-
Notifications
You must be signed in to change notification settings - Fork 5
/
dto.go
437 lines (377 loc) · 10.8 KB
/
dto.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
// Package dto is an easy-to-use library for data mapping.
//
// dto maps primitives, structs, slices, maps, pointers
// and supports custom functions and error mapping.
//
// Contrary to other struct mappers it uses only name based field resolution
// and maps its values recursively. This means that go-dto tries to map struct fields
// with the same names.
//
// Conversion functions can be used to overwrite mapping behaviour.
// Inspection functions allow to modify a value after it has been mapped.
//
// See the tests and github page for more exmaples.
package dto
import (
"errors"
"fmt"
"reflect"
"strings"
)
type structValueMap = map[string]reflect.Value
// Marker type for functions with no receiver
type nilRecvT struct{}
var nilRecvRfType = reflect.TypeOf(nilRecvT{})
var errorRfType = reflect.TypeOf((*error)(nil)).Elem()
var mapperPtrRfType = reflect.TypeOf((*Mapper)(nil))
type convertFuncClosure = func(reflect.Value, *Mapper) (reflect.Value, error)
type inspectFuncClosure = func(reflect.Value, reflect.Value, *Mapper) error
const structTag = "dto"
// NoValidMappingError indicates that no valid mapping was found
type NoValidMappingError struct {
ToType reflect.Type
FromType reflect.Type
}
func (nvme NoValidMappingError) Error() string {
return fmt.Sprintf("No valid mapping found for %v from %v", nvme.ToType, nvme.FromType)
}
// Mapper contains conversion and inspect functions
type Mapper struct {
// linear search might be faster than nested maps
convFunc map[reflect.Type]map[reflect.Type]convertFuncClosure
postFunc map[reflect.Type]map[reflect.Type][]inspectFuncClosure
}
// ==================================== utils =================================
// Collect all struct fields (including anonymous) into a structValueMap
func collectStructFields(rfValue reflect.Value, rfType reflect.Type, fields structValueMap) {
for i := 0; i < rfType.NumField(); i++ {
fieldValue := rfValue.Field(i)
fieldType := rfType.Field(i)
if tags, ok := fieldType.Tag.Lookup(structTag); ok {
if strings.Contains(tags, "ignore") {
continue
}
}
if fieldType.Anonymous {
collectStructFields(fieldValue, fieldType.Type, fields)
} else {
fields[fieldType.Name] = fieldValue
}
}
}
// Return reflect.Value with pointer removed (first layer only)
func reflectValueRemovePtr(v interface{}) reflect.Value {
rv := reflect.ValueOf(v)
if rv.Type().Kind() == reflect.Ptr {
return rv.Elem()
}
return rv
}
// Maps an error from a reflect value
// Panics if the value is non nill and not an error
func errorFromReflectValue(rv reflect.Value) error {
if rv.IsNil() {
return nil
}
err, ok := rv.Interface().(error)
if !ok {
panic("Failed to map error from reflect.Value")
}
return err
}
// ==================================== Conversion and inspection functions ===
// Run inspect functions for (dst-src) pair
func (m *Mapper) runInspectFuncs(dstRv, srcRv reflect.Value) error {
toMap, ok := m.postFunc[dstRv.Type()]
if !ok {
return nil
}
for _, recvType := range []reflect.Type{srcRv.Type(), nilRecvRfType} {
funcs, ok := toMap[recvType]
if !ok {
continue
}
for _, fun := range funcs {
if err := fun(dstRv.Addr(), srcRv, m); err != nil {
return err
}
}
}
return nil
}
// Run convert function for (dst-src) pair
// Returns (error, true) if a valid function was found, (nil, false) otherwise
func (m *Mapper) runConvFuncs(dstRv, srcRv reflect.Value) (bool, error) {
toMap, ok := m.convFunc[srcRv.Type()]
