Bind("/lib/godoc", OS(*templateDir), "/", bindBefore)
 		}
 	} else {
 		// use file system specified via .zip file (path separator must be '/')
 		rc, err := zip.OpenReader(*zipfile)
 		if err != nil {
 			log.Fatalf("%s: %s\n", *zipfile, err)
 		}
 		defer rc.Close() // be nice (e.g., -writeIndex mode)
 		fs.Bind("/", NewZipFS(rc, *zipfile), *goroot, bindReplace)
 	}

 	// Bind $GOPATH trees into Go root.
 	for _, p := range filepath.SplitList(build.Default.GOPATH) {
 		fs.Bind("/src/pkg", OS(p), "/src", bindAfter)
 	}

 	readTemplates()
 	initHandlers()

 	if *writeIndex {
 		// Write search index and exit.
 		if *indexFiles == "" {
 			log.Fatal("no index file specified")
 		}

 		log.Println("initialize file systems")
 		*verbose = true // want to see what happens
 		initFSTree()

 		*indexThrottle = 1
 		updateIndex()

 		log.Println("writing index file", *indexFiles)
 		f, err := os.Create(*indexFiles)
 		if err != nil {
 			log.Fatal(err)
 		}
 		index, _ := searchIndex.get()
 		err = index.(*Index).Write(f)
 		if err != nil {
 			log.Fatal(err)
 		}

 		log.Println("done")
 		return
 	}

 	// Print content that would be served at the URL *urlFlag.
 	if *urlFlag != "" {
 		registerPublicHandlers(http.DefaultServeMux)
 		// Try up to 10 fetches, following redirects.
 		urlstr := *urlFlag
 		for i := 0; i < 10; i++ {
 			// Prepare request.
 			u, err := url.Parse(urlstr)
 			if err != nil {
 				log.Fatal(err)
 			}
 			req := &http.Request{
 				URL: u,
 			}

 			// Invoke default HTTP handler to serve request
 			// to our buffering httpWriter.
 			w := &httpWriter{h: http.Header{}, code: 200}
 			http.DefaultServeMux.ServeHTTP(w, req)

 			// Return data, error, or follow redirect.
 			switch w.code {
 			case 200: // ok
 				os.Stdout.Write(w.Bytes())
 				return
 			case 301, 302, 303, 307: // redirect
 				redirect := w.h.Get("Location")
 				if redirect == "" {
 					log.Fatalf("HTTP %d without Location header", w.code)
 				}
 				urlstr = redirect
 			default:
 				log.Fatalf("HTTP error %d", w.code)
 			}
 		}
 		log.Fatalf("too many redirects")
 	}

 	if *httpAddr != "" {
 		// HTTP server mode.
 		var handler http.Handler = http.DefaultServeMux
 		if *verbose {
 			log.Printf("Go Documentation Server")
 			log.Printf("version = %s", runtime.Version())
 			log.Printf("address = %s", *httpAddr)
 			log.Printf("goroot = %s", *goroot)
 			log.Printf("tabwidth = %d", *tabwidth)
 			switch {
 			case !*indexEnabled:
 				log.Print("search index disabled")
 			case *maxResults > 0:
 				log.Printf("full text index enabled (maxresults = %d)", *maxResults)
 			default:
 				log.Print("identifier search index enabled")
 			}
 			fs.Fprint(os.Stderr)
 			handler = loggingHandler(handler)
 		}

 		registerPublicHandlers(http.DefaultServeMux)

 		// Playground handlers are not available in local godoc.
 		http.HandleFunc("/compile", disabledHandler)
 		http.HandleFunc("/share", disabledHandler)

 		// Initialize default directory tree with corresponding timestamp.
 		// (Do it in a goroutine so that launch is quick.)
 		go initFSTree()

 		// Immediately update metadata.
 		updateMetadata()
 		// Periodically refresh metadata.
 		go refreshMetadataLoop()

