Implement Cobra CLI tooling, Viper config tooling (#336)

* start pulling out + replacing urfave and config

* replace many many instances of config

* move more stuff => viper

* properly remove urfave

* move some flags to root command

* add testrig commands to root

* alias config file keys

* start adding cli parsing tests

* reorder viper init

* remove config path alias

* fmt

* change config file keys to non-nested

* we're more or less in business now

* tidy up the common func

* go fmt

* get tests passing again

* add note about the cliparsing tests

* reorganize

* update docs with changes

* structure cmd dir better

* rename + move some files around

* fix dangling comma

vendor/gopkg.in/ini.v1/struct.go

@@ -0,0 +1,747 @@
+// Copyright 2014 Unknwon
+//
+// Licensed under the Apache License, Version 2.0 (the "License"): you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+package ini
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"reflect"
+	"strings"
+	"time"
+	"unicode"
+)
+
+// NameMapper represents a ini tag name mapper.
+type NameMapper func(string) string
+
+// Built-in name getters.
+var (
+	// SnackCase converts to format SNACK_CASE.
+	SnackCase NameMapper = func(raw string) string {
+		newstr := make([]rune, 0, len(raw))
+		for i, chr := range raw {
+			if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
+				if i > 0 {
+					newstr = append(newstr, '_')
+				}
+			}
+			newstr = append(newstr, unicode.ToUpper(chr))
+		}
+		return string(newstr)
+	}
+	// TitleUnderscore converts to format title_underscore.
+	TitleUnderscore NameMapper = func(raw string) string {
+		newstr := make([]rune, 0, len(raw))
+		for i, chr := range raw {
+			if isUpper := 'A' <= chr && chr <= 'Z'; isUpper {
+				if i > 0 {
+					newstr = append(newstr, '_')
+				}
+				chr -= 'A' - 'a'
+			}
+			newstr = append(newstr, chr)
+		}
+		return string(newstr)
+	}
+)
+
+func (s *Section) parseFieldName(raw, actual string) string {
+	if len(actual) > 0 {
+		return actual
+	}
+	if s.f.NameMapper != nil {
+		return s.f.NameMapper(raw)
+	}
+	return raw
+}
+
+func parseDelim(actual string) string {
+	if len(actual) > 0 {
+		return actual
+	}
+	return ","
+}
+
+var reflectTime = reflect.TypeOf(time.Now()).Kind()
+
+// setSliceWithProperType sets proper values to slice based on its type.
+func setSliceWithProperType(key *Key, field reflect.Value, delim string, allowShadow, isStrict bool) error {
+	var strs []string
+	if allowShadow {
+		strs = key.StringsWithShadows(delim)
+	} else {
+		strs = key.Strings(delim)
+	}
+
+	numVals := len(strs)
+	if numVals == 0 {
+		return nil
+	}
+
+	var vals interface{}
+	var err error
+
+	sliceOf := field.Type().Elem().Kind()
+	switch sliceOf {
+	case reflect.String:
+		vals = strs
+	case reflect.Int:
+		vals, err = key.parseInts(strs, true, false)
+	case reflect.Int64:
+		vals, err = key.parseInt64s(strs, true, false)
+	case reflect.Uint:
+		vals, err = key.parseUints(strs, true, false)
+	case reflect.Uint64:
+		vals, err = key.parseUint64s(strs, true, false)
+	case reflect.Float64:
+		vals, err = key.parseFloat64s(strs, true, false)
+	case reflect.Bool:
+		vals, err = key.parseBools(strs, true, false)
+	case reflectTime:
+		vals, err = key.parseTimesFormat(time.RFC3339, strs, true, false)
+	default:
+		return fmt.Errorf("unsupported type '[]%s'", sliceOf)
+	}
+	if err != nil && isStrict {
+		return err
+	}
+
+	slice := reflect.MakeSlice(field.Type(), numVals, numVals)
+	for i := 0; i < numVals; i++ {
+		switch sliceOf {
+		case reflect.String:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]string)[i]))
