Mojom formatter incorporated in the mojom binary.

mojom/mojom_parser/mojom_main.go

+// Copyright 2015 The Chromium 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 main
+
+import (
+        "fmt"
+        "os"
+)
+
+// This file contains the main() for the mojom tool binary.
+// The mojom tool is used to process .mojom files.
+//
+// The tool is invoked as follows:
+//
+//              mojom command [arguments]

[rudominer, 2016/02/19 05:49:16]

put "command" and "arguments" in angle brackets to indicate that they are not
literals the way that "mojom" is.

 mojom <command> [<arguments>]

[azani, 2016/02/19 19:28:29]

Done.

+//
+// To see the implementation of the commands, look at parse_cmd.go and
+// fmt_cmd.go.

[rudominer, 2016/02/19 05:49:16]

Instead of this statement I would prefer a continuation of the description of
how the tool is invoked. So something like:

The tool is invoked as follows:

         mojom <command> [<arguments>]

where <command> is one of: 
 - parse
 - fmt

For for further information about each command see the file named 
<command>_command.go,  for example "parse_command.go" and "fmt_command.go".

[azani, 2016/02/19 19:28:30]

Done.

+func main() {
+        commands := NewCommandSet()
+        commands.AddCommand("parse", parseCmd, "Parses mojom files.")
+        commands.AddCommand("fmt", fmtCmd, "Formats a mojom file.")
+        commands.AddHelpCommand()
+        commands.RunCommand(os.Args)
+}
+
+func ErrorExit(message string) {
+        fmt.Fprintf(os.Stderr, "%s\n", message)
+        os.Exit(1)
+}
+
+type command struct {
+        Name string
+        Func func([]string)
+        Desc string
+}
+
+type commandSet struct {
+        commandNames []string
+        commandMap   map[string]command
+}
+
+func NewCommandSet() *commandSet {
+        commandSet := new(commandSet)
+        commandSet.commandMap = make(map[string]command)
+        return commandSet
+}
+
+func (c *commandSet) AddCommand(name string, f func([]string), desc string) {
+        if _, ok := c.commandMap[name]; ok {
+                panic(fmt.Sprintf("Tried to add a second command with the name: %s", name))
+        }
+        c.commandNames = append(c.commandNames, name)
+        c.commandMap[name] = command{name, f, desc}
+}
+
+func (c *commandSet) Usage(toolName string) string {
+        usage := "Mojom is a tool for managing .mojom files.\n\n"

[rudominer, 2016/02/19 05:49:16]

Instead of "Mojom" you should toolName here.

[azani, 2016/02/19 19:28:30]

Done.

+        usage += "Usage:\n\n"
+        usage += fmt.Sprintf("\t%s command [arguments]\n\n", toolName)

[rudominer, 2016/02/19 05:49:16]

Put angle brackets around "command" (and maybe also around "arguments"?)

[azani, 2016/02/19 19:28:30]

Done.

+        usage += "The commands are:\n\n"
+
+        for _, name := range c.commandNames {
+                usage += fmt.Sprintf("\t%s\t%s\n", name, c.commandMap[name].Desc)

[rudominer, 2016/02/19 05:49:16]

use a byte.buffer to build up the usage string. see for example what you did in
printer.go.

[azani, 2016/02/19 19:28:29]

Done.

+        }
+        return usage
+}
+
+func (c *commandSet) AddHelpCommand() {
+        helpCmd := func(args []string) {
+                fmt.Print(c.Usage(args[0]))
+        }
+        c.AddCommand("help", helpCmd, "Prints out this help message.")
+}
+
+func (c *commandSet) RunCommand(args []string) {
+        if len(args) < 2 {
+                fmt.Println("No command specified.")
+                fmt.Print(c.Usage(args[0]))
+                os.Exit(1)
+        }
+
+        cmd, ok := c.commandMap[args[1]]
+        if !ok {
+                fmt.Printf("%s is not a recognized command.\n")
+                fmt.Print(c.Usage(args[0]))
+                os.Exit(1)
+        }
+
+        cmd.Func(args)
+}