 		// Initialize search index.
 		if *indexEnabled {
 			go indexer()
 		}

 		// Start http server.
 		if err := http.ListenAndServe(*httpAddr, handler); err != nil {
 			log.Fatalf("ListenAndServe %s: %v", *httpAddr, err)
 		}

 		return
 	}

 	// Command line mode.
 	if *html {
 		packageText = packageHTML
 		searchText = packageHTML
 	}

 	if *query {
 		// Command-line queries.
 		for i := 0; i < flag.NArg(); i++ {
 			res, err := remoteSearch(flag.Arg(i))
 			if err != nil {
 				log.Fatalf("remoteSearch: %s", err)
 			}
 			io.Copy(os.Stdout, res.Body)
 		}
 		return
 	}

 	// Determine paths.
 	//
 	// If we are passed an operating system path like . or ./foo or /foo/bar or c:\mysrc,
 	// we need to map that path somewhere in the fs name space so that routines
 	// like getPageInfo will see it.  We use the arbitrarily-chosen virtual path "/target"
 	// for this.  That is, if we get passed a directory like the above, we map that
 	// directory so that getPageInfo sees it as /target.
 	const target = "/target"
 	const cmdPrefix = "cmd/"
 	path := flag.Arg(0)
 	var forceCmd bool
 	var abspath, relpath string
 	if filepath.IsAbs(path) {
 		fs.Bind(target, OS(path), "/", bindReplace)
 		abspath = target
 	} else if build.IsLocalImport(path) {
 		cwd, _ := os.Getwd() // ignore errors
 		path = filepath.Join(cwd, path)
 		fs.Bind(target, OS(path), "/", bindReplace)
 		abspath = target
 	} else if strings.HasPrefix(path, cmdPrefix) {
 		path = path[len(cmdPrefix):]
 		forceCmd = true
 	} else if bp, _ := build.Import(path, "", build.FindOnly); bp.Dir != "" && bp.ImportPath != "" {
 		fs.Bind(target, OS(bp.Dir), "/", bindReplace)
 		abspath = target
 		relpath = bp.ImportPath
 	} else {
 		abspath = pathpkg.Join(pkgHandler.fsRoot, path)
 	}
 	if relpath == "" {
 		relpath = abspath
 	}

 	var mode PageInfoMode
 	if relpath == builtinPkgPath {
 		// the fake built-in package contains unexported identifiers
 		mode = noFiltering
 	}
 	if *srcMode {
 		// only filter exports if we don't have explicit command-line filter arguments
 		if flag.NArg() > 1 {
 			mode |= noFiltering
 		}
 		mode |= showSource
 	}
 	// TODO(gri): Provide a mechanism (flag?) to select a package
 	//            if there are multiple packages in a directory.

 	// first, try as package unless forced as command
 	var info PageInfo
 	if !forceCmd {
 		info = pkgHandler.getPageInfo(abspath, relpath, "", mode)
 	}

 	// second, try as command unless the path is absolute
 	// (the go command invokes godoc w/ absolute paths; don't override)
 	var cinfo PageInfo
 	if !filepath.IsAbs(path) {
 		abspath = pathpkg.Join(cmdHandler.fsRoot, path)
 		cinfo = cmdHandler.getPageInfo(abspath, relpath, "", mode)
 	}

 	// determine what to use
 	if info.IsEmpty() {
 		if !cinfo.IsEmpty() {
 			// only cinfo exists - switch to cinfo
 			info = cinfo
 		}
 	} else if !cinfo.IsEmpty() {
 		// both info and cinfo exist - use cinfo if info
 		// contains only subdirectory information
 		if info.PAst == nil && info.PDoc == nil {
 			info = cinfo
 		} else {
 			fmt.Printf("use 'godoc %s%s' for documentation on the %s command \n\n", cmdPrefix, relpath, relpath)
 		}
 	}

 	if info.Err != nil {
 		log.Fatalf("%v", info.Err)
 	}
 	if info.PDoc != nil && info.PDoc.ImportPath == target {
 		// Replace virtual /target with actual argument from command line.
 		info.PDoc.ImportPath = flag.Arg(0)
 	}

