Mojom formatter incorporated in the mojom binary.

mojom/mojom_parser/mojom_main.go

Index: mojom/mojom_parser/mojom_main.go
diff --git a/mojom/mojom_parser/mojom_main.go b/mojom/mojom_parser/mojom_main.go
new file mode 100644
index 0000000000000000000000000000000000000000..88886377940fc06c4edf1832d9e6eed5124453ff
--- /dev/null
+++ b/mojom/mojom_parser/mojom_main.go
@@ -0,0 +1,93 @@
+// 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)
+}