Merge pull request #83 from alexflint/tweak-examples

Add expected outputs to all runnable examples

example_test.go

@@ -3,12 +3,17 @@ package arg
 import (
 	"fmt"
 	"os"
+	"strings"
 )
 
+func split(s string) []string {
+	return strings.Split(s, " ")
+}
+
 // This example demonstrates basic usage
 func Example() {
 	// These are the args you would pass in on the command line
-	os.Args = []string{"./example", "--foo=hello", "--bar"}
+	os.Args = split("./example --foo=hello --bar")
 
 	var args struct {
 		Foo string
@@ -16,65 +21,72 @@ func Example() {
 	}
 	MustParse(&args)
 	fmt.Println(args.Foo, args.Bar)
+	// output: hello true
 }
 
 // This example demonstrates arguments that have default values
 func Example_defaultValues() {
 	// These are the args you would pass in on the command line
-	os.Args = []string{"--help"}
+	os.Args = split("./example")
 
 	var args struct {
 		Foo string
-		Bar bool
 	}
 	args.Foo = "default value"
 	MustParse(&args)
-	fmt.Println(args.Foo, args.Bar)
+	fmt.Println(args.Foo)
+	// output: default value
 }
 
 // This example demonstrates arguments that are required
 func Example_requiredArguments() {
 	// These are the args you would pass in on the command line
-	os.Args = []string{"--foo=1", "--bar"}
+	os.Args = split("./example --foo=abc --bar")
 
 	var args struct {
 		Foo string `arg:"required"`
 		Bar bool
 	}
 	MustParse(&args)
+	fmt.Println(args.Foo, args.Bar)
+	// output: abc true
 }
 
 // This example demonstrates positional arguments
 func Example_positionalArguments() {
 	// These are the args you would pass in on the command line
-	os.Args = []string{"./example", "in", "out1", "out2", "out3"}
+	os.Args = split("./example in out1 out2 out3")
 
 	var args struct {
 		Input  string   `arg:"positional"`
 		Output []string `arg:"positional"`
 	}
 	MustParse(&args)
-	fmt.Println("Input:", args.Input)
+	fmt.Println("In:", args.Input)
-	fmt.Println("Output:", args.Output)
+	fmt.Println("Out:", args.Output)
+	// output:
+	// In: in
+	// Out: [out1 out2 out3]
 }
 
 // This example demonstrates arguments that have multiple values
 func Example_multipleValues() {
 	// The args you would pass in on the command line
-	os.Args = []string{"--help"}
+	os.Args = split("./example --database localhost --ids 1 2 3")
 
 	var args struct {
 		Database string
 		IDs      []int64
 	}
 	MustParse(&args)
-	fmt.Printf("Fetching the following IDs from %s: %q", args.Database, args.IDs)
+	fmt.Printf("Fetching the following IDs from %s: %v", args.Database, args.IDs)
+	// output: Fetching the following IDs from localhost: [1 2 3]
 }
 
 // This eample demonstrates multiple value arguments that can be mixed with
 // other arguments.
 func Example_multipleMixed() {
-	os.Args = []string{"./example", "-c", "cmd1", "db1", "-f", "file1", "db2", "-c", "cmd2", "-f", "file2", "-f", "file3", "db3", "-c", "cmd3"}
+	os.Args = split("./example -c cmd1 db1 -f file1 db2 -c cmd2 -f file2 -f file3 db3 -c cmd3")
 	var args struct {
 		Commands  []string `arg:"-c,separate"`
 		Files     []string `arg:"-f,separate"`
@@ -82,21 +94,44 @@ func Example_multipleMixed() {
 	}
 	MustParse(&args)
 	fmt.Println("Commands:", args.Commands)
-	fmt.Println("Files", args.Files)
+	fmt.Println("Files:", args.Files)
-	fmt.Println("Databases", args.Databases)
+	fmt.Println("Databases:", args.Databases)
+
+	// output:
+	// Commands: [cmd1 cmd2 cmd3]
+	// Files: [file1 file2 file3]
+	// Databases: [db1 db2 db3]
 }
 
 // This example shows the usage string generated by go-arg
 func Example_usageString() {
 	// These are the args you would pass in on the command line
-	os.Args = []string{"--help"}
+	os.Args = split("./example --help")
 
 	var args struct {
 		Input    string   `arg:"positional"`
 		Output   []string `arg:"positional"`
-		Verbose  bool     `arg:"-v,help:verbosity level"`
+		Verbose  bool     `arg:"-v" help:"verbosity level"`
-		Dataset  string   `arg:"help:dataset to use"`
+		Dataset  string   `help:"dataset to use"`
 		Optimize int      `arg:"-O,help:optimization level"`
 	}
+
+	// This is only necessary when running inside golang's runnable example harness
+	osExit = func(int) {}
+
 	MustParse(&args)
+
+	// output:
+	// Usage: example [--verbose] [--dataset DATASET] [--optimize OPTIMIZE] INPUT [OUTPUT [OUTPUT ...]]
+	//
+	// Positional arguments:
+	//   INPUT
+	//   OUTPUT
+	//
+	// Options:
+	//   --verbose, -v          verbosity level
+	//   --dataset DATASET      dataset to use
+	//   --optimize OPTIMIZE, -O OPTIMIZE
+	//                          optimization level
+	//   --help, -h             display this help and exit
 }

parse.go

@@ -13,6 +13,9 @@ import (
 	scalar "github.com/alexflint/go-scalar"
 )
 
+// to enable monkey-patching during tests
+var osExit = os.Exit
+
 // spec represents a command line option
 type spec struct {
 	dest       reflect.Value
@@ -38,20 +41,21 @@ func MustParse(dest ...interface{}) *Parser {
 	p, err := NewParser(Config{}, dest...)
 	if err != nil {
 		fmt.Println(err)
-		os.Exit(-1)
+		osExit(-1)
 	}
+
 	err = p.Parse(flags())
-	if err == ErrHelp {
+	switch {
+	case err == ErrHelp:
 		p.WriteHelp(os.Stdout)
-		os.Exit(0)
+		osExit(0)
-	}
+	case err == ErrVersion:
-	if err == ErrVersion {
 		fmt.Println(p.version)
-		os.Exit(0)
+		osExit(0)
-	}
+	case err != nil:
-	if err != nil {
 		p.Fail(err.Error())
 	}
+
 	return p
 }