 	// If we have more than one argument, use the remaining arguments for filtering
 	if flag.NArg() > 1 {
 		args := flag.Args()[1:]
 		rx := makeRx(args)
 		if rx == nil {
 			log.Fatalf("illegal regular expression from %v", args)
 		}

 		filter := func(s string) bool { return rx.MatchString(s) }
 		switch {
 		case info.PAst != nil:
 			ast.FilterFile(info.PAst, filter)
 			// Special case: Don't use templates for printing
 			// so we only get the filtered declarations without
 			// package clause or extra whitespace.
 			for i, d := range info.PAst.Decls {
 				if i > 0 {
 					fmt.Println()
 				}
 				if *html {
 					var buf bytes.Buffer
 					writeNode(&buf, info.FSet, d)
 					FormatText(os.Stdout, buf.Bytes(), -1, true, "", nil)
 				} else {
 					writeNode(os.Stdout, info.FSet, d)
 				}
 				fmt.Println()
 			}
 			return

 		case info.PDoc != nil:
 			info.PDoc.Filter(filter)
 		}
 	}

 	if err := packageText.Execute(os.Stdout, info); err != nil {
 		log.Printf("packageText.Execute: %s", err)
 	}
 }

 // An httpWriter is an http.ResponseWriter writing to a bytes.Buffer.
 type httpWriter struct {
 	bytes.Buffer
 	h    http.Header
 	code int
 }

 func (w *httpWriter) Header() http.Header  { return w.h }
 func (w *httpWriter) WriteHeader(code int) { w.code = code }

 // disabledHandler serves a 501 "Not Implemented" response.
 func disabledHandler(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusNotImplemented)
 	fmt.Fprint(w, "This functionality is not available via local godoc.")
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// godoc: Go Documentation Server

	// Web server tree:
	//
	// http://godoc/ main landing page
	// http://godoc/doc/ serve from $GOROOT/doc - spec, mem, etc.
	// http://godoc/src/ serve files from $GOROOT/src; .go gets pretty-printed
	// http://godoc/cmd/ serve documentation about commands
	// http://godoc/pkg/ serve documentation about packages
	// (idea is if you say import "compress/zlib", you go to
	// http://godoc/pkg/compress/zlib)
	//
	// Command-line interface:
	//
	// godoc packagepath [name ...]
	//
	// godoc compress/zlib
	// - prints doc for package compress/zlib
	// godoc crypto/block Cipher NewCMAC
	// - prints doc for Cipher and NewCMAC in package crypto/block

	package main

	import (
	"archive/zip"
	"bytes"
	"errors"
	_ "expvar" // to serve /debug/vars
	"flag"
	"fmt"
	"go/ast"
	"go/build"
	"io"
	"log"
	"net/http"
	_ "net/http/pprof" // to serve /debug/pprof/*
	"net/url"
	"os"
	pathpkg "path"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	)

	const defaultAddr = ":6060" // default webserver address

	var (
	// file system to serve
	// (with e.g.: zip -r go.zip $GOROOT -i \.go -i \.html -i \.css -i \.js -i \.txt -i \.c -i \.h -i \.s -i \.png -i \.jpg -i \*.sh -i favicon.ico)
	zipfile = flag.String("zip", "", "zip file providing the file system to serve; disabled if empty")

	// file-based index
	writeIndex = flag.Bool("write_index", false, "write index to a file; the file name must be specified with -index_files")

	// network
	httpAddr = flag.String("http", "", "HTTP service address (e.g., '"+defaultAddr+"')")
	serverAddr = flag.String("server", "", "webserver address for command line searches")

	// layout control
	html = flag.Bool("html", false, "print HTML in command-line mode")
	srcMode = flag.Bool("src", false, "print (exported) source in command-line mode")
	urlFlag = flag.String("url", "", "print HTML for named URL")

