feat(comp): Add support for fish completion

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

cmd/helm/completion.go

@@ -52,6 +52,25 @@ To load completions for every new session, execute once:
 $ helm completion zsh > "${fpath[1]}/_helm"
 `
 
+const fishCompDesc = `
+Generate the autocompletion script for Helm for the fish shell.
+
+To load completions in your current shell session:
+$ helm completion fish | source
+
+To load completions for every new session, execute once:
+$ helm completion fish > ~/.config/fish/completions/helm.fish
+
+You will need to start a new shell for this setup to take effect.
+`
+
+const (
+	noDescFlagName = "no-descriptions"
+	noDescFlagText = "disable completion descriptions"
+)
+
+var disableCompDescriptions bool
+
 func newCompletionCmd(out io.Writer) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:               "completion",
@@ -85,7 +104,20 @@ func newCompletionCmd(out io.Writer) *cobra.Command {
 		},
 	}
 
-	cmd.AddCommand(bash, zsh)
+	fish := &cobra.Command{
+		Use:                   "fish",
+		Short:                 "generate autocompletions script for fish",
+		Long:                  fishCompDesc,
+		Args:                  require.NoArgs,
+		DisableFlagsInUseLine: true,
+		ValidArgsFunction:     noCompletions,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runCompletionFish(out, cmd)
+		},
+	}
+	fish.Flags().BoolVar(&disableCompDescriptions, noDescFlagName, false, noDescFlagText)
+
+	cmd.AddCommand(bash, zsh, fish)
 
 	return cmd
 }
@@ -257,6 +289,10 @@ __helm_bash_source <(__helm_convert_bash_to_zsh)
 	return nil
 }
 
+func runCompletionFish(out io.Writer, cmd *cobra.Command) error {
+	return cmd.Root().GenFishCompletion(out, !disableCompDescriptions)
+}
+
 // Function to disable file completion
 func noCompletions(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 	return nil, cobra.ShellCompDirectiveNoFileComp

cmd/helm/completion_test.go

@@ -55,4 +55,5 @@ func TestCompletionFileCompletion(t *testing.T) {
 	checkFileCompletion(t, "completion", false)
 	checkFileCompletion(t, "completion bash", false)
 	checkFileCompletion(t, "completion zsh", false)
+	checkFileCompletion(t, "completion fish", false)
 }