if !ok {
return false, nil
}
if convertFunc, ok := toMap[dstRv.Type()]; ok {
val, err := convertFunc(srcRv, m)
if err != nil {
return true, err
}
dstRv.Set(val)
return true, nil
}
return false, nil
}
// HasCustomFuncs returns true if the Mapper has custom functions defined
func (m *Mapper) HasCustomFuncs() bool {
return len(m.convFunc)+len(m.postFunc) > 0
}
// AddConvFunc adds a conversion function to the Mapper
//
// Panics if f is not a valid conversion function
// Overwrites previous functions with the same type pair
func (m *Mapper) AddConvFunc(f interface{}) {
rt := reflect.TypeOf(f)
// check basic argument invariant
if rt.NumOut() < 1 || rt.NumIn() < 1 {
panic("Bad conversion function")
}
// check if to inject mapper
takesMapper := false
if rt.NumIn() > 1 && rt.In(1) == mapperPtrRfType {
takesMapper = true
}
// check if returns an error
returnsError := false
outType := rt.Out(0)
if rt.NumOut() > 1 && rt.Out(1).Implements(errorRfType) {
returnsError = true
}
inType := rt.In(0)
// create maps
if len(m.convFunc) == 0 {
m.convFunc = make(map[reflect.Type]map[reflect.Type]convertFuncClosure)
}
if len(m.convFunc[inType]) == 0 {
m.convFunc[inType] = make(map[reflect.Type]convertFuncClosure)
}
// register closure
m.convFunc[inType][outType] = func(from reflect.Value, m *Mapper) (reflect.Value, error) {
args := []reflect.Value{from}
if takesMapper {
args = append(args, reflect.ValueOf(m))
}
out := reflect.ValueOf(f).Call(args)
if returnsError {
return out[0], errorFromReflectValue(out[1])
}
return out[0], nil
}
}
// AddInspectFunc adds an inspection function to the Mapper
//
// Panics if f is not a valid inspection function
func (m *Mapper) AddInspectFunc(f interface{}) {
ft := reflect.TypeOf(f)
inType := ft.In(0).Elem()
// check if takes from
fromType := nilRecvRfType
if ft.NumIn() > 1 {
fromType = ft.In(1)
}
// check if takes mapper
takesMapper := false
if ft.NumIn() > 2 && ft.In(2) == reflect.TypeOf(m) {
takesMapper = true
}
// check if returns error
returnsError := false
if ft.NumOut() > 0 && ft.Out(0).Implements(errorRfType) {
returnsError = true
}
// create map path
if len(m.postFunc) == 0 {
m.postFunc = make(map[reflect.Type]map[reflect.Type][]inspectFuncClosure)
}
if len(m.postFunc[inType]) == 0 {
m.postFunc[inType] = make(map[reflect.Type][]inspectFuncClosure)
}
// register closure
m.postFunc[inType][fromType] = append(m.postFunc[inType][fromType],
func(v1, v2 reflect.Value, m *Mapper) error {
args := []reflect.Value{v1}
if fromType != nilRecvRfType {
args = append(args, v2)
}
if takesMapper {
args = append(args, reflect.ValueOf(m))
}
out := reflect.ValueOf(f).Call(args)
if returnsError {
return errorFromReflectValue(out[0])
}
return nil
},
)
}
// ==================================== Mapping functions =====================
// Map slices
// Panics if arguments are not slices
func (m *Mapper) mapSlice(toRv, fromRv reflect.Value) error {
toRv.Set(reflect.MakeSlice(toRv.Type(), fromRv.Len(), fromRv.Len()))
for i := 0; i < fromRv.Len(); i++ {
if err := m.mapValue(toRv.Index(i), fromRv.Index(i)); err != nil {
return err
}
}
return nil
}
// Map maps
// Panics if arguments are not maps
func (m *Mapper) mapMap(dstRv, srcRv reflect.Value) error {
dstRv.Set(reflect.MakeMapWithSize(dstRv.Type(), srcRv.Len()))
// Map values
mapIt := srcRv.MapRange()
for mapIt.Next() {
toKey := reflect.New(dstRv.Type().Key()).Elem()
toValue := reflect.New(dstRv.Type().Elem()).Elem()
if err := m.mapValue(toKey, mapIt.Key()); err != nil {
return err
}
if err := m.mapValue(toValue, mapIt.Value()); err != nil {
