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 (
+        "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()
+}