factor setSlice into its own file, add setMap, and add tests for both

parse.go

@@ -702,37 +702,6 @@ func (p *Parser) val(dest path) reflect.Value {
 	return v
 }
 
-// parse a value as the appropriate type and store it in the struct
-func setSlice(dest reflect.Value, values []string, trunc bool) error {
-	if !dest.CanSet() {
-		return fmt.Errorf("field is not writable")
-	}
-
-	var ptr bool
-	elem := dest.Type().Elem()
-	if elem.Kind() == reflect.Ptr && !elem.Implements(textUnmarshalerType) {
-		ptr = true
-		elem = elem.Elem()
-	}
-
-	// Truncate the dest slice in case default values exist
-	if trunc && !dest.IsNil() {
-		dest.SetLen(0)
-	}
-
-	for _, s := range values {
-		v := reflect.New(elem)
-		if err := scalar.ParseValue(v.Elem(), s); err != nil {
-			return err
-		}
-		if !ptr {
-			v = v.Elem()
-		}
-		dest.Set(reflect.Append(dest, v))
-	}
-	return nil
-}
-
 // findOption finds an option from its name, or returns null if no spec is found
 func findOption(specs []*spec, name string) *spec {
 	for _, spec := range specs {

sequence.go

@@ -0,0 +1,108 @@
+package arg
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	scalar "github.com/alexflint/go-scalar"
+)
+
+// setSlice parses a sequence of strings and inserts them into a slice. If clear
+// is true then any values already in the slice are removed.
+func setSlice(dest reflect.Value, values []string, clear bool) error {
+	if !dest.CanSet() {
+		return fmt.Errorf("field is not writable")
+	}
+
+	var ptr bool
+	elem := dest.Type().Elem()
+	if elem.Kind() == reflect.Ptr && !elem.Implements(textUnmarshalerType) {
+		ptr = true
+		elem = elem.Elem()
+	}
+
+	// clear the slice in case default values exist
+	if clear && !dest.IsNil() {
+		dest.SetLen(0)
+	}
+
+	// parse the values one-by-one
+	for _, s := range values {
+		v := reflect.New(elem)
+		if err := scalar.ParseValue(v.Elem(), s); err != nil {
+			return err
+		}
+		if !ptr {
+			v = v.Elem()
+		}
+		dest.Set(reflect.Append(dest, v))
+	}
+	return nil
+}
+
+// setMap parses a sequence of name=value strings and inserts them into a map.
+// If clear is true then any values already in the map are removed.
+func setMap(dest reflect.Value, values []string, clear bool) error {
+	if !dest.CanSet() {
+		return fmt.Errorf("field is not writable")
+	}
+
+	// determine the key and value type
+	var keyIsPtr bool
+	keyType := dest.Type().Key()
+	if keyType.Kind() == reflect.Ptr && !keyType.Implements(textUnmarshalerType) {
+		keyIsPtr = true
+		keyType = keyType.Elem()
+	}
+
+	var valIsPtr bool
+	valType := dest.Type().Elem()
+	if valType.Kind() == reflect.Ptr && !valType.Implements(textUnmarshalerType) {
+		valIsPtr = true
+		valType = valType.Elem()
+	}
+
+	// clear the slice in case default values exist
+	if clear && !dest.IsNil() {
+		for _, k := range dest.MapKeys() {
+			dest.SetMapIndex(k, reflect.Value{})
+		}
+	}
+
+	// allocate the map if it is not allocated
+	if dest.IsNil() {
+		dest.Set(reflect.MakeMap(dest.Type()))
+	}
+
+	// parse the values one-by-one
+	for _, s := range values {
+		// split at the first equals sign
+		pos := strings.Index(s, "=")
+		if pos == -1 {
+			return fmt.Errorf("cannot parse %q into a map, expected format key=value", s)
+		}
+
+		// parse the key
+		k := reflect.New(keyType)
+		if err := scalar.ParseValue(k.Elem(), s[:pos]); err != nil {
+			return err
+		}
+		if !keyIsPtr {
+			k = k.Elem()
+		}
+
+		// parse the value
+		v := reflect.New(valType)
+		if err := scalar.ParseValue(v.Elem(), s[pos+1:]); err != nil {
+			return err
+		}
+		if !valIsPtr {
+			v = v.Elem()
+		}
+
+		// add it to the map
+		dest.SetMapIndex(k, v)
+	}
+	return nil
+}

