Prefer fmt.Fprint* functions over io.WriteString

Less composition needed.

app.go

@@ -112,18 +112,18 @@ func (a *App) Run(arguments []string) error {
 	err := set.Parse(arguments[1:])
 	nerr := normalizeFlags(a.Flags, set)
 	if nerr != nil {
-		io.WriteString(a.Writer, fmt.Sprintln(nerr))
+		fmt.Fprintln(a.Writer, nerr)
 		context := NewContext(a, set, set)
 		ShowAppHelp(context)
-		io.WriteString(a.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(a.Writer)
 		return nerr
 	}
 	context := NewContext(a, set, set)
 
 	if err != nil {
-		io.WriteString(a.Writer, fmt.Sprintf("Incorrect Usage.\n\n"))
+		fmt.Fprintf(a.Writer, "Incorrect Usage.\n\n")
 		ShowAppHelp(context)
-		io.WriteString(a.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(a.Writer)
 		return err
 	}
 
@@ -163,7 +163,7 @@ func (a *App) Run(arguments []string) error {
 // Another entry point to the cli app, takes care of passing arguments and error handling
 func (a *App) RunAndExitOnError() {
 	if err := a.Run(os.Args); err != nil {
-		os.Stderr.WriteString(fmt.Sprintln(err))
+		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
 }
@@ -191,18 +191,18 @@ func (a *App) RunAsSubcommand(ctx *Context) error {
 	context := NewContext(a, set, ctx.globalSet)
 
 	if nerr != nil {
-		io.WriteString(a.Writer, fmt.Sprintln(nerr))
+		fmt.Fprintln(a.Writer, nerr)
 		if len(a.Commands) > 0 {
 			ShowSubcommandHelp(context)
 		} else {
 			ShowCommandHelp(ctx, context.Args().First())
 		}
-		io.WriteString(a.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(a.Writer)
 		return nerr
 	}
 
 	if err != nil {
-		io.WriteString(a.Writer, fmt.Sprintf("Incorrect Usage.\n\n"))
+		fmt.Fprintf(a.Writer, "Incorrect Usage.\n\n")
 		ShowSubcommandHelp(context)
 		return err
 	}

command.go

@@ -2,7 +2,6 @@ package cli
 
 import (
 	"fmt"
-	"io"
 	"io/ioutil"
 	"strings"
 )
@@ -75,18 +74,18 @@ func (c Command) Run(ctx *Context) error {
 	}
 
 	if err != nil {
-		io.WriteString(ctx.App.Writer, fmt.Sprintf("Incorrect Usage.\n\n"))
+		fmt.Fprint(ctx.App.Writer, "Incorrect Usage.\n\n")
 		ShowCommandHelp(ctx, c.Name)
-		io.WriteString(ctx.App.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(ctx.App.Writer)
 		return err
 	}
 
 	nerr := normalizeFlags(c.Flags, set)
 	if nerr != nil {
-		io.WriteString(ctx.App.Writer, fmt.Sprintln(nerr))
-		io.WriteString(ctx.App.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(ctx.App.Writer, nerr)
+		fmt.Fprintln(ctx.App.Writer)
 		ShowCommandHelp(ctx, c.Name)
-		io.WriteString(ctx.App.Writer, fmt.Sprintln(""))
+		fmt.Fprintln(ctx.App.Writer)
 		return nerr
 	}
 	context := NewContext(ctx.App, set, ctx.globalSet)

help.go

@@ -1,9 +1,6 @@
 package cli
 
-import (
-	"fmt"
-	"io"
-)
+import "fmt"
 
 // The text template for the Default help topic.
 // cli.go uses text/template to render templates. You can
@@ -106,9 +103,9 @@ func ShowAppHelp(c *Context) {
 // Prints the list of subcommands as the default app completion method
 func DefaultAppComplete(c *Context) {
 	for _, command := range c.App.Commands {
-		io.WriteString(c.App.Writer, fmt.Sprintln(command.Name))
+		fmt.Fprintln(c.App.Writer, command.Name)
 		if command.ShortName != "" {
-			io.WriteString(c.App.Writer, fmt.Sprintln(command.ShortName))
+			fmt.Fprintln(c.App.Writer, command.ShortName)
 		}
 	}
 }
@@ -125,7 +122,7 @@ func ShowCommandHelp(c *Context, command string) {
 	if c.App.CommandNotFound != nil {
 		c.App.CommandNotFound(c, command)
 	} else {
-		io.WriteString(c.App.Writer, fmt.Sprintf("No help topic for '%v'\n", command))
+		fmt.Fprintf(c.App.Writer, "No help topic for '%v'\n", command)
 	}
 }
 
@@ -140,7 +137,7 @@ func ShowVersion(c *Context) {
 }
 
 func printVersion(c *Context) {
-	io.WriteString(c.App.Writer, fmt.Sprintf("%v version %v\n", c.App.Name, c.App.Version))
+	fmt.Fprintf(c.App.Writer, "%v version %v\n", c.App.Name, c.App.Version)
 }
 
 // Prints the lists of commands within a given context