	// command-line searches
	query = flag.Bool("q", false, "arguments are considered search queries")
	)

	func serveError(w http.ResponseWriter, r *http.Request, relpath string, err error) {
	contents := applyTemplate(errorHTML, "errorHTML", err) // err may contain an absolute path!
	w.WriteHeader(http.StatusNotFound)
	servePage(w, relpath, "File "+relpath, "", "", contents)
	}

	func usage() {
	fmt.Fprintf(os.Stderr,
	"usage: godoc package [name ...]\n"+
	" godoc -http="+defaultAddr+"\n")
	flag.PrintDefaults()
	os.Exit(2)
	}

	func loggingHandler(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
	log.Printf("%s\t%s", req.RemoteAddr, req.URL)
	h.ServeHTTP(w, req)
	})
	}

	func remoteSearch(query string) (res *http.Response, err error) {
	// list of addresses to try
	var addrs []string
	if *serverAddr != "" {
	// explicit server address - only try this one
	addrs = []string{*serverAddr}
	} else {
	addrs = []string{
	defaultAddr,
	"golang.org",
	}
	}

	// remote search
	search := remoteSearchURL(query, *html)
	for _, addr := range addrs {
	url := "http://" + addr + search
	res, err = http.Get(url)
	if err == nil && res.StatusCode == http.StatusOK {
	break
	}
	}

	if err == nil && res.StatusCode != http.StatusOK {
	err = errors.New(res.Status)
	}

	return
	}

	// Does s look like a regular expression?
	func isRegexp(s string) bool {
	return strings.IndexAny(s, ".(\|)*+?^$[]") >= 0
	}

	// Make a regular expression of the form
	// names[0]\|names[1]\|...names[len(names)-1].
	// Returns nil if the regular expression is illegal.
	func makeRx(names []string) (rx *regexp.Regexp) {
	if len(names) > 0 {
	s := ""
	for i, name := range names {
	if i > 0 {
	s += "\|"
	}
	if isRegexp(name) {
	s += name
	} else {
	s += "^" + name + "$" // must match exactly
	}
	}
	rx, _ = regexp.Compile(s) // rx is nil if there's a compilation error
	}
	return
	}

	func main() {
	flag.Usage = usage
	flag.Parse()

	// Check usage: either server and no args, command line and args, or index creation mode
	if (httpAddr != "" \|\| urlFlag != "") != (flag.NArg() == 0) && !*writeIndex {
	usage()
	}

	if *tabwidth < 0 {
	log.Fatalf("negative tabwidth %d", *tabwidth)
	}

	// Determine file system to use.
	// TODO(gri) - fs and fsHttp should really be the same. Try to unify.
	// - fsHttp doesn't need to be set up in command-line mode,
	// same is true for the http handlers in initHandlers.
	if *zipfile == "" {
	// use file system of underlying OS
	fs.Bind("/", OS(*goroot), "/", bindReplace)
	if *templateDir != "" {
	fs.Bind("/lib/godoc", OS(*templateDir), "/", bindBefore)
	}
	} else {
	// use file system specified via .zip file (path separator must be '/')
	rc, err := zip.OpenReader(*zipfile)
	if err != nil {
	log.Fatalf("%s: %s\n", *zipfile, err)
	}
	defer rc.Close() // be nice (e.g., -writeIndex mode)
	fs.Bind("/", NewZipFS(rc, zipfile), goroot, bindReplace)
	}

	// Bind $GOPATH trees into Go root.
	for _, p := range filepath.SplitList(build.Default.GOPATH) {
	fs.Bind("/src/pkg", OS(p), "/src", bindAfter)
	}

	readTemplates()
	initHandlers()

	if *writeIndex {
	// Write search index and exit.
	if *indexFiles == "" {
	log.Fatal("no index file specified")
	}

	log.Println("initialize file systems")
	*verbose = true // want to see what happens
	initFSTree()

