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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"
"fmt"
"io"
"os"
"strings"
"text/template"
"unicode"
"unicode/utf8"
"cmd/go/internal/base"
"cmd/internal/telemetry"
)
var counterErrorsHelpUnknownTopic = telemetry.NewCounter("go/errors:help-unknown-topic")
// Help implements the 'help' command.
func Help(w io.Writer, args []string) {
// 'go help documentation' generates doc.go.
if len(args) == 1 && args[0] == "documentation" {
fmt.Fprintln(w, "// Copyright 2011 The Go Authors. All rights reserved.")
fmt.Fprintln(w, "// Use of this source code is governed by a BSD-style")
fmt.Fprintln(w, "// license that can be found in the LICENSE file.")
fmt.Fprintln(w)
fmt.Fprintln(w, "// Code generated by 'go test cmd/go -v -run=^TestDocsUpToDate$ -fixdocs'; DO NOT EDIT.")
fmt.Fprintln(w, "// Edit the documentation in other files and then execute 'go generate cmd/go' to generate this one.")
fmt.Fprintln(w)
buf := new(strings.Builder)
PrintUsage(buf, base.Go)
usage := &base.Command{Long: buf.String()}
cmds := []*base.Command{usage}
for _, cmd := range base.Go.Commands {
cmds = append(cmds, cmd)
cmds = append(cmds, cmd.Commands...)
}
tmpl(&commentWriter{W: w}, documentationTemplate, cmds)
fmt.Fprintln(w, "package main")
return
}
cmd := base.Go
Args:
for i, arg := range args {
for _, sub := range cmd.Commands {
if sub.Name() == arg {
cmd = sub
continue Args
}
}
// helpSuccess is the help command using as many args as possible that would succeed.
helpSuccess := "go help"
if i > 0 {
helpSuccess += " " + strings.Join(args[:i], " ")
}
counterErrorsHelpUnknownTopic.Inc()
fmt.Fprintf(os.Stderr, "go help %s: unknown help topic. Run '%s'.\n", strings.Join(args, " "), helpSuccess)
base.SetExitStatus(2) // failed at 'go help cmd'
base.Exit()
}
if len(cmd.Commands) > 0 {
PrintUsage(os.Stdout, cmd)
} else {
tmpl(os.Stdout, helpTemplate, cmd)
}
// not exit 2: succeeded at 'go help cmd'.
return
}
var usageTemplate = `{{.Long | trim}}
Usage:
{{.UsageLine}} <command> [arguments]
The commands are:
{{range .Commands}}{{if or (.Runnable) .Commands}}
{{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
Use "go help{{with .LongName}} {{.}}{{end}} <command>" for more information about a command.
{{if eq (.UsageLine) "go"}}
Additional help topics:
{{range .Commands}}{{if and (not .Runnable) (not .Commands)}}
{{.Name | printf "%-15s"}} {{.Short}}{{end}}{{end}}
Use "go help{{with .LongName}} {{.}}{{end}} <topic>" for more information about that topic.
{{end}}
`
var helpTemplate = `{{if .Runnable}}usage: {{.UsageLine}}
{{end}}{{.Long | trim}}
`
var documentationTemplate = `{{range .}}{{if .Short}}{{.Short | capitalize}}
{{end}}{{if .Commands}}` + usageTemplate + `{{else}}{{if .Runnable}}Usage:
{{.UsageLine}}
{{end}}{{.Long | trim}}
{{end}}{{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 any) {
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") {
base.SetExitStatus(1)
base.Exit()
}
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, cmd *base.Command) {
bw := bufio.NewWriter(w)
tmpl(bw, usageTemplate, cmd)
bw.Flush()
}
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