Adds dynamic completions for auth contexts (#1044)

* Add dynamic completion for the `--context` flag

* Add dynamic completion to `auth` sub commands

commands/auth.go

@@ -92,16 +92,20 @@ You can provide a name to this initialization via the `+"`"+`--context`+"`"+` fl
 If the `+"`"+`--context`+"`"+` flag is not specified, a default authentication context will be created during initialization.
 
 If doctl is never initialized, you will need to specify an API token whenever you use a `+"`"+`doctl`+"`"+` command via the `+"`"+`--access-token`+"`"+` flag.`, Writer, false)
-	cmdBuilderWithInit(cmd, RunAuthSwitch, "switch", "Switches between authentication contexts", `This command allows you to switch between accounts with authentication contexts you've already created.
+	cmdAuthSwitch := cmdBuilderWithInit(cmd, RunAuthSwitch, "switch", "Switches between authentication contexts", `This command allows you to switch between accounts with authentication contexts you've already created.
 
 To see a list of available authentication contexts, call `+"`"+`doctl auth list`+"`"+`.
 
 For details on creating an authentication context, see the help for `+"`"+`doctl auth init`+"`"+`.`, Writer, false)
-	cmdBuilderWithInit(cmd, RunAuthRemove, "remove", "Remove authentication contexts ", `This command allows you to remove authentication contexts you've already created.
+	cmdAuthSwitch.AddValidArgsFunc(authContextListValidArgsFunc)
+
+	cmdAuthRemove := cmdBuilderWithInit(cmd, RunAuthRemove, "remove", "Remove authentication contexts ", `This command allows you to remove authentication contexts you've already created.
 
 To see a list of available authentication contexts, call `+"`"+`doctl auth list`+"`"+`.
 
 For details on creating an authentication context, see the help for `+"`"+`doctl auth init`+"`"+`.`, Writer, false)
+	cmdAuthRemove.AddValidArgsFunc(authContextListValidArgsFunc)
+
 	cmdAuthList := cmdBuilderWithInit(cmd, RunAuthList, "list", "List available authentication contexts", `List named authentication contexts that you created with `+"`"+`doctl auth init`+"`"+`.
 
 To switch between the contexts use `+"`"+`doctl switch <name>`+"`"+`, where `+"`"+`<name>`+"`"+` is one of the contexts listed.
@@ -272,3 +276,21 @@ func defaultConfigFileWriter() (io.WriteCloser, error) {
 
 	return f, nil
 }
+
+func getAuthContextList() []string {
+	contexts := []string{"default"}
+	cfgContexts := viper.GetStringMap("auth-contexts")
+
+	for k := range cfgContexts {
+		contexts = append(contexts, k)
+	}
+
+	return contexts
+}
+
+func authContextListValidArgsFunc(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+	if len(args) != 0 {
+		return nil, cobra.ShellCompDirectiveNoFileComp
+	}
+	return getAuthContextList(), cobra.ShellCompDirectiveNoFileComp
+}

commands/command.go

@@ -14,6 +14,7 @@ limitations under the License.
 package commands
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"strings"
@@ -46,6 +47,19 @@ func (c *Command) ChildCommands() []*Command {
 	return c.childCommands
 }
 
+type ValidArgsFunc func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective)
+
+// AddValidArgsFunc sets the function to run for dynamic completions
+// ValidArgsFunc and ValidArgs are mutually exclusive. This function will
+// return an error if ValidArgs is already set.
+func (c *Command) AddValidArgsFunc(fn ValidArgsFunc) error {
+	if len(c.Command.ValidArgs) == 0 {
+		c.Command.ValidArgsFunction = fn
+		return nil
+	}
+	return errors.New("unable to add ValidArgsFunction when ValidArgs is already set")
+}
+
 // CmdBuilder builds a new command.
 func CmdBuilder(parent *Command, cr CmdRunner, cliText, shortdesc string, longdesc string, out io.Writer, options ...cmdOption) *Command {
 	return cmdBuilderWithInit(parent, cr, cliText, shortdesc, longdesc, out, true, options...)

commands/doit.go

@@ -77,6 +77,10 @@ func init() {
 	viper.BindPFlag("output", rootPFlagSet.Lookup(doctl.ArgOutput))
 
 	rootPFlagSet.StringVarP(&Context, doctl.ArgContext, "", "", "Specify a custom authentication context name")
+	DoitCmd.RegisterFlagCompletionFunc(doctl.ArgContext, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		return getAuthContextList(), cobra.ShellCompDirectiveNoFileComp
+	})
+
 	rootPFlagSet.BoolVarP(&Trace, "trace", "", false, "Show a log of network activity while performing a command")
 	rootPFlagSet.BoolVarP(&Verbose, doctl.ArgVerbose, "v", false, "Enable verbose output")