Cleanup flag parsing.

This also changes the types flag from a single comma separated list to
a repeated flag that fills an array. This changes the name from types
to type, which is a minor breaking change.

Let me know what you think.

Author: dlorenc

cmd/analyze.go

@@ -20,7 +20,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"strings"
 
 	"github.com/GoogleCloudPlatform/container-diff/differs"
 	pkgutil "github.com/GoogleCloudPlatform/container-diff/pkg/util"
@@ -33,16 +32,13 @@ var analyzeCmd = &cobra.Command{
 	Short: "Analyzes an image: [image]",
 	Long:  `Analyzes an image using the specifed analyzers as indicated via flags (see documentation for available ones).`,
 	Args: func(cmd *cobra.Command, args []string) error {
-		if err := validateArgs(args, checkAnalyzeArgNum); err != nil {
-			return err
-		}
-		if err := checkIfValidAnalyzer(types); err != nil {
+		if err := validateArgs(args, checkAnalyzeArgNum, checkIfValidAnalyzer); err != nil {
 			return err
 		}
 		return nil
 	},
 	Run: func(cmd *cobra.Command, args []string) {
-		if err := analyzeImage(args[0], strings.Split(types, ",")); err != nil {
+		if err := analyzeImage(args[0], types); err != nil {
 			logrus.Error(err)
 			os.Exit(1)
 		}

cmd/diff.go

@@ -19,14 +19,14 @@ package cmd
 import (
 	"errors"
 	"fmt"
+	"os"
+	"sync"
+
 	"github.com/GoogleCloudPlatform/container-diff/differs"
 	pkgutil "github.com/GoogleCloudPlatform/container-diff/pkg/util"
 	"github.com/GoogleCloudPlatform/container-diff/util"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
-	"os"
-	"strings"
-	"sync"
 )
 
 var filename string
@@ -36,19 +36,13 @@ var diffCmd = &cobra.Command{
 	Short: "Compare two images: [image1] [image2]",
 	Long:  `Compares two images using the specifed analyzers as indicated via flags (see documentation for available ones).`,
 	Args: func(cmd *cobra.Command, args []string) error {
-		if err := validateArgs(args, checkDiffArgNum); err != nil {
-			return err
-		}
-		if err := checkIfValidAnalyzer(types); err != nil {
-			return err
-		}
-		if err := checkFilenameFlag(types); err != nil {
+		if err := validateArgs(args, checkDiffArgNum, checkIfValidAnalyzer, checkFilenameFlag); err != nil {
 			return err
 		}
 		return nil
 	},
 	Run: func(cmd *cobra.Command, args []string) {
-		if err := diffImages(args[0], args[1], strings.Split(types, ",")); err != nil {
+		if err := diffImages(args[0], args[1], types); err != nil {
 			logrus.Error(err)
 			os.Exit(1)
 		}
@@ -62,13 +56,16 @@ func checkDiffArgNum(args []string) error {
 	return nil
 }
 
-func checkFilenameFlag(types string) error {
-	if filename != "" {
-		if !strings.Contains(types, "file") {
-			return errors.New("Please include --types=file with the --filename flag")
+func checkFilenameFlag(_ []string) error {
+	if filename == "" {
+		return nil
+	}
+	for _, t := range types {
+		if t == "file" {
+			return nil
 		}
 	}
-	return nil
+	return errors.New("Please include --types=file with the --filename flag")
 }
 
 func diffImages(image1Arg, image2Arg string, diffArgs []string) error {

cmd/root.go

@@ -35,7 +35,7 @@ import (
 
 var json bool
 var save bool
-var types string
+var types diffTypes = []string{"apt"}
 
 var LogLevel string
 
@@ -104,12 +104,11 @@ func validateArgs(args []string, validatefxns ...validatefxn) error {
 	return nil
 }
 
-func checkIfValidAnalyzer(flagtypes string) error {
-	if flagtypes == "" {
+func checkIfValidAnalyzer(_ []string) error {
+	if len(types) == 0 {
 		return errors.New("Please provide at least one analyzer to run")
 	}
-	analyzers := strings.Split(flagtypes, ",")
-	for _, name := range analyzers {
+	for _, name := range types {
 		if _, exists := differs.Analyzers[name]; !exists {
 			return fmt.Errorf("Argument %s is not a valid analyzer", name)
 		}
@@ -146,9 +145,35 @@ func init() {
 	pflag.CommandLine.AddGoFlagSet(goflag.CommandLine)
 }
 
+// Define a type named "diffSlice" as a slice of strings
+type diffTypes []string
+
+// Now, for our new type, implement the two methods of
+// the flag.Value interface...
+// The first method is String() string
+func (d *diffTypes) String() string {
+	return strings.Join(*d, ",")
+}
+
+// The second method is Set(value string) error
+func (d *diffTypes) Set(value string) error {
+	// Dedupe repeated elements.
+	for _, t := range *d {
+		if t == value {
+			return nil
+		}
+	}
+	*d = append(*d, value)
+	return nil
+}
+
+func (d *diffTypes) Type() string {
+	return "Diff Types"
+}
+
 func addSharedFlags(cmd *cobra.Command) {
 	cmd.Flags().BoolVarP(&json, "json", "j", false, "JSON Output defines if the diff should be returned in a human readable format (false) or a JSON (true).")
-	cmd.Flags().StringVarP(&types, "types", "t", "apt", "This flag sets the list of analyzer types to use.  It expects a comma separated list of supported analyzers.")
+	cmd.Flags().VarP(&types, "type", "t", "This flag sets the list of analyzer types to use. Set it repeatedly to use multiple analyzers.")
 	cmd.Flags().BoolVarP(&save, "save", "s", false, "Set this flag to save rather than remove the final image filesystems on exit.")
 	cmd.Flags().BoolVarP(&util.SortSize, "order", "o", false, "Set this flag to sort any file/package results by descending size. Otherwise, they will be sorted by name.")
 }