Feature command (#12014)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

- add features command 

<!-- Issue number if applicable -->
#### Link to tracking issue
- #11998

<!--Describe what testing was performed and which tests were added.-->
#### Testing
- test with `make`
- test with `make test`
<!--Describe the documentation added.-->
#### Documentation

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Signed-off-by: danish9039 <danishsiddiqui040@gmail.com>
Co-authored-by: Alex Boten <223565+codeboten@users.noreply.github.com>

.chloggen/featuregate-command.yaml

@@ -0,0 +1,13 @@
+change_type: enhancement  
+
+component: otelcol
+
+note: "Add featuregate command to display information about available features"
+
+issues: [11998]
+
+subtext: |
+  The featuregate command allows users to view detailed information about feature gates
+  including their status, stage, and description.
+
+change_logs: [user]

otelcol/command.go

@@ -6,6 +6,9 @@ package otelcol // import "go.opentelemetry.io/collector/otelcol"
 import (
 	"errors"
 	"flag"
+	"fmt"
+	"os"
+	"text/tabwriter"
 
 	"github.com/spf13/cobra"
 
@@ -36,6 +39,7 @@ func NewCommand(set CollectorSettings) *cobra.Command {
 			return col.Run(cmd.Context())
 		},
 	}
+	rootCmd.AddCommand(newFeatureGateCommand())
 	rootCmd.AddCommand(newComponentsCommand(set))
 	rootCmd.AddCommand(newValidateSubCommand(set, flagSet))
 	rootCmd.Flags().AddGoFlagSet(flagSet)
@@ -63,3 +67,44 @@ func updateSettingsUsingFlags(set *CollectorSettings, flags *flag.FlagSet) error
 	}
 	return nil
 }
+
+func newFeatureGateCommand() *cobra.Command {
+	return &cobra.Command{
+		Use:   "featuregate [feature-id]",
+		Short: "Display feature gates information",
+		Long:  "Display information about available feature gates and their status",
+		RunE: func(_ *cobra.Command, args []string) error {
+			if len(args) > 0 {
+				found := false
+				featuregate.GlobalRegistry().VisitAll(func(g *featuregate.Gate) {
+					if g.ID() == args[0] {
+						found = true
+						fmt.Printf("Feature: %s\n", g.ID())
+						fmt.Printf("Enabled: %v\n", g.IsEnabled())
+						fmt.Printf("Stage: %s\n", g.Stage())
+						fmt.Printf("Description: %s\n", g.Description())
+						fmt.Printf("From Version: %s\n", g.FromVersion())
+						if g.ToVersion() != "" {
+							fmt.Printf("To Version: %s\n", g.ToVersion())
+						}
+					}
+				})
+				if !found {
+					return fmt.Errorf("feature %q not found", args[0])
+				}
+				return nil
+			}
+
+			w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
+			fmt.Fprintf(w, "ID\tEnabled\tStage\tDescription\n")
+			featuregate.GlobalRegistry().VisitAll(func(g *featuregate.Gate) {
+				fmt.Fprintf(w, "%s\t%v\t%s\t%s\n",
+					g.ID(),
+					g.IsEnabled(),
+					g.Stage(),
+					g.Description())
+			})
+			return w.Flush()
+		},
+	}
+}

otelcol/command_test.go

@@ -5,6 +5,8 @@ package otelcol
 
 import (
 	"context"
+	"io"
+	"os"
 	"path/filepath"
 	"testing"
 
@@ -159,3 +161,59 @@ func Test_UseUnifiedEnvVarExpansionRules(t *testing.T) {
 		})
 	}
 }
+
+func TestNewFeatureGateCommand(t *testing.T) {
+	t.Run("list all featuregates", func(t *testing.T) {
+		cmd := newFeatureGateCommand()
+		require.NotNil(t, cmd)
+
+		// Capture stdout
+		oldStdout := os.Stdout
+		r, w, _ := os.Pipe()
+		os.Stdout = w
+
+		err := cmd.RunE(cmd, []string{})
+		require.NoError(t, err)
+
+		w.Close()
+		out, _ := io.ReadAll(r)
+		os.Stdout = oldStdout
+
+		output := string(out)
+		assert.Contains(t, output, "ID")
+		assert.Contains(t, output, "Enabled")
+		assert.Contains(t, output, "Stage")
+		assert.Contains(t, output, "Description")
+	})
+	t.Run("specific featuregate details", func(t *testing.T) {
+		cmd := newFeatureGateCommand()
+
+		// Register a test feature gate in the global registry
+		featuregate.GlobalRegistry().MustRegister("test.feature", featuregate.StageBeta,
+			featuregate.WithRegisterDescription("Test feature description"))
+
+		// Capture stdout
+		oldStdout := os.Stdout
+		r, w, _ := os.Pipe()
+		os.Stdout = w
+
+		err := cmd.RunE(cmd, []string{"test.feature"})
+		require.NoError(t, err)
+
+		w.Close()
+		out, _ := io.ReadAll(r)
+		os.Stdout = oldStdout
+
+		output := string(out)
+		assert.Contains(t, output, "Feature: test.feature")
+		assert.Contains(t, output, "Description: Test feature description")
+		assert.Contains(t, output, "Stage: Beta")
+	})
+
+	t.Run("non-existent featuregate", func(t *testing.T) {
+		cmd := newFeatureGateCommand()
+		err := cmd.RunE(cmd, []string{"non.existent.feature"})
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "feature \"non.existent.feature\" not found")
+	})
+}