+		case reflect.Int:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]int)[i]))
+		case reflect.Int64:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]int64)[i]))
+		case reflect.Uint:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]uint)[i]))
+		case reflect.Uint64:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]uint64)[i]))
+		case reflect.Float64:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]float64)[i]))
+		case reflect.Bool:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]bool)[i]))
+		case reflectTime:
+			slice.Index(i).Set(reflect.ValueOf(vals.([]time.Time)[i]))
+		}
+	}
+	field.Set(slice)
+	return nil
+}
+
+func wrapStrictError(err error, isStrict bool) error {
+	if isStrict {
+		return err
+	}
+	return nil
+}
+
+// setWithProperType sets proper value to field based on its type,
+// but it does not return error for failing parsing,
+// because we want to use default value that is already assigned to struct.
+func setWithProperType(t reflect.Type, key *Key, field reflect.Value, delim string, allowShadow, isStrict bool) error {
+	vt := t
+	isPtr := t.Kind() == reflect.Ptr
+	if isPtr {
+		vt = t.Elem()
+	}
+	switch vt.Kind() {
+	case reflect.String:
+		stringVal := key.String()
+		if isPtr {
+			field.Set(reflect.ValueOf(&stringVal))
+		} else if len(stringVal) > 0 {
+			field.SetString(key.String())
+		}
+	case reflect.Bool:
+		boolVal, err := key.Bool()
+		if err != nil {
+			return wrapStrictError(err, isStrict)
+		}
+		if isPtr {
+			field.Set(reflect.ValueOf(&boolVal))
+		} else {
+			field.SetBool(boolVal)
+		}
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		// ParseDuration will not return err for `0`, so check the type name
+		if vt.Name() == "Duration" {
+			durationVal, err := key.Duration()
+			if err != nil {
+				if intVal, err := key.Int64(); err == nil {
+					field.SetInt(intVal)
+					return nil
+				}
+				return wrapStrictError(err, isStrict)
+			}
+			if isPtr {
+				field.Set(reflect.ValueOf(&durationVal))
+			} else if int64(durationVal) > 0 {
+				field.Set(reflect.ValueOf(durationVal))
+			}
+			return nil
+		}
+
+		intVal, err := key.Int64()
+		if err != nil {
+			return wrapStrictError(err, isStrict)
+		}
+		if isPtr {
+			pv := reflect.New(t.Elem())
+			pv.Elem().SetInt(intVal)
+			field.Set(pv)
+		} else {
+			field.SetInt(intVal)
+		}
+	//	byte is an alias for uint8, so supporting uint8 breaks support for byte
+	case reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		durationVal, err := key.Duration()
+		// Skip zero value
+		if err == nil && uint64(durationVal) > 0 {
+			if isPtr {
+				field.Set(reflect.ValueOf(&durationVal))
+			} else {
+				field.Set(reflect.ValueOf(durationVal))
+			}
+			return nil
+		}
+
+		uintVal, err := key.Uint64()
+		if err != nil {
+			return wrapStrictError(err, isStrict)
+		}
+		if isPtr {
+			pv := reflect.New(t.Elem())
+			pv.Elem().SetUint(uintVal)
+			field.Set(pv)
+		} else {
+			field.SetUint(uintVal)
+		}
+
+	case reflect.Float32, reflect.Float64:
+		floatVal, err := key.Float64()
+		if err != nil {
+			return wrapStrictError(err, isStrict)
+		}
+		if isPtr {
+			pv := reflect.New(t.Elem())
+			pv.Elem().SetFloat(floatVal)
+			field.Set(pv)
+		} else {
+			field.SetFloat(floatVal)
+		}
+	case reflectTime:
+		timeVal, err := key.Time()
+		if err != nil {
+			return wrapStrictError(err, isStrict)
+		}
+		if isPtr {
+			field.Set(reflect.ValueOf(&timeVal))
+		} else {
+			field.Set(reflect.ValueOf(timeVal))
+		}
+	case reflect.Slice:
+		return setSliceWithProperType(key, field, delim, allowShadow, isStrict)
+	default:
+		return fmt.Errorf("unsupported type %q", t)
