basic first version working

This commit is contained in:
Alex Flint 2015-10-31 16:15:24 -07:00
commit 408290f7c2
2 changed files with 356 additions and 0 deletions

268
parse.go Normal file
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package arguments
import (
"fmt"
"os"
"reflect"
"strconv"
"strings"
)
// MustParse processes command line arguments and exits upon failure.
func MustParse(dest interface{}) {
err := Parse(dest)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
}
// Parse processes command line arguments and stores the result in args.
func Parse(dest interface{}) error {
return ParseFrom(dest, os.Args)
}
// ParseFrom processes command line arguments and stores the result in args.
func ParseFrom(dest interface{}, args []string) error {
v := reflect.ValueOf(dest)
if v.Kind() != reflect.Ptr {
panic(fmt.Sprintf("%s is not a pointer type", v.Type().Name()))
}
v = v.Elem()
// Parse the spec
spec, err := extractSpec(v.Type())
if err != nil {
return err
}
// Process args
err = processArgs(v, spec, args)
if err != nil {
return err
}
// Validate
return validate(spec)
}
// spec represents information about an argument extracted from struct tags
type spec struct {
field reflect.StructField
index int
long string
short string
multiple bool
required bool
positional bool
help string
wasPresent bool
}
// extractSpec gets specifications for each argument from the tags in a struct
func extractSpec(t reflect.Type) ([]*spec, error) {
if t.Kind() != reflect.Struct {
panic(fmt.Sprintf("%s is not a struct pointer", t.Name()))
}
var specs []*spec
for i := 0; i < t.NumField(); i++ {
// Check for the ignore switch in the tag
field := t.Field(i)
tag := field.Tag.Get("arg")
if tag == "-" {
continue
}
spec := spec{
long: strings.ToLower(field.Name),
field: field,
index: i,
}
// Get the scalar type for this field
scalarType := field.Type
if scalarType.Kind() == reflect.Slice {
spec.multiple = true
scalarType = scalarType.Elem()
if scalarType.Kind() == reflect.Ptr {
scalarType = scalarType.Elem()
}
}
// Check for unsupported types
switch scalarType.Kind() {
case reflect.Array, reflect.Chan, reflect.Func, reflect.Interface,
reflect.Map, reflect.Ptr, reflect.Struct,
reflect.Complex64, reflect.Complex128:
return nil, fmt.Errorf("%s.%s: %s fields are not supported", t.Name(), field.Name, scalarType.Kind())
}
// Look at the tag
if tag != "" {
for _, key := range strings.Split(tag, ",") {
var value string
if pos := strings.Index(key, ":"); pos != -1 {
value = key[pos+1:]
key = key[:pos]
}
switch {
case strings.HasPrefix(key, "--"):
spec.long = key[2:]
case strings.HasPrefix(key, "-"):
if len(key) != 2 {
return nil, fmt.Errorf("%s.%s: short arguments must be one character only", t.Name(), field.Name)
}
spec.short = key[1:]
case key == "required":
spec.required = true
case key == "positional":
spec.positional = true
case key == "help":
spec.help = value
default:
return nil, fmt.Errorf("unrecognized tag '%s' on field %s", key, tag)
}
}
}
specs = append(specs, &spec)
}
return specs, nil
}
// processArgs processes arguments using a pre-constructed spec
func processArgs(dest reflect.Value, specs []*spec, args []string) error {
// construct a map from arg name to spec
specByName := make(map[string]*spec)
for _, spec := range specs {
if spec.long != "" {
specByName[spec.long] = spec
}
if spec.short != "" {
specByName[spec.short] = spec
}
}
// process each string from the command line
var allpositional bool
var positionals []string
// must use explicit for loop, not range, because we manipulate i inside the loop
for i := 0; i < len(args); i++ {
arg := args[i]
if arg == "--" {
allpositional = true
continue
}
if !strings.HasPrefix(arg, "-") || allpositional {
positionals = append(positionals, arg)
continue
}
// check for an equals sign, as in "--foo=bar"
var value string
opt := strings.TrimLeft(arg, "-")
if pos := strings.Index(opt, "="); pos != -1 {
value = opt[pos+1:]
opt = opt[:pos]
}
// lookup the spec for this option
spec, ok := specByName[opt]
if !ok {
return fmt.Errorf("unknown argument %s", arg)
}
spec.wasPresent = true
// deal with the case of multiple values
if spec.multiple {
var values []string
if value == "" {
for i++; i < len(args) && !strings.HasPrefix(args[i], "-"); i++ {
values = append(values, args[i])
}
} else {
values = append(values, value)
}
setSlice(dest, spec, values)
continue
}
// if it's a flag and it has no value then set the value to true
if spec.field.Type.Kind() == reflect.Bool && value == "" {
value = "true"
}
// if we have something like "--foo" then the value is the next argument
if value == "" {
if i+1 == len(args) || strings.HasPrefix(args[i+1], "-") {
return fmt.Errorf("missing value for %s", arg)
}
value = args[i+1]
i++
}
err := setScalar(dest.Field(spec.index), value)
if err != nil {
return fmt.Errorf("error processing %s: %v", arg, err)
}
}
return nil
}
// validate an argument spec after arguments have been parse
func validate(spec []*spec) error {
for _, arg := range spec {
if arg.required && !arg.wasPresent {
return fmt.Errorf("--%s is required", strings.ToLower(arg.field.Name))
}
}
return nil
}
// parse a value as the apropriate type and store it in the struct
func setSlice(dest reflect.Value, spec *spec, values []string) error {
// TODO
return nil
}
// set a value from a string
func setScalar(v reflect.Value, s string) error {
if !v.CanSet() {
return fmt.Errorf("field is not writable")
}
switch v.Kind() {
case reflect.String:
v.Set(reflect.ValueOf(s))
case reflect.Bool:
x, err := strconv.ParseBool(s)
if err != nil {
return err
}
v.Set(reflect.ValueOf(x))
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
x, err := strconv.ParseInt(s, 10, v.Type().Bits())
if err != nil {
return err
}
v.Set(reflect.ValueOf(x).Convert(v.Type()))
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
x, err := strconv.ParseUint(s, 10, v.Type().Bits())
if err != nil {
return err
}
v.Set(reflect.ValueOf(x).Convert(v.Type()))
case reflect.Float32, reflect.Float64:
x, err := strconv.ParseFloat(s, v.Type().Bits())
if err != nil {
return err
}
v.Set(reflect.ValueOf(x).Convert(v.Type()))
default:
return fmt.Errorf("not a scalar type: %s", v.Kind())
}
return nil
}

