Merge pull request #15 from maxmind/greg/better-help

Improve help and error output

Author: horgh

Gopkg.lock

@@ -8,6 +8,7 @@ import (
 	"os"
 
 	"github.com/mikioh/ipaddr"
+	"github.com/pkg/errors"
 )
 
 type headerFunc func([]string) []string
@@ -27,21 +28,21 @@ func ConvertFile(
 ) error {
 	outFile, err := os.Create(outputFile)
 	if err != nil {
-		return err
+		return errors.Wrapf(err, "error creating output file (%s)", outputFile)
 	}
 	defer outFile.Close()
 
 	inFile, err := os.Open(inputFile)
 	if err != nil {
-		return err
+		return errors.Wrapf(err, "error opening input file (%s)", inputFile)
 	}
 	defer inFile.Close()
 
 	return Convert(inFile, outFile, cidr, ipRange, intRange)
 }
 
 // Convert writes the MaxMind GeoIP2 or GeoLite2 CSV in the `input` io.Reader
-// to the Writer `output` using the network represenation specified by setting
+// to the Writer `output` using the network representation specified by setting
 // `cidr`, ipRange`, or `intRange` to true. If none of these are set to true,
 // it will strip off the network information.
 func Convert(
@@ -140,38 +141,41 @@ func convert(
 
 	header, err := reader.Read()
 	if err != nil {
-		return err
+		return errors.Wrap(err, "error reading CSV header")
 	}
 
 	newHeader := makeHeader(header[1:])
 	err = writer.Write(newHeader)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "error writing CSV header")
 	}
 
 	for {
 		record, err := reader.Read()
 		if err == io.EOF {
 			break
 		} else if err != nil {
-			return err
+			return errors.Wrap(err, "error reading CSV")
 		}
 
 		p, err := makePrefix(record[0])
 		if err != nil {
 			return err
 		}
-		writer.Write(makeLine(p, record[1:]))
+		err = writer.Write(makeLine(p, record[1:]))
+		if err != nil {
+			return errors.Wrap(err, "error writing CSV")
+		}
 	}
 
 	writer.Flush()
-	return writer.Error()
+	return errors.Wrap(writer.Error(), "error writing CSV")
 }
 
 func makePrefix(network string) (*ipaddr.Prefix, error) {
 	_, ipn, err := net.ParseCIDR(network)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "error parsing network (%s)", network)
 	}
 	return ipaddr.NewPrefix(ipn), nil
 }

convert/convert.go

@@ -3,38 +3,65 @@ package main
 import (
 	"flag"
 	"fmt"
+	"os"
+	"strings"
 
 	"github.com/maxmind/geoip2-csv-converter/convert"
 )
 
 func main() {
-	required := "REQUIRED"
-	input := flag.String("block-file", required, "The path to the block CSV file to use as input")
-	output := flag.String("output-file", required, "The path to the output CSV")
+	input := flag.String("block-file", "", "The path to the block CSV file to use as input (REQUIRED)")
+	output := flag.String("output-file", "", "The path to the output CSV (REQUIRED)")
 	ipRange := flag.Bool("include-range", false, "Include the IP range of the network in string format")
 	intRange := flag.Bool("include-integer-range", false, "Include the IP range of the network in integer format")
 	cidr := flag.Bool("include-cidr", false, "Include the network in CIDR format")
 
 	flag.Parse()
 
-	if *input == required || *output == required {
-		printHelp()
-		return
+	var errors []string
+
+	if *input == "" {
+		errors = append(errors, "-block-file is required")
+	}
+
+	if *output == "" {
+		errors = append(errors, "-output-file is required")
 	}
 
 	if !*ipRange && !*intRange && !*cidr {
-		printHelp()
-		return
+		errors = append(errors, "-include-cidr, -include-range, or -include-integer-range is required")
+	}
+
+	args := flag.Args()
+	if len(args) > 0 {
+		errors = append(errors, "unknown argument(s): "+strings.Join(args, ", "))
+	}
+
+	if len(errors) != 0 {
+		printHelp(errors)
+		os.Exit(1)
 	}
 
 	err := convert.ConvertFile(*input, *output, *cidr, *ipRange, *intRange)
 	if err != nil {
-		fmt.Printf("Error: %v\n", err)
+		fmt.Fprintf(flag.CommandLine.Output(), "Error: %v\n", err)
+		os.Exit(1)
 	}
 }
 
-func printHelp() {
-	flag.PrintDefaults()
-	fmt.Println("\nAt least one of -include-* param is required")
+func printHelp(errors []string) {
+	var passedFlags []string
+	flag.Visit(func(f *flag.Flag) {
+		passedFlags = append(passedFlags, "-"+f.Name)
+	})
+
+	if len(passedFlags) > 0 {
+		errors = append(errors, "flags passed: "+strings.Join(passedFlags, ", "))
+	}
+
+	for _, message := range errors {
+		fmt.Fprintln(flag.CommandLine.Output(), message)
+	}
 
+	flag.Usage()
 }