Tom Limoncelli
5 years ago
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Migration Guide: v1 to v2
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===
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<!-- toc -->
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* [Flags before args](#flags-before-args)
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* [Import string changed](#import-string-changed)
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* [Flag aliases are done differently.](#flag-aliases-are-done-differently)
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* [Commands are now lists of pointers](#commands-are-now-lists-of-pointers)
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* [Lists of commands should be pointers](#lists-of-commands-should-be-pointers)
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* [cli.Flag changed](#cliflag-changed)
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* [Appending Commands](#appending-commands)
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* [Actions returns errors](#actions-returns-errors)
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* [Everything else](#everything-else)
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* [Full API Example](#full-api-example)
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<!-- tocstop -->
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v2 has a number of breaking changes but converting is relatively
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straightforward: make the changes documented below then resolve any
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compiler errors. We hope this will be sufficient for most typical
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users.
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If you find any issues not covered by this document, please post a
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comment on [Issue 921](https://github.com/urfave/cli/issues/921) or
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consider sending a PR to help improve this guide.
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# Flags before args
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In v2 flags must come before args. This is more POSIX-compliant. You
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may need to update scripts, user documentation, etc.
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This will work:
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```
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cli hello --shout rick
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```
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This will not:
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```
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cli hello rick --shout
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```
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# Import string changed
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* OLD: `import "github.com/urfave/cli"`
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* NEW: `import "github.com/urfave/cli/v2"`
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Check each file for this and make the change.
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Shell command to find them all: `fgrep -rl github.com/urfave/cli *`
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# Flag aliases are done differently.
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Change `Name: "foo, f"` to `Name: "foo", Aliases: []string{"f"}`
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* OLD:
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```go
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cli.StringFlag{
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Name: "config, cfg"
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}
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```
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* NEW:
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```go
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cli.StringFlag{
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Name: "config",
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Aliases: []string{"cfg"},
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}
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```
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Sadly v2 doesn't warn you if a comma is in the name.
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# Commands are now lists of pointers
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Occurrences of `[]Command` have been changed to `[]*Command`.
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What this means to you:
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Look for `[]cli.Command{}` and change it to `[]*cli.Command{}`
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Example:
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* OLD: `var commands = []cli.Command{}`
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* NEW: `var commands = []*cli.Command{}`
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Compiler messages you might see:
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```
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cannot convert commands (type []cli.Command) to type cli.CommandsByName
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cannot use commands (type []cli.Command) as type []*cli.Command in assignment
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```
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# Lists of commands should be pointers
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If you are building up a list of commands, the individual items should
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now be pointers.
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* OLD: `cli.Command{`
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* NEW: `&cli.Command{`
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Compiler messages you might see:
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```
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cannot use cli.Command literal (type cli.Command) as type *cli.Command in argument to
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```
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# cli.Flag changed
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`cli.Flag` is now a list of pointers.
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What this means to you:
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If you make a list of flags, add a `&` in front of each
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item. cli.BoolFlag, cli.StringFlag, etc.
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* OLD:
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```go
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app.Flags = []cli.Flag{
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cli.BoolFlag{
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```
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* NEW:
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```go
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app.Flags = []cli.Flag{
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&cli.BoolFlag{
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```
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Compiler messages you might see:
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```
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cli.StringFlag does not implement cli.Flag (Apply method has pointer receiver)
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```
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# Appending Commands
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Appending to a list of commands needs to be changed since the list is
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now pointers.
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* OLD: `commands = append(commands, *c)`
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* NEW: `commands = append(commands, c)`
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Compiler messages you might see:
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```
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cannot use c (type *cli.Command) as type cli.Command in append
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```
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# Actions returns errors
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A command's `Action:` now returns an `error`.
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* OLD: `Action: func(c *cli.Context) {`
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* NEW: `Action: func(c *cli.Context) error {`
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Compiler messages you might see:
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```
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cannot use func literal (type func(*cli.Context)) as type cli.ActionFunc in field value
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```
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# Everything else
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Compile the code and work through any errors. Most should
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relate to issues listed above.
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Once it compiles, test the command. Review the output of `-h` or any
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help messages to verify they match the intended flags and subcommands.
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Then test the program itself.
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If you find any issues not covered by this document please let us know
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by submitting a comment on
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[Issue 921](https://github.com/urfave/cli/issues/921)
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so that others can benefit.
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