	*indexThrottle = 1
	updateIndex()

	log.Println("writing index file", *indexFiles)
	f, err := os.Create(*indexFiles)
	if err != nil {
	log.Fatal(err)
	}
	index, _ := searchIndex.get()
	err = index.(*Index).Write(f)
	if err != nil {
	log.Fatal(err)
	}

	log.Println("done")
	return
	}

	// Print content that would be served at the URL *urlFlag.
	if *urlFlag != "" {
	registerPublicHandlers(http.DefaultServeMux)
	// Try up to 10 fetches, following redirects.
	urlstr := *urlFlag
	for i := 0; i < 10; i++ {
	// Prepare request.
	u, err := url.Parse(urlstr)
	if err != nil {
	log.Fatal(err)
	}
	req := &http.Request{
	URL: u,
	}

	// Invoke default HTTP handler to serve request
	// to our buffering httpWriter.
	w := &httpWriter{h: http.Header{}, code: 200}
	http.DefaultServeMux.ServeHTTP(w, req)

	// Return data, error, or follow redirect.
	switch w.code {
	case 200: // ok
	os.Stdout.Write(w.Bytes())
	return
	case 301, 302, 303, 307: // redirect
	redirect := w.h.Get("Location")
	if redirect == "" {
	log.Fatalf("HTTP %d without Location header", w.code)
	}
	urlstr = redirect
	default:
	log.Fatalf("HTTP error %d", w.code)
	}
	}
	log.Fatalf("too many redirects")
	}

	if *httpAddr != "" {
	// HTTP server mode.
	var handler http.Handler = http.DefaultServeMux
	if *verbose {
	log.Printf("Go Documentation Server")
	log.Printf("version = %s", runtime.Version())
	log.Printf("address = %s", *httpAddr)
	log.Printf("goroot = %s", *goroot)
	log.Printf("tabwidth = %d", *tabwidth)
	switch {
	case !*indexEnabled:
	log.Print("search index disabled")
	case *maxResults > 0:
	log.Printf("full text index enabled (maxresults = %d)", *maxResults)
	default:
	log.Print("identifier search index enabled")
	}
	fs.Fprint(os.Stderr)
	handler = loggingHandler(handler)
	}

	registerPublicHandlers(http.DefaultServeMux)

	// Playground handlers are not available in local godoc.
	http.HandleFunc("/compile", disabledHandler)
	http.HandleFunc("/share", disabledHandler)

	// Initialize default directory tree with corresponding timestamp.
	// (Do it in a goroutine so that launch is quick.)
	go initFSTree()

	// Immediately update metadata.
	updateMetadata()
	// Periodically refresh metadata.
	go refreshMetadataLoop()

	// Initialize search index.
	if *indexEnabled {
	go indexer()
	}

	// Start http server.
	if err := http.ListenAndServe(*httpAddr, handler); err != nil {
	log.Fatalf("ListenAndServe %s: %v", *httpAddr, err)
	}

	return
	}

	// Command line mode.
	if *html {
	packageText = packageHTML
	searchText = packageHTML
	}

	if *query {
	// Command-line queries.
	for i := 0; i < flag.NArg(); i++ {
	res, err := remoteSearch(flag.Arg(i))
	if err != nil {
	log.Fatalf("remoteSearch: %s", err)
	}
	io.Copy(os.Stdout, res.Body)
	}
	return
	}

	// Determine paths.
	//
	// If we are passed an operating system path like . or ./foo or /foo/bar or c:\mysrc,
	// we need to map that path somewhere in the fs name space so that routines
	// like getPageInfo will see it. We use the arbitrarily-chosen virtual path "/target"
	// for this. That is, if we get passed a directory like the above, we map that
	// directory so that getPageInfo sees it as /target.
	const target = "/target"
	const cmdPrefix = "cmd/"
	path := flag.Arg(0)
	var forceCmd bool
	var abspath, relpath string
	if filepath.IsAbs(path) {
	fs.Bind(target, OS(path), "/", bindReplace)
	abspath = target
	} else if build.IsLocalImport(path) {
	cwd, _ := os.Getwd() // ignore errors
	path = filepath.Join(cwd, path)
	fs.Bind(target, OS(path), "/", bindReplace)
	abspath = target
	} else if strings.HasPrefix(path, cmdPrefix) {
	path = path[len(cmdPrefix):]
	forceCmd = true
	} else if bp, _ := build.Import(path, "", build.FindOnly); bp.Dir != "" && bp.ImportPath != "" {
	fs.Bind(target, OS(bp.Dir), "/", bindReplace)
	abspath = target
	relpath = bp.ImportPath
	} else {
	abspath = pathpkg.Join(pkgHandler.fsRoot, path)
	}
	if relpath == "" {
	relpath = abspath
	}

