Parses usage placeholders via back quotes. Resolves #333

flag.go

@@ -74,7 +74,8 @@ type GenericFlag struct {
 // help text to the user (uses the String() method of the generic flag to show
 // the value)
 func (f GenericFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s %v\t%v", prefixedNames(f.Name), f.FormatValueHelp(), f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s %v\t%v", prefixedNames(f.Name, placeholder), f.FormatValueHelp(), usage))
 }
 
 func (f GenericFlag) FormatValueHelp() string {
@@ -143,7 +144,8 @@ type StringSliceFlag struct {
 func (f StringSliceFlag) String() string {
 	firstName := strings.Trim(strings.Split(f.Name, ",")[0], " ")
 	pref := prefixFor(firstName)
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name), pref+firstName+" option "+pref+firstName+" option", f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name, placeholder), pref+firstName+" option "+pref+firstName+" option", usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -212,7 +214,8 @@ type IntSliceFlag struct {
 func (f IntSliceFlag) String() string {
 	firstName := strings.Trim(strings.Split(f.Name, ",")[0], " ")
 	pref := prefixFor(firstName)
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name), pref+firstName+" option "+pref+firstName+" option", f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s [%v]\t%v", prefixedNames(f.Name, placeholder), pref+firstName+" option "+pref+firstName+" option", usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -257,7 +260,8 @@ type BoolFlag struct {
 
 // String returns a readable representation of this value (for usage defaults)
 func (f BoolFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s\t%v", prefixedNames(f.Name), f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s\t%v", prefixedNames(f.Name, placeholder), usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -300,7 +304,8 @@ type BoolTFlag struct {
 
 // String returns a readable representation of this value (for usage defaults)
 func (f BoolTFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s\t%v", prefixedNames(f.Name), f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s\t%v", prefixedNames(f.Name, placeholder), usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -343,7 +348,8 @@ type StringFlag struct {
 
 // String returns the usage
 func (f StringFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s %v\t%v", prefixedNames(f.Name), f.FormatValueHelp(), f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s %v\t%v", prefixedNames(f.Name, placeholder), f.FormatValueHelp(), usage))
 }
 
 func (f StringFlag) FormatValueHelp() string {
@@ -391,7 +397,8 @@ type IntFlag struct {
 
 // String returns the usage
 func (f IntFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name, placeholder), f.Value, usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -434,7 +441,8 @@ type DurationFlag struct {
 
 // String returns a readable representation of this value (for usage defaults)
 func (f DurationFlag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name, placeholder), f.Value, usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -477,7 +485,8 @@ type Float64Flag struct {
 
 // String returns the usage
 func (f Float64Flag) String() string {
-	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name), f.Value, f.Usage))
+	placeholder, usage := unquoteUsage(f.Usage)
+	return withEnvHint(f.EnvVar, fmt.Sprintf("%s \"%v\"\t%v", prefixedNames(f.Name, placeholder), f.Value, usage))
 }
 
 // Apply populates the flag given the flag set and environment
@@ -517,16 +526,37 @@ func prefixFor(name string) (prefix string) {
 	return
 }
 
-func prefixedNames(fullName string) (prefixed string) {
+// Returns the placeholder, if any, and the unquoted usage string.
+func unquoteUsage(usage string) (string, string) {
+	for i := 0; i < len(usage); i++ {
+		if usage[i] == '`' {
+			for j := i + 1; j < len(usage); j++ {
+				if usage[j] == '`' {
+					name := usage[i+1 : j]
+					usage = usage[:i] + name + usage[j+1:]
+					return name, usage
+				}
+			}
+			break
+		}
+	}
+	return "", usage
+}
+
+func prefixedNames(fullName, placeholder string) string {
+	var prefixed string
 	parts := strings.Split(fullName, ",")
 	for i, name := range parts {
 		name = strings.Trim(name, " ")
 		prefixed += prefixFor(name) + name
+		if placeholder != "" {
+			prefixed += " " + placeholder
+		}
 		if i < len(parts)-1 {
 			prefixed += ", "
 		}
 	}
-	return
+	return prefixed
 }
 
 func withEnvHint(envVar, str string) string {

flag_test.go

@@ -4,9 +4,9 @@ import (
 	"fmt"
 	"os"
 	"reflect"
+	"runtime"
 	"strings"
 	"testing"
-	"runtime"
 )
 
 var boolFlagTests = []struct {
@@ -31,19 +31,21 @@ func TestBoolFlagHelpOutput(t *testing.T) {
 
 var stringFlagTests = []struct {
 	name     string
+	usage    string
 	value    string
 	expected string
 }{
-	{"help", "", "--help \t"},
+	{"help", "", "", "--help \t"},
-	{"h", "", "-h \t"},
+	{"h", "", "", "-h \t"},
-	{"h", "", "-h \t"},
+	{"h", "", "", "-h \t"},
-	{"test", "Something", "--test \"Something\"\t"},
+	{"test", "", "Something", "--test \"Something\"\t"},
+	{"config,c", "Load configuration from `FILE`", "", "--config FILE, -c FILE \tLoad configuration from FILE"},
 }
 
 func TestStringFlagHelpOutput(t *testing.T) {
 
 	for _, test := range stringFlagTests {
-		flag := StringFlag{Name: test.name, Value: test.value}
+		flag := StringFlag{Name: test.name, Usage: test.usage, Value: test.value}
 		output := flag.String()
 
 		if output != test.expected {