sequence_test.go

@@ -0,0 +1,81 @@
+package arg
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSetSliceWithoutClearing(t *testing.T) {
+	xs := []int{10}
+	entries := []string{"1", "2", "3"}
+	err := setSlice(reflect.ValueOf(&xs).Elem(), entries, false)
+	require.NoError(t, err)
+	assert.Equal(t, []int{10, 1, 2, 3}, xs)
+}
+
+func TestSetSliceWithClear(t *testing.T) {
+	xs := []int{100}
+	entries := []string{"1", "2", "3"}
+	err := setSlice(reflect.ValueOf(&xs).Elem(), entries, true)
+	require.NoError(t, err)
+	assert.Equal(t, []int{1, 2, 3}, xs)
+}
+
+func TestSetSlicePtr(t *testing.T) {
+	var xs []*int
+	entries := []string{"1", "2", "3"}
+	err := setSlice(reflect.ValueOf(&xs).Elem(), entries, true)
+	require.NoError(t, err)
+	require.Len(t, xs, 3)
+	assert.Equal(t, 1, *xs[0])
+	assert.Equal(t, 2, *xs[1])
+	assert.Equal(t, 3, *xs[2])
+}
+
+func TestSetSliceTextUnmarshaller(t *testing.T) {
+	// textUnmarshaler is a struct that captures the length of the string passed to it
+	var xs []*textUnmarshaler
+	entries := []string{"a", "aa", "aaa"}
+	err := setSlice(reflect.ValueOf(&xs).Elem(), entries, true)
+	require.NoError(t, err)
+	require.Len(t, xs, 3)
+	assert.Equal(t, 1, xs[0].val)
+	assert.Equal(t, 2, xs[1].val)
+	assert.Equal(t, 3, xs[2].val)
+}
+
+func TestSetMapWithoutClearing(t *testing.T) {
+	m := map[string]int{"foo": 10}
+	entries := []string{"a=1", "b=2"}
+	err := setMap(reflect.ValueOf(&m).Elem(), entries, false)
+	require.NoError(t, err)
+	require.Len(t, m, 3)
+	assert.Equal(t, 1, m["a"])
+	assert.Equal(t, 2, m["b"])
+	assert.Equal(t, 10, m["foo"])
+}
+
+func TestSetMapWithClear(t *testing.T) {
+	m := map[string]int{"foo": 10}
+	entries := []string{"a=1", "b=2"}
+	err := setMap(reflect.ValueOf(&m).Elem(), entries, true)
+	require.NoError(t, err)
+	require.Len(t, m, 2)
+	assert.Equal(t, 1, m["a"])
+	assert.Equal(t, 2, m["b"])
+}
+
+func TestSetMapTextUnmarshaller(t *testing.T) {
+	// textUnmarshaler is a struct that captures the length of the string passed to it
+	var m map[textUnmarshaler]*textUnmarshaler
+	entries := []string{"a=123", "aa=12", "aaa=1"}
+	err := setMap(reflect.ValueOf(&m).Elem(), entries, true)
+	require.NoError(t, err)
+	require.Len(t, m, 3)
+	assert.Equal(t, &textUnmarshaler{3}, m[textUnmarshaler{1}])
+	assert.Equal(t, &textUnmarshaler{2}, m[textUnmarshaler{2}])
+	assert.Equal(t, &textUnmarshaler{1}, m[textUnmarshaler{3}])
+}