88
parse_test.go Normal file
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package arguments
import (
"strings"
"testing"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)
func split(s string) []string {
return strings.Split(s, " ")
}
func TestStringSingle(t *testing.T) {
var args struct {
Foo string
}
err := ParseFrom(&args, split("--foo bar"))
require.NoError(t, err)
assert.Equal(t, "bar", args.Foo)
}
func TestMixed(t *testing.T) {
var args struct {
Foo string `arg:"-f"`
Bar int
Ham bool
Spam float32
}
args.Bar = 3
err := ParseFrom(&args, split("-spam=1.2 -ham -f xyz"))
require.NoError(t, err)
assert.Equal(t, "xyz", args.Foo)
assert.Equal(t, 3, args.Bar)
assert.Equal(t, true, args.Ham)
assert.Equal(t, 1.2, args.Spam)
}
func TestRequired(t *testing.T) {
var args struct {
Foo string `arg:"required"`
}
err := ParseFrom(&args, nil)
require.Error(t, err, "--foo is required")
}
func TestShortFlag(t *testing.T) {
var args struct {
Foo string `arg:"-f"`
}
err := ParseFrom(&args, split("-f xyz"))
require.NoError(t, err)
assert.Equal(t, "xyz", args.Foo)
err = ParseFrom(&args, split("-foo xyz"))
require.NoError(t, err)
assert.Equal(t, "xyz", args.Foo)
err = ParseFrom(&args, split("--foo xyz"))
require.NoError(t, err)
assert.Equal(t, "xyz", args.Foo)
}
func TestCaseSensitive(t *testing.T) {
var args struct {
Lower bool `arg:"-v"`
Upper bool `arg:"-V"`
}
err := ParseFrom(&args, split("-v"))
require.NoError(t, err)
assert.True(t, args.Lower)
assert.False(t, args.Upper)
}
func TestCaseSensitive2(t *testing.T) {
var args struct {
Lower bool `arg:"-v"`
Upper bool `arg:"-V"`
}
err := ParseFrom(&args, split("-V"))
require.NoError(t, err)
assert.False(t, args.Lower)
assert.True(t, args.Upper)
}