+	}
+	return nil
+}
+
+func parseTagOptions(tag string) (rawName string, omitEmpty bool, allowShadow bool, allowNonUnique bool, extends bool) {
+	opts := strings.SplitN(tag, ",", 5)
+	rawName = opts[0]
+	for _, opt := range opts[1:] {
+		omitEmpty = omitEmpty || (opt == "omitempty")
+		allowShadow = allowShadow || (opt == "allowshadow")
+		allowNonUnique = allowNonUnique || (opt == "nonunique")
+		extends = extends || (opt == "extends")
+	}
+	return rawName, omitEmpty, allowShadow, allowNonUnique, extends
+}
+
+// mapToField maps the given value to the matching field of the given section.
+// The sectionIndex is the index (if non unique sections are enabled) to which the value should be added.
+func (s *Section) mapToField(val reflect.Value, isStrict bool, sectionIndex int, sectionName string) error {
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+	typ := val.Type()
+
+	for i := 0; i < typ.NumField(); i++ {
+		field := val.Field(i)
+		tpField := typ.Field(i)
+
+		tag := tpField.Tag.Get("ini")
+		if tag == "-" {
+			continue
+		}
+
+		rawName, _, allowShadow, allowNonUnique, extends := parseTagOptions(tag)
+		fieldName := s.parseFieldName(tpField.Name, rawName)
+		if len(fieldName) == 0 || !field.CanSet() {
+			continue
+		}
+
+		isStruct := tpField.Type.Kind() == reflect.Struct
+		isStructPtr := tpField.Type.Kind() == reflect.Ptr && tpField.Type.Elem().Kind() == reflect.Struct
+		isAnonymousPtr := tpField.Type.Kind() == reflect.Ptr && tpField.Anonymous
+		if isAnonymousPtr {
+			field.Set(reflect.New(tpField.Type.Elem()))
+		}
+
+		if extends && (isAnonymousPtr || (isStruct && tpField.Anonymous)) {
+			if isStructPtr && field.IsNil() {
+				field.Set(reflect.New(tpField.Type.Elem()))
+			}
+			fieldSection := s
+			if rawName != "" {
+				sectionName = s.name + s.f.options.ChildSectionDelimiter + rawName
+				if secs, err := s.f.SectionsByName(sectionName); err == nil && sectionIndex < len(secs) {
+					fieldSection = secs[sectionIndex]
+				}
+			}
+			if err := fieldSection.mapToField(field, isStrict, sectionIndex, sectionName); err != nil {
+				return fmt.Errorf("map to field %q: %v", fieldName, err)
+			}
+		} else if isAnonymousPtr || isStruct || isStructPtr {
+			if secs, err := s.f.SectionsByName(fieldName); err == nil {
+				if len(secs) <= sectionIndex {
+					return fmt.Errorf("there are not enough sections (%d <= %d) for the field %q", len(secs), sectionIndex, fieldName)
+				}
+				// Only set the field to non-nil struct value if we have a section for it.
+				// Otherwise, we end up with a non-nil struct ptr even though there is no data.
+				if isStructPtr && field.IsNil() {
+					field.Set(reflect.New(tpField.Type.Elem()))
+				}
+				if err = secs[sectionIndex].mapToField(field, isStrict, sectionIndex, fieldName); err != nil {
+					return fmt.Errorf("map to field %q: %v", fieldName, err)
+				}
+				continue
+			}
+		}
+
+		// Map non-unique sections
+		if allowNonUnique && tpField.Type.Kind() == reflect.Slice {
+			newField, err := s.mapToSlice(fieldName, field, isStrict)
+			if err != nil {
+				return fmt.Errorf("map to slice %q: %v", fieldName, err)
+			}
+
+			field.Set(newField)
+			continue
+		}
+
+		if key, err := s.GetKey(fieldName); err == nil {
+			delim := parseDelim(tpField.Tag.Get("delim"))
+			if err = setWithProperType(tpField.Type, key, field, delim, allowShadow, isStrict); err != nil {
+				return fmt.Errorf("set field %q: %v", fieldName, err)
+			}
+		}
+	}
+	return nil
+}
+
+// mapToSlice maps all sections with the same name and returns the new value.
+// The type of the Value must be a slice.
