blob: 76c7dba2d95f57a589ec708b50a463aa2683e2f7 [file] [log] [blame]
// Copyright 2015 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.
// Doc (usually run as go doc) accepts zero, one or two arguments.
//
// Zero arguments:
// go doc
// Show the documentation for the package in the current directory.
//
// One argument:
// go doc <pkg>
// go doc <sym>[.<methodOrField>]
// go doc [<pkg>.]<sym>[.<methodOrField>]
// go doc [<pkg>.][<sym>.]<methodOrField>
// The first item in this list that succeeds is the one whose documentation
// is printed. If there is a symbol but no package, the package in the current
// directory is chosen. However, if the argument begins with a capital
// letter it is always assumed to be a symbol in the current directory.
//
// Two arguments:
// go doc <pkg> <sym>[.<methodOrField>]
//
// Show the documentation for the package, symbol, and method or field. The
// first argument must be a full package path. This is similar to the
// command-line usage for the godoc command.
//
// For commands, unless the -cmd flag is present "go doc command"
// shows only the package-level docs for the package.
//
// For complete documentation, run "go help doc".
package main
import (
"bytes"
"flag"
"fmt"
"go/build"
"io"
"log"
"os"
"path/filepath"
"strings"
"unicode"
"unicode/utf8"
)
var (
unexported bool // -u flag
matchCase bool // -c flag
showCmd bool // -cmd flag
)
// usage is a replacement usage function for the flags package.
func usage() {
fmt.Fprintf(os.Stderr, "Usage of [go] doc:\n")
fmt.Fprintf(os.Stderr, "\tgo doc\n")
fmt.Fprintf(os.Stderr, "\tgo doc <pkg>\n")
fmt.Fprintf(os.Stderr, "\tgo doc <sym>[.<method>]\n")
fmt.Fprintf(os.Stderr, "\tgo doc [<pkg>].<sym>[.<method>]\n")
fmt.Fprintf(os.Stderr, "\tgo doc <pkg> <sym>[.<method>]\n")
fmt.Fprintf(os.Stderr, "For more information run\n")
fmt.Fprintf(os.Stderr, "\tgo help doc\n\n")
fmt.Fprintf(os.Stderr, "Flags:\n")
flag.PrintDefaults()
os.Exit(2)
}
func main() {
log.SetFlags(0)
log.SetPrefix("doc: ")
err := do(os.Stdout, flag.CommandLine, os.Args[1:])
if err != nil {
log.Fatal(err)
}
}
// do is the workhorse, broken out of main to make testing easier.
func do(writer io.Writer, flagSet *flag.FlagSet, args []string) (err error) {
flagSet.Usage = usage
unexported = false
matchCase = false
flagSet.BoolVar(&unexported, "u", false, "show unexported symbols as well as exported")
flagSet.BoolVar(&matchCase, "c", false, "symbol matching honors case (paths not affected)")
flagSet.BoolVar(&showCmd, "cmd", false, "show symbols with package docs even if package is a command")
flagSet.Parse(args)
var paths []string
var symbol, method string
// Loop until something is printed.
dirs.Reset()
for i := 0; ; i++ {
buildPackage, userPath, sym, more := parseArgs(flagSet.Args())
if i > 0 && !more { // Ignore the "more" bit on the first iteration.
return failMessage(paths, symbol, method)
}
symbol, method = parseSymbol(sym)
pkg := parsePackage(writer, buildPackage, userPath)
paths = append(paths, pkg.prettyPath())
defer func() {
pkg.flush()
e := recover()
if e == nil {
return
}
pkgError, ok := e.(PackageError)
if ok {
err = pkgError
return
}
panic(e)
}()
// The builtin package needs special treatment: its symbols are lower
// case but we want to see them, always.
if pkg.build.ImportPath == "builtin" {
unexported = true
}
switch {
case symbol == "":
pkg.packageDoc() // The package exists, so we got some output.
return
case method == "":
if pkg.symbolDoc(symbol) {
return
}
default:
if pkg.methodDoc(symbol, method) {
return
}
if pkg.fieldDoc(symbol, method) {
return
}
}
}
}
// failMessage creates a nicely formatted error message when there is no result to show.
func failMessage(paths []string, symbol, method string) error {
var b bytes.Buffer
if len(paths) > 1 {
b.WriteString("s")
}
b.WriteString(" ")
for i, path := range paths {
if i > 0 {
b.WriteString(", ")
}
b.WriteString(path)
}
if method == "" {
return fmt.Errorf("no symbol %s in package%s", symbol, &b)
}
return fmt.Errorf("no method or field %s.%s in package%s", symbol, method, &b)
}
// parseArgs analyzes the arguments (if any) and returns the package
// it represents, the part of the argument the user used to identify
// the path (or "" if it's the current package) and the symbol
// (possibly with a .method) within that package.
// parseSymbol is used to analyze the symbol itself.