	var mode PageInfoMode
	if relpath == builtinPkgPath {
	// the fake built-in package contains unexported identifiers
	mode = noFiltering
	}
	if *srcMode {
	// only filter exports if we don't have explicit command-line filter arguments
	if flag.NArg() > 1 {
	mode \|= noFiltering
	}
	mode \|= showSource
	}
	// TODO(gri): Provide a mechanism (flag?) to select a package
	// if there are multiple packages in a directory.

	// first, try as package unless forced as command
	var info PageInfo
	if !forceCmd {
	info = pkgHandler.getPageInfo(abspath, relpath, "", mode)
	}

	// second, try as command unless the path is absolute
	// (the go command invokes godoc w/ absolute paths; don't override)
	var cinfo PageInfo
	if !filepath.IsAbs(path) {
	abspath = pathpkg.Join(cmdHandler.fsRoot, path)
	cinfo = cmdHandler.getPageInfo(abspath, relpath, "", mode)
	}

	// determine what to use
	if info.IsEmpty() {
	if !cinfo.IsEmpty() {
	// only cinfo exists - switch to cinfo
	info = cinfo
	}
	} else if !cinfo.IsEmpty() {
	// both info and cinfo exist - use cinfo if info
	// contains only subdirectory information
	if info.PAst == nil && info.PDoc == nil {
	info = cinfo
	} else {
	fmt.Printf("use 'godoc %s%s' for documentation on the %s command \n\n", cmdPrefix, relpath, relpath)
	}
	}

	if info.Err != nil {
	log.Fatalf("%v", info.Err)
	}
	if info.PDoc != nil && info.PDoc.ImportPath == target {
	// Replace virtual /target with actual argument from command line.
	info.PDoc.ImportPath = flag.Arg(0)
	}

	// If we have more than one argument, use the remaining arguments for filtering
	if flag.NArg() > 1 {
	args := flag.Args()[1:]
	rx := makeRx(args)
	if rx == nil {
	log.Fatalf("illegal regular expression from %v", args)
	}

	filter := func(s string) bool { return rx.MatchString(s) }
	switch {
	case info.PAst != nil:
	ast.FilterFile(info.PAst, filter)
	// Special case: Don't use templates for printing
	// so we only get the filtered declarations without
	// package clause or extra whitespace.
	for i, d := range info.PAst.Decls {
	if i > 0 {
	fmt.Println()
	}
	if *html {
	var buf bytes.Buffer
	writeNode(&buf, info.FSet, d)
	FormatText(os.Stdout, buf.Bytes(), -1, true, "", nil)
	} else {
	writeNode(os.Stdout, info.FSet, d)
	}
	fmt.Println()
	}
	return

	case info.PDoc != nil:
	info.PDoc.Filter(filter)
	}
	}

	if err := packageText.Execute(os.Stdout, info); err != nil {
	log.Printf("packageText.Execute: %s", err)
	}
	}

	// An httpWriter is an http.ResponseWriter writing to a bytes.Buffer.
	type httpWriter struct {
	bytes.Buffer
	h http.Header
	code int
	}

	func (w *httpWriter) Header() http.Header { return w.h }
	func (w *httpWriter) WriteHeader(code int) { w.code = code }

	// disabledHandler serves a 501 "Not Implemented" response.
	func disabledHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusNotImplemented)
	fmt.Fprint(w, "This functionality is not available via local godoc.")
	}