return err
}
dstRv.SetMapIndex(toKey, toValue)
}
return nil
}
// Map structs
// Panics if arguments are not structs
func (m *Mapper) mapStructs(dstRv, srcRv reflect.Value) error {
toFields := make(structValueMap)
collectStructFields(dstRv, dstRv.Type(), toFields)
fromFields := make(structValueMap)
collectStructFields(srcRv, srcRv.Type(), fromFields)
for fieldName, toValue := range toFields {
fromValue, ok := fromFields[fieldName]
if !ok {
continue
}
err := m.mapValue(toValue, fromValue)
if err != nil {
return err
}
}
return nil
}
// Map map values to slice
// Panics if arguments are not slice and map accordingly
func (m *Mapper) mapMapToSlice(dstRv, srcRv reflect.Value) error {
dstRv.Set(reflect.MakeSlice(dstRv.Type(), srcRv.Len(), srcRv.Len()))
i := 0
mapIt := srcRv.MapRange()
for mapIt.Next() {
if err := m.mapValue(dstRv.Index(i), mapIt.Value()); err != nil {
return err
}
i++
}
return nil
}
// Map a map of slices to slice
// Panics of arguments are not a map of slices and a slice accordingly
func (m *Mapper) mapMapSlicesToSlice(dstRv, srcRv reflect.Value) error {
// calculate length
sumLen := 0
mapIt := srcRv.MapRange()
for mapIt.Next() {
sumLen += mapIt.Value().Len()
}
dstRv.Set(reflect.MakeSlice(dstRv.Type(), sumLen, sumLen))
i := 0
mapIt = srcRv.MapRange()
for mapIt.Next() {
mapSlice := mapIt.Value()
for j := 0; j < mapSlice.Len(); i, j = i+1, j+1 {
if err := m.mapValue(dstRv.Index(i), mapSlice.Index(j)); err != nil {
return err
}
}
}
return nil
}
// Try to map any value
func (m *Mapper) mapValue(dstRv, srcRv reflect.Value) (returnError error) {
tk, fk := dstRv.Type().Kind(), srcRv.Type().Kind()
// Defer inspect functions
defer func() {
if returnError != nil {
return
}
returnError = m.runInspectFuncs(dstRv, srcRv)
}()
// 1. Check conversion functions
converted, err := m.runConvFuncs(dstRv, srcRv)
if converted {
return err
}
// 2. Check direct assignment
if srcRv.Type().AssignableTo(dstRv.Type()) {
dstRv.Set(srcRv)
return
}
// 3. Check conversion
if srcRv.Type().ConvertibleTo(dstRv.Type()) {
dstRv.Set(srcRv.Convert(dstRv.Type()))
return
}
// 4. Handle pointers by dereferencing from
if fk == reflect.Ptr {
// Skip null pointers
if srcRv.IsNil() {
return nil
}
return m.mapValue(dstRv, srcRv.Elem())
}
// 5. Handle pointers by dereferencing to
if tk == reflect.Ptr {
// Allocate new value if nil
if dstRv.IsNil() {
dstRv.Set(reflect.New(dstRv.Type().Elem()))
}
return m.mapValue(dstRv.Elem(), srcRv)
}
// 6. Handle sructs
if tk == reflect.Struct && fk == reflect.Struct {
return m.mapStructs(dstRv, srcRv)
}
// 7. Handle slices
if tk == reflect.Slice && fk == reflect.Slice {
return m.mapSlice(dstRv, srcRv)
}
// 8. Handle maps
if tk == reflect.Map && fk == reflect.Map {
return m.mapMap(dstRv, srcRv)
}
// 9. Handle map to slice
if tk == reflect.Slice && fk == reflect.Map {
err := m.mapMapToSlice(dstRv, srcRv)
// 9. Handle map of slices to slice
mapElemK := srcRv.Type().Elem().Kind()
if errors.As(err, &NoValidMappingError{}) && mapElemK == reflect.Slice {
// dont propagate errors
if errFlatten := m.mapMapSlicesToSlice(dstRv, srcRv); errFlatten == nil {
return
}
}
return err
}
return NoValidMappingError{
ToType: dstRv.Type(),
FromType: srcRv.Type(),
}
}
// ==================================== Public helpers ========================
// Map transfers values from src to dst
func (m *Mapper) Map(dst, src interface{}) error {
return m.mapValue(reflectValueRemovePtr(dst), reflectValueRemovePtr(src))
}
// Map transfers values from src to dst
func Map(dst, src interface{}) error {
m := Mapper{}
return m.Map(dst, src)
}