// The boolean final argument reports whether it is possible that
// there may be more directories worth looking at. It will only
// be true if the package path is a partial match for some directory
// and there may be more matches. For example, if the argument
// is rand.Float64, we must scan both crypto/rand and math/rand
// to find the symbol, and the first call will return crypto/rand, true.
func parseArgs(args []string) (pkg *build.Package, path, symbol string, more bool) {
switch len(args) {
default:
usage()
case 0:
// Easy: current directory.
return importDir(pwd()), "", "", false
case 1:
// Done below.
case 2:
// Package must be importable.
pkg, err := build.Import(args[0], "", build.ImportComment)
if err != nil {
log.Fatalf("%s", err)
}
return pkg, args[0], args[1], false
}
// Usual case: one argument.
arg := args[0]
// If it contains slashes, it begins with a package path.
// First, is it a complete package path as it is? If so, we are done.
// This avoids confusion over package paths that have other
// package paths as their prefix.
pkg, err := build.Import(arg, "", build.ImportComment)
if err == nil {
return pkg, arg, "", false
}
// Another disambiguator: If the symbol starts with an upper
// case letter, it can only be a symbol in the current directory.
// Kills the problem caused by case-insensitive file systems
// matching an upper case name as a package name.
if isUpper(arg) {
pkg, err := build.ImportDir(".", build.ImportComment)
if err == nil {
return pkg, "", arg, false
}
}
// If it has a slash, it must be a package path but there is a symbol.
// It's the last package path we care about.
slash := strings.LastIndex(arg, "/")
// There may be periods in the package path before or after the slash
// and between a symbol and method.
// Split the string at various periods to see what we find.
// In general there may be ambiguities but this should almost always
// work.
var period int
// slash+1: if there's no slash, the value is -1 and start is 0; otherwise
// start is the byte after the slash.
for start := slash + 1; start < len(arg); start = period + 1 {
period = strings.Index(arg[start:], ".")
symbol := ""
if period < 0 {
period = len(arg)
} else {
period += start
symbol = arg[period+1:]
}
// Have we identified a package already?
pkg, err := build.Import(arg[0:period], "", build.ImportComment)
if err == nil {
return pkg, arg[0:period], symbol, false
}
// See if we have the basename or tail of a package, as in json for encoding/json
// or ivy/value for robpike.io/ivy/value.
// Launch findPackage as a goroutine so it can return multiple paths if required.
path, ok := findPackage(arg[0:period])
if ok {
return importDir(path), arg[0:period], symbol, true
}
dirs.Reset() // Next iteration of for loop must scan all the directories again.
}
// If it has a slash, we've failed.
if slash >= 0 {
log.Fatalf("no such package %s", arg[0:period])
}
// Guess it's a symbol in the current directory.
return importDir(pwd()), "", arg, false
}
// importDir is just an error-catching wrapper for build.ImportDir.
func importDir(dir string) *build.Package {
pkg, err := build.ImportDir(dir, build.ImportComment)
if err != nil {
log.Fatal(err)
}
return pkg
}
// parseSymbol breaks str apart into a symbol and method.
// Both may be missing or the method may be missing.
// If present, each must be a valid Go identifier.
func parseSymbol(str string) (symbol, method string) {
if str == "" {
return
}
elem := strings.Split(str, ".")
switch len(elem) {
case 1:
case 2:
method = elem[1]
isIdentifier(method)
default:
log.Printf("too many periods in symbol specification")
usage()
}
symbol = elem[0]
isIdentifier(symbol)
return
}
// isIdentifier checks that the name is valid Go identifier, and
// logs and exits if it is not.
func isIdentifier(name string) {
if len(name) == 0 {
log.Fatal("empty symbol")
}
for i, ch := range name {
if unicode.IsLetter(ch) || ch == '_' || i > 0 && unicode.IsDigit(ch) {
continue
}
log.Fatalf("invalid identifier %q", name)
}
}
// isExported reports whether the name is an exported identifier.
// If the unexported flag (-u) is true, isExported returns true because
// it means that we treat the name as if it is exported.
func isExported(name string) bool {
return unexported || isUpper(name)
}
// isUpper reports whether the name starts with an upper case letter.
func isUpper(name string) bool {
ch, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(ch)
}
// findPackage returns the full file name path that first matches the
// (perhaps partial) package path pkg. The boolean reports if any match was found.
func findPackage(pkg string) (string, bool) {
if pkg == "" || isUpper(pkg) { // Upper case symbol cannot be a package name.
return "", false
}
pkgString := filepath.Clean(string(filepath.Separator) + pkg)
for {
path, ok := dirs.Next()
if !ok {
return "", false
}
if strings.HasSuffix(path, pkgString) {
return path, true
}
}
}
// splitGopath splits $GOPATH into a list of roots.
func splitGopath() []string {
return filepath.SplitList(build.Default.GOPATH)
}
// pwd returns the current directory.
func pwd() string {
wd, err := os.Getwd()
if err != nil {
log.Fatal(err)
}
return wd
}