+func (s *Section) mapToSlice(secName string, val reflect.Value, isStrict bool) (reflect.Value, error) {
+	secs, err := s.f.SectionsByName(secName)
+	if err != nil {
+		return reflect.Value{}, err
+	}
+
+	typ := val.Type().Elem()
+	for i, sec := range secs {
+		elem := reflect.New(typ)
+		if err = sec.mapToField(elem, isStrict, i, sec.name); err != nil {
+			return reflect.Value{}, fmt.Errorf("map to field from section %q: %v", secName, err)
+		}
+
+		val = reflect.Append(val, elem.Elem())
+	}
+	return val, nil
+}
+
+// mapTo maps a section to object v.
+func (s *Section) mapTo(v interface{}, isStrict bool) error {
+	typ := reflect.TypeOf(v)
+	val := reflect.ValueOf(v)
+	if typ.Kind() == reflect.Ptr {
+		typ = typ.Elem()
+		val = val.Elem()
+	} else {
+		return errors.New("not a pointer to a struct")
+	}
+
+	if typ.Kind() == reflect.Slice {
+		newField, err := s.mapToSlice(s.name, val, isStrict)
+		if err != nil {
+			return err
+		}
+
+		val.Set(newField)
+		return nil
+	}
+
+	return s.mapToField(val, isStrict, 0, s.name)
+}
+
+// MapTo maps section to given struct.
+func (s *Section) MapTo(v interface{}) error {
+	return s.mapTo(v, false)
+}
+
+// StrictMapTo maps section to given struct in strict mode,
+// which returns all possible error including value parsing error.
+func (s *Section) StrictMapTo(v interface{}) error {
+	return s.mapTo(v, true)
+}
+
+// MapTo maps file to given struct.
+func (f *File) MapTo(v interface{}) error {
+	return f.Section("").MapTo(v)
+}
+
+// StrictMapTo maps file to given struct in strict mode,
+// which returns all possible error including value parsing error.
+func (f *File) StrictMapTo(v interface{}) error {
+	return f.Section("").StrictMapTo(v)
+}
+
+// MapToWithMapper maps data sources to given struct with name mapper.
+func MapToWithMapper(v interface{}, mapper NameMapper, source interface{}, others ...interface{}) error {
+	cfg, err := Load(source, others...)
+	if err != nil {
+		return err
+	}
+	cfg.NameMapper = mapper
+	return cfg.MapTo(v)
+}
+
+// StrictMapToWithMapper maps data sources to given struct with name mapper in strict mode,
+// which returns all possible error including value parsing error.
+func StrictMapToWithMapper(v interface{}, mapper NameMapper, source interface{}, others ...interface{}) error {
+	cfg, err := Load(source, others...)
+	if err != nil {
+		return err
+	}
+	cfg.NameMapper = mapper
+	return cfg.StrictMapTo(v)
+}
+
+// MapTo maps data sources to given struct.
+func MapTo(v, source interface{}, others ...interface{}) error {
+	return MapToWithMapper(v, nil, source, others...)
+}
+
+// StrictMapTo maps data sources to given struct in strict mode,
+// which returns all possible error including value parsing error.
+func StrictMapTo(v, source interface{}, others ...interface{}) error {
+	return StrictMapToWithMapper(v, nil, source, others...)
+}
+
+// reflectSliceWithProperType does the opposite thing as setSliceWithProperType.
+func reflectSliceWithProperType(key *Key, field reflect.Value, delim string, allowShadow bool) error {
+	slice := field.Slice(0, field.Len())
+	if field.Len() == 0 {
+		return nil
+	}
+	sliceOf := field.Type().Elem().Kind()
+
+	if allowShadow {
+		var keyWithShadows *Key
+		for i := 0; i < field.Len(); i++ {
+			var val string
+			switch sliceOf {
+			case reflect.String:
+				val = slice.Index(i).String()
+			case reflect.Int, reflect.Int64:
+				val = fmt.Sprint(slice.Index(i).Int())
+			case reflect.Uint, reflect.Uint64:
+				val = fmt.Sprint(slice.Index(i).Uint())
+			case reflect.Float64:
+				val = fmt.Sprint(slice.Index(i).Float())
+			case reflect.Bool:
