Flag help improvements (#78)

* add single flag help

* add search option, usage: --help search

* remove flag search

* add examples

* minor linting improvements

Co-authored-by: mzack <marco.rivoli.nvh@gmail.com>

examples/basic/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"log"
+
+	"github.com/projectdiscovery/goflags"
+)
+
+type Options struct {
+	name    string
+	Email   goflags.StringSlice
+	Phone   string
+	Address goflags.StringSlice
+}
+
+func main() {
+	testOptions := &Options{}
+	flagSet := goflags.NewFlagSet()
+	flagSet.CreateGroup("info", "Info",
+		flagSet.StringVarP(&testOptions.name, "name", "n", "", "name of the user"),
+		flagSet.StringSliceVarP(&testOptions.Email, "email", "e", nil, "email of the user", goflags.CommaSeparatedStringSliceOptions),
+	)
+	flagSet.CreateGroup("additional", "Additional",
+		flagSet.StringVarP(&testOptions.Phone, "phone", "ph", "", "phone of the user"),
+		flagSet.StringSliceVarP(&testOptions.Address, "address", "add", nil, "address of the user", goflags.StringSliceOptions),
+	)
+
+	if err := flagSet.Parse(); err != nil {
+		log.Fatal(err)
+	}
+}

goflags.go

@@ -5,7 +5,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -106,7 +105,7 @@ func (flagSet *FlagSet) Parse() error {
 	_ = os.MkdirAll(filepath.Dir(configFilePath), os.ModePerm)
 	if !fileutil.FileExists(configFilePath) {
 		configData := flagSet.generateDefaultConfig()
-		return ioutil.WriteFile(configFilePath, configData, os.ModePerm)
+		return os.WriteFile(configFilePath, configData, os.ModePerm)
 	}
 	_ = flagSet.MergeConfigFile(configFilePath) // try to read default config after parsing flags
 	return nil
@@ -530,6 +529,11 @@ func (flagSet *FlagSet) usageFunc() {
 			flagSet.displayGroupUsageFunc(newUniqueDeduper(), group, cliOutput, writer)
 			return
 		}
+		flag := flagSet.getFlagByName(strings.ToLower(os.Args[2]))
+		if flag != nil {
+			flagSet.displaySingleFlagUsageFunc(os.Args[2], flag, cliOutput, writer)
+			return
+		}
 	}
 
 	if len(flagSet.groups) > 0 {
@@ -548,6 +552,17 @@ func (flagSet *FlagSet) getGroupbyName(name string) groupData {
 	return groupData{}
 }
 
+func (flagSet *FlagSet) getFlagByName(name string) *FlagData {
+	var flagData *FlagData
+	flagSet.flagKeys.forEach(func(key string, data *FlagData) {
+		if strings.EqualFold(data.long, name) || strings.EqualFold(data.short, name) {
+			flagData = data
+			return
+		}
+	})
+	return flagData
+}
+
 // usageFuncInternal prints usage for command line flags
 func (flagSet *FlagSet) usageFuncInternal(writer *tabwriter.Writer) {
 	uniqueDeduper := newUniqueDeduper()
@@ -614,6 +629,15 @@ func (flagSet *FlagSet) displayGroupUsageFunc(uniqueDeduper *uniqueDeduper, grou
 	return otherOptions
 }
 
+// displaySingleFlagUsageFunc displays usage for a single flag
+func (flagSet *FlagSet) displaySingleFlagUsageFunc(name string, data *FlagData, cliOutput io.Writer, writer *tabwriter.Writer) {
+	if currentFlag := flagSet.CommandLine.Lookup(name); currentFlag != nil {
+		result := createUsageString(data, currentFlag)
+		fmt.Fprint(writer, result, "\n")
+		writer.Flush()
+	}
+}
+
 type uniqueDeduper struct {
 	hashes map[string]interface{}
 }

goflags_test.go

@@ -3,7 +3,6 @@ package goflags
 import (
 	"bytes"
 	"flag"
-	"io/ioutil"
 	"os"
 	"reflect"
 	"strconv"
@@ -63,7 +62,7 @@ severity:
 int-value: 543
 bool-value: true
 duration-value: 1h`
-	err := ioutil.WriteFile("test.yaml", []byte(configFileData), os.ModePerm)
+	err := os.WriteFile("test.yaml", []byte(configFileData), os.ModePerm)
 	require.Nil(t, err, "could not write temporary config")
 	defer os.Remove("test.yaml")
 
@@ -277,7 +276,7 @@ func TestParseFileCommaSeparatedStringSlice(t *testing.T) {
 	testFileData := `value1
 Value2 "
 value3`
-	err := ioutil.WriteFile(testFile, []byte(testFileData), os.ModePerm)
+	err := os.WriteFile(testFile, []byte(testFileData), os.ModePerm)
 	require.Nil(t, err, "could not write temporary values file")
 	defer os.Remove(testFile)
 
@@ -306,7 +305,7 @@ config-only:
  - test
  - test2
  `
-	err := ioutil.WriteFile("test.yaml", []byte(configFileData), os.ModePerm)
+	err := os.WriteFile("test.yaml", []byte(configFileData), os.ModePerm)
 	require.Nil(t, err, "could not write temporary config")
 	defer os.Remove("test.yaml")