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// Copyright 2017 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.
// Package help implements the ``go help'' command.
package help
import (
"bufio"
"bytes"
"fmt"
"io"
"os"
"strings"
"text/template"
"unicode"
"unicode/utf8"
"cmd/go/internal/base"
)
// Help implements the 'help' command.
func Help(args []string) {
if len(args) == 0 {
PrintUsage(os.Stdout)
// not exit 2: succeeded at 'go help'.
return
}
if len(args) != 1 {
fmt.Fprintf(os.Stderr, "usage: go help command\n\nToo many arguments given.\n")
os.Exit(2) // failed at 'go help'
}
arg := args[0]
// 'go help documentation' generates doc.go.
if arg == "documentation" {
fmt.Println("// Copyright 2011 The Go Authors. All rights reserved.")
fmt.Println("// Use of this source code is governed by a BSD-style")
fmt.Println("// license that can be found in the LICENSE file.")
fmt.Println()
fmt.Println("// DO NOT EDIT THIS FILE. GENERATED BY mkalldocs.sh.")
fmt.Println("// Edit the documentation in other files and rerun mkalldocs.sh to generate this one.")
fmt.Println()
buf := new(bytes.Buffer)
PrintUsage(buf)
usage := &base.Command{Long: buf.String()}
tmpl(&commentWriter{W: os.Stdout}, documentationTemplate, append([]*base.Command{usage}, base.Commands...))
fmt.Println("package main")
return
}
for _, cmd := range base.Commands {
if cmd.Name() == arg {
tmpl(os.Stdout, helpTemplate, cmd)
// not exit 2: succeeded at 'go help cmd'.
return
}
}
fmt.Fprintf(os.Stderr, "Unknown help topic %#q. Run 'go help'.\n", arg)
os.Exit(2) // failed at 'go help cmd'
}
var usageTemplate = `Go is a tool for managing Go source code.
Usage:
go command [arguments]
The commands are:
{{range .}}{{if .Runnable}}
{{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
Use "go help [command]" for more information about a command.
Additional help topics:
{{range .}}{{if not .Runnable}}
{{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
Use "go help [topic]" for more information about that topic.
`
var helpTemplate = `{{if .Runnable}}usage: go {{.UsageLine}}
{{end}}{{.Long | trim}}
`
var documentationTemplate = `{{range .}}{{if .Short}}{{.Short | capitalize}}
{{end}}{{if .Runnable}}Usage:
go {{.UsageLine}}
{{end}}{{.Long | trim}}
{{end}}`
// commentWriter writes a Go comment to the underlying io.Writer,
// using line comment form (//).
type commentWriter struct {
W io.Writer
wroteSlashes bool // Wrote "//" at the beginning of the current line.
}
func (c *commentWriter) Write(p []byte) (int, error) {
var n int
for i, b := range p {
if !c.wroteSlashes {
s := "//"
if b != '\n' {
s = "// "
}
if _, err := io.WriteString(c.W, s); err != nil {
return n, err
}
c.wroteSlashes = true
}
n0, err := c.W.Write(p[i : i+1])
n += n0
if err != nil {
return n, err
}
if b == '\n' {
c.wroteSlashes = false
}
}
return len(p), nil
}
// An errWriter wraps a writer, recording whether a write error occurred.
type errWriter struct {
w io.Writer
err error
}
func (w *errWriter) Write(b []byte) (int, error) {
n, err := w.w.Write(b)
if err != nil {
w.err = err
}
return n, err
}
// tmpl executes the given template text on data, writing the result to w.
func tmpl(w io.Writer, text string, data interface{}) {
t := template.New("top")
t.Funcs(template.FuncMap{"trim": strings.TrimSpace, "capitalize": capitalize})
template.Must(t.Parse(text))
ew := &errWriter{w: w}
err := t.Execute(ew, data)
if ew.err != nil {
// I/O error writing. Ignore write on closed pipe.
if strings.Contains(ew.err.Error(), "pipe") {
os.Exit(1)
}
base.Fatalf("writing output: %v", ew.err)
}
if err != nil {
panic(err)
}
}
func capitalize(s string) string {
if s == "" {
return s
}
r, n := utf8.DecodeRuneInString(s)
return string(unicode.ToTitle(r)) + s[n:]
}
func PrintUsage(w io.Writer) {
bw := bufio.NewWriter(w)
tmpl(bw, usageTemplate, base.Commands)
bw.Flush()
}
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