+				val = fmt.Sprint(slice.Index(i).Bool())
+			case reflectTime:
+				val = slice.Index(i).Interface().(time.Time).Format(time.RFC3339)
+			default:
+				return fmt.Errorf("unsupported type '[]%s'", sliceOf)
+			}
+
+			if i == 0 {
+				keyWithShadows = newKey(key.s, key.name, val)
+			} else {
+				_ = keyWithShadows.AddShadow(val)
+			}
+		}
+		*key = *keyWithShadows
+		return nil
+	}
+
+	var buf bytes.Buffer
+	for i := 0; i < field.Len(); i++ {
+		switch sliceOf {
+		case reflect.String:
+			buf.WriteString(slice.Index(i).String())
+		case reflect.Int, reflect.Int64:
+			buf.WriteString(fmt.Sprint(slice.Index(i).Int()))
+		case reflect.Uint, reflect.Uint64:
+			buf.WriteString(fmt.Sprint(slice.Index(i).Uint()))
+		case reflect.Float64:
+			buf.WriteString(fmt.Sprint(slice.Index(i).Float()))
+		case reflect.Bool:
+			buf.WriteString(fmt.Sprint(slice.Index(i).Bool()))
+		case reflectTime:
+			buf.WriteString(slice.Index(i).Interface().(time.Time).Format(time.RFC3339))
+		default:
+			return fmt.Errorf("unsupported type '[]%s'", sliceOf)
+		}
+		buf.WriteString(delim)
+	}
+	key.SetValue(buf.String()[:buf.Len()-len(delim)])
+	return nil
+}
+
+// reflectWithProperType does the opposite thing as setWithProperType.
+func reflectWithProperType(t reflect.Type, key *Key, field reflect.Value, delim string, allowShadow bool) error {
+	switch t.Kind() {
+	case reflect.String:
+		key.SetValue(field.String())
+	case reflect.Bool:
+		key.SetValue(fmt.Sprint(field.Bool()))
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		key.SetValue(fmt.Sprint(field.Int()))
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		key.SetValue(fmt.Sprint(field.Uint()))
+	case reflect.Float32, reflect.Float64:
+		key.SetValue(fmt.Sprint(field.Float()))
+	case reflectTime:
+		key.SetValue(fmt.Sprint(field.Interface().(time.Time).Format(time.RFC3339)))
+	case reflect.Slice:
+		return reflectSliceWithProperType(key, field, delim, allowShadow)
+	case reflect.Ptr:
+		if !field.IsNil() {
+			return reflectWithProperType(t.Elem(), key, field.Elem(), delim, allowShadow)
+		}
+	default:
+		return fmt.Errorf("unsupported type %q", t)
+	}
+	return nil
+}
+
+// CR: copied from encoding/json/encode.go with modifications of time.Time support.
+// TODO: add more test coverage.
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	case reflectTime:
+		t, ok := v.Interface().(time.Time)
+		return ok && t.IsZero()
+	}
+	return false
+}
+
+// StructReflector is the interface implemented by struct types that can extract themselves into INI objects.
+type StructReflector interface {
+	ReflectINIStruct(*File) error
+}
+
+func (s *Section) reflectFrom(val reflect.Value) error {
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+	typ := val.Type()
+
+	for i := 0; i < typ.NumField(); i++ {
+		if !val.Field(i).CanInterface() {
+			continue
+		}
+
+		field := val.Field(i)
+		tpField := typ.Field(i)
+
+		tag := tpField.Tag.Get("ini")
+		if tag == "-" {
+			continue
+		}
+
+		rawName, omitEmpty, allowShadow, allowNonUnique, extends := parseTagOptions(tag)
+		if omitEmpty && isEmptyValue(field) {
+			continue
+		}
+
+		if r, ok := field.Interface().(StructReflector); ok {
+			return r.ReflectINIStruct(s.f)
+		}
+
+		fieldName := s.parseFieldName(tpField.Name, rawName)
+		if len(fieldName) == 0 || !field.CanSet() {
+			continue
+		}
+
+		if extends && tpField.Anonymous && (tpField.Type.Kind() == reflect.Ptr || tpField.Type.Kind() == reflect.Struct) {
+			if err := s.reflectFrom(field); err != nil {
+				return fmt.Errorf("reflect from field %q: %v", fieldName, err)
+			}
+			continue
+		}
+
