feat(cli): add completion for the plugins flag

The --plugins flag now shows completion for
shows all the available plugins (external ones too!).

Author: vitorfloriano

pkg/cli/cli_test.go

@@ -231,6 +231,34 @@ var _ = Describe("CLI", func() {
 		})
 	})
 
+	Describe("completionPluginsFlag", func() {
+		It("should suggest available plugins and filter out entered/deprecated ones", func() {
+			p1 := newMockPlugin("p1.io", "v1", projectVersion)
+			p2 := newMockPlugin("p2.io", "v1", projectVersion)
+			p3 := newMockDeprecatedPlugin("p3.io", "v1-alpha", "deprecated", projectVersion)
+
+			c.plugins = makeMapFor(p1, p2, p3)
+
+			k1 := plugin.KeyFor(p1)
+			k2 := plugin.KeyFor(p2)
+
+			c.cmd = c.newRootCmd()
+			c.cmd.Flags().StringSlice(pluginsFlag, []string{}, "test usage")
+
+			err := c.cmd.Flags().Set(pluginsFlag, k1)
+			Expect(err).NotTo(HaveOccurred())
+
+			got, directive := c.completionPluginsFlag(c.cmd, []string{}, "")
+
+			Expect(directive).To(Equal(cobra.ShellCompDirectiveNoFileComp | cobra.ShellCompDirectiveNoSpace))
+
+			expected := fmt.Sprintf("%s\tExternal or custom plugin", k2)
+
+			Expect(got).To(HaveLen(1))
+			Expect(got).To(ContainElement(expected))
+		})
+	})
+
 	Context("buildCmd", func() {
 		var projectFile string
 

pkg/cli/root.go

@@ -103,6 +103,7 @@ func (c CLI) newRootCmd() *cobra.Command {
 
 	// Global flags for all subcommands.
 	cmd.PersistentFlags().StringSlice(pluginsFlag, nil, "plugin keys to be used for this subcommand execution")
+	cobra.CheckErr(cmd.RegisterFlagCompletionFunc(pluginsFlag, c.completionPluginsFlag))
 
 	// Register --project-version on the root command so that it shows up in help.
 	cmd.Flags().String(projectVersionFlag, c.defaultProjectVersion.String(), "project version")
@@ -252,3 +253,48 @@ func (c CLI) getPluginTableFilteredWithOptions(filter func(plugin.Plugin) bool,
 
 	return strings.Join(lines, "\n")
 }
+
+// completePluginsFlag implements cobra.CompletionFunc and is registered
+// as the flag completion function for --plugins
+// We should note that flag completion does not work for comma-chained values
+// but works fine when repeating the flag
+func (c CLI) completionPluginsFlag(
+	cmd *cobra.Command,
+	_ []string,
+	_ string,
+) ([]string, cobra.ShellCompDirective) {
+	// We filter strings that the user already passed to --plugins,
+	// in case the user chains the --plugins flag multiple times,
+	alreadyEntered, err := cmd.Flags().GetStringSlice(pluginsFlag)
+	if err != nil {
+		cobra.CheckErr(err)
+	}
+
+	comps := make([]string, 0, len(c.plugins))
+
+	for pluginKey, p := range c.plugins {
+		if slices.Contains(alreadyEntered, pluginKey) {
+			continue
+		}
+
+		// We also omit deprecated plugins from completion
+		if deprecated, ok := p.(plugin.Deprecated); ok {
+			if deprecated.DeprecationWarning() != "" {
+				continue
+			}
+		}
+
+		// If the plugin provides a description, we show that
+		// otherwise, we show the default description
+		desc := ""
+		if describable, ok := p.(plugin.Describable); ok {
+			desc = describable.Description()
+		} else {
+			desc = getPluginDescription(pluginKey)
+		}
+
+		comps = append(comps, cobra.CompletionWithDesc(pluginKey, desc))
+	}
+
+	return comps, cobra.ShellCompDirectiveNoFileComp | cobra.ShellCompDirectiveNoSpace
+}