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..646e4286cc8d6893bc61ffbf595ae05445d1c483
--- /dev/null
+++ b/mojom/mojom_parser/mojom_main.go
@@ -0,0 +1,132 @@
+// 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 (
+	"bytes"
+	"flag"
+	"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>]
+//
+//	where <commands> is one of:
+//		- parse
+//		- fmt
+//
+//	For further information about each command, see the file named
+//	<command>_cmd.go for example "parse_cmd.go" and "fmt_cmd.go".
+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 {
+	b := bytes.Buffer{}
+	b.WriteString(fmt.Sprintf("%s is a tool for managing .mojom files.\n\n", toolName))
+	b.WriteString("Usage:\n\n")
+	b.WriteString(fmt.Sprintf("\t%s <command> [<arguments>]\n\n", toolName))
+	b.WriteString("The commands are:\n\n")
+
+	for _, name := range c.commandNames {
+		b.WriteString(fmt.Sprintf("\t%s\t%s\n", name, c.commandMap[name].Desc))
+	}
+	return b.String()
+}
+
+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", args[1])
+		fmt.Print(c.Usage(args[0]))
+		os.Exit(1)
+	}
+
+	cmd.Func(args)
+}
+
+// GetFlagDefaults constructs a usage string for the flags of a FlagSet.
+func GetFlagDefaults(f *flag.FlagSet) string {

[rudominer, 2016/02/20 05:53:49]

Seems like a strange name for this function. How about UsageString() or
HelpString()?

[azani, 2016/02/22 17:37:39]

Done.

+	b := bytes.Buffer{}
+
+	// isZeroValue guesses if the string represents the zero value for a flag.

[rudominer, 2016/02/20 05:53:49]

explain why--how is this used?

[azani, 2016/02/22 17:37:39]

Done.

+	isZeroValue := func(value string) bool {
+		switch value {
+		case "false":
+			return true
+		case "":
+			return true
+		case "0":
+			return true
+		}
+		return false
+	}
+
+	f.VisitAll(func(f *flag.Flag) {

[rudominer, 2016/02/20 05:53:49]

Please add comment explaining what is happening here.

[azani, 2016/02/22 17:37:39]

Done.

+		s := fmt.Sprintf("  -%s", f.Name) // Two spaces before -; see next two comments.
+		// Four spaces before the tab triggers good alignment
+		// for both 4- and 8-space tab stops.
+		s += "\n    \t"
+		s += f.Usage
+		if !isZeroValue(f.DefValue) {
+			s += fmt.Sprintf(" (default %q)", f.DefValue)
+		}
+		b.WriteString(fmt.Sprint(s, "\n"))
+	})
+
+	return b.String()
+}