+		if (tpField.Type.Kind() == reflect.Ptr && tpField.Type.Elem().Kind() == reflect.Struct) ||
+			(tpField.Type.Kind() == reflect.Struct && tpField.Type.Name() != "Time") {
+			// Note: The only error here is section doesn't exist.
+			sec, err := s.f.GetSection(fieldName)
+			if err != nil {
+				// Note: fieldName can never be empty here, ignore error.
+				sec, _ = s.f.NewSection(fieldName)
+			}
+
+			// Add comment from comment tag
+			if len(sec.Comment) == 0 {
+				sec.Comment = tpField.Tag.Get("comment")
+			}
+
+			if err = sec.reflectFrom(field); err != nil {
+				return fmt.Errorf("reflect from field %q: %v", fieldName, err)
+			}
+			continue
+		}
+
+		if allowNonUnique && tpField.Type.Kind() == reflect.Slice {
+			slice := field.Slice(0, field.Len())
+			if field.Len() == 0 {
+				return nil
+			}
+			sliceOf := field.Type().Elem().Kind()
+
+			for i := 0; i < field.Len(); i++ {
+				if sliceOf != reflect.Struct && sliceOf != reflect.Ptr {
+					return fmt.Errorf("field %q is not a slice of pointer or struct", fieldName)
+				}
+
+				sec, err := s.f.NewSection(fieldName)
+				if err != nil {
+					return err
+				}
+
+				// Add comment from comment tag
+				if len(sec.Comment) == 0 {
+					sec.Comment = tpField.Tag.Get("comment")
+				}
+
+				if err := sec.reflectFrom(slice.Index(i)); err != nil {
+					return fmt.Errorf("reflect from field %q: %v", fieldName, err)
+				}
+			}
+			continue
+		}
+
+		// Note: Same reason as section.
+		key, err := s.GetKey(fieldName)
+		if err != nil {
+			key, _ = s.NewKey(fieldName, "")
+		}
+
+		// Add comment from comment tag
+		if len(key.Comment) == 0 {
+			key.Comment = tpField.Tag.Get("comment")
+		}
+
+		delim := parseDelim(tpField.Tag.Get("delim"))
+		if err = reflectWithProperType(tpField.Type, key, field, delim, allowShadow); err != nil {
+			return fmt.Errorf("reflect field %q: %v", fieldName, err)
+		}
+
+	}
+	return nil
+}
+
+// ReflectFrom reflects section from given struct. It overwrites existing ones.
+func (s *Section) ReflectFrom(v interface{}) error {
+	typ := reflect.TypeOf(v)
+	val := reflect.ValueOf(v)
+
+	if s.name != DefaultSection && s.f.options.AllowNonUniqueSections &&
+		(typ.Kind() == reflect.Slice || typ.Kind() == reflect.Ptr) {
+		// Clear sections to make sure none exists before adding the new ones
+		s.f.DeleteSection(s.name)
+
+		if typ.Kind() == reflect.Ptr {
+			sec, err := s.f.NewSection(s.name)
+			if err != nil {
+				return err
+			}
+			return sec.reflectFrom(val.Elem())
+		}
+
+		slice := val.Slice(0, val.Len())
+		sliceOf := val.Type().Elem().Kind()
+		if sliceOf != reflect.Ptr {
+			return fmt.Errorf("not a slice of pointers")
+		}
+
+		for i := 0; i < slice.Len(); i++ {
+			sec, err := s.f.NewSection(s.name)
+			if err != nil {
+				return err
+			}
+
+			err = sec.reflectFrom(slice.Index(i))
+			if err != nil {
+				return fmt.Errorf("reflect from %dth field: %v", i, err)
+			}
+		}
+
+		return nil
+	}
+
+	if typ.Kind() == reflect.Ptr {
+		val = val.Elem()
+	} else {
+		return errors.New("not a pointer to a struct")
+	}
+
+	return s.reflectFrom(val)
+}
+
+// ReflectFrom reflects file from given struct.
+func (f *File) ReflectFrom(v interface{}) error {
+	return f.Section("").ReflectFrom(v)
+}
+
+// ReflectFromWithMapper reflects data sources from given struct with name mapper.
+func ReflectFromWithMapper(cfg *File, v interface{}, mapper NameMapper) error {
+	cfg.NameMapper = mapper
+	return cfg.ReflectFrom(v)
+}
+
+// ReflectFrom reflects data sources from given struct.
+func ReflectFrom(cfg *File, v interface{}) error {
+	return ReflectFromWithMapper(cfg, v, nil)
+}