v0.0.162

goextVersion.go

@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.157"
+const GoextVersion = "0.0.162"
 
-const GoextVersionTimestamp = "2023-06-10T16:22:14+0200"
+const GoextVersionTimestamp = "2023-06-11T16:38:47+0200"

mongoext/registry.go

@@ -16,6 +16,9 @@ func CreateGoExtBsonRegistry() *bsoncodec.Registry {
 	rb.RegisterTypeDecoder(reflect.TypeOf(rfctime.RFC3339NanoTime{}), rfctime.RFC3339NanoTime{})
 	rb.RegisterTypeDecoder(reflect.TypeOf(&rfctime.RFC3339NanoTime{}), rfctime.RFC3339NanoTime{})
 
+	rb.RegisterTypeDecoder(reflect.TypeOf(rfctime.Date{}), rfctime.Date{})
+	rb.RegisterTypeDecoder(reflect.TypeOf(&rfctime.Date{}), rfctime.Date{})
+
 	bsoncodec.DefaultValueEncoders{}.RegisterDefaultEncoders(rb)
 	bsoncodec.DefaultValueDecoders{}.RegisterDefaultDecoders(rb)
 

rfctime/date.go

@@ -0,0 +1,240 @@
+package rfctime
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/bson/bsoncodec"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"reflect"
+	"time"
+)
+
+type Date struct {
+	Year  int
+	Month int
+	Day   int
+}
+
+func (t Date) Time(loc *time.Location) time.Time {
+	return time.Date(t.Year, time.Month(t.Month), t.Day, 0, 0, 0, 0, loc)
+}
+
+func (t Date) TimeUTC() time.Time {
+	return time.Date(t.Year, time.Month(t.Month), t.Day, 0, 0, 0, 0, time.UTC)
+}
+
+func (t Date) TimeLocal() time.Time {
+	return time.Date(t.Year, time.Month(t.Month), t.Day, 0, 0, 0, 0, time.Local)
+}
+
+func (t Date) MarshalBinary() ([]byte, error) {
+	return t.TimeUTC().MarshalBinary()
+}
+
+func (t *Date) UnmarshalBinary(data []byte) error {
+	nt := time.Time{}
+	if err := nt.UnmarshalBinary(data); err != nil {
+		return err
+	}
+	t.Year = nt.Year()
+	t.Month = int(nt.Month())
+	t.Day = nt.Day()
+	return nil
+}
+
+func (t Date) GobEncode() ([]byte, error) {
+	return t.TimeUTC().GobEncode()
+}
+
+func (t *Date) GobDecode(data []byte) error {
+	nt := time.Time{}
+	if err := nt.GobDecode(data); err != nil {
+		return err
+	}
+	t.Year = nt.Year()
+	t.Month = int(nt.Month())
+	t.Day = nt.Day()
+	return nil
+}
+
+func (t *Date) UnmarshalJSON(data []byte) error {
+	str := ""
+	if err := json.Unmarshal(data, &str); err != nil {
+		return err
+	}
+	t0, err := time.Parse(t.FormatStr(), str)
+	if err != nil {
+		return err
+	}
+	t.Year = t0.Year()
+	t.Month = int(t0.Month())
+	t.Day = t0.Day()
+	return nil
+}
+
+func (t Date) MarshalJSON() ([]byte, error) {
+	str := t.TimeUTC().Format(t.FormatStr())
+	return json.Marshal(str)
+}
+
+func (t Date) MarshalText() ([]byte, error) {
+	b := make([]byte, 0, len(t.FormatStr()))
+	return t.TimeUTC().AppendFormat(b, t.FormatStr()), nil
+}
+
+func (t *Date) UnmarshalText(data []byte) error {
+	var err error
+	v, err := time.Parse(t.FormatStr(), string(data))
+	if err != nil {
+		return err
+	}
+	t.Year = v.Year()
+	t.Month = int(v.Month())
+	t.Day = v.Day()
+	return nil
+}
+
+func (t *Date) UnmarshalBSONValue(bt bsontype.Type, data []byte) error {
+	if bt == bsontype.Null {
+		// we can't set nil in UnmarshalBSONValue (so we use default(struct))
+		// Use mongoext.CreateGoExtBsonRegistry if you need to unmarsh pointer values
+		// https://stackoverflow.com/questions/75167597
+		// https://jira.mongodb.org/browse/GODRIVER-2252
+		*t = Date{}
+		return nil
+	}
+	if bt != bsontype.String {
+		return errors.New(fmt.Sprintf("cannot unmarshal %v into Date", bt))
+	}
+
+	var tt string
+	err := bson.RawValue{Type: bt, Value: data}.Unmarshal(&tt)
+	if err != nil {
+		return err
+	}
+
+	v, err := time.Parse(t.FormatStr(), tt)
+	if err != nil {
+		return err
+	}
+	t.Year = v.Year()
+	t.Month = int(v.Month())
+	t.Day = v.Day()
+
+	return nil
+}
+
+func (t Date) MarshalBSONValue() (bsontype.Type, []byte, error) {
+	return bson.MarshalValue(t.TimeUTC().Format(t.FormatStr()))
+}
+
+func (t Date) DecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if val.Kind() == reflect.Ptr && val.IsNil() {
+		if !val.CanSet() {
+			return errors.New("ValueUnmarshalerDecodeValue")
+		}
+		val.Set(reflect.New(val.Type().Elem()))
+	}
+
+	tp, src, err := bsonrw.Copier{}.CopyValueToBytes(vr)
+	if err != nil {
+		return err
+	}
+
+	if val.Kind() == reflect.Ptr && len(src) == 0 {
+		val.Set(reflect.Zero(val.Type()))
+		return nil
+	}
+
+	err = t.UnmarshalBSONValue(tp, src)
+	if err != nil {
+		return err
+	}
+
+	if val.Kind() == reflect.Ptr {
+		val.Set(reflect.ValueOf(&t))
+	} else {
+		val.Set(reflect.ValueOf(t))
+	}
+
+	return nil
+}
+
+func (t Date) Serialize() string {
+	return t.TimeUTC().Format(t.FormatStr())
+}
+
+func (t Date) FormatStr() string {
+	return "2006-01-02"
+}
+
+func (t Date) Date() (year int, month time.Month, day int) {
+	return t.TimeUTC().Date()
+}
+
+func (t Date) Weekday() time.Weekday {
+	return t.TimeUTC().Weekday()
+}
+
+func (t Date) ISOWeek() (year, week int) {
+	return t.TimeUTC().ISOWeek()
+}
+
+func (t Date) YearDay() int {
+	return t.TimeUTC().YearDay()
+}
+
+func (t Date) AddDate(years int, months int, days int) Date {
+	return NewDate(t.TimeUTC().AddDate(years, months, days))
+}
+
+func (t Date) Unix() int64 {
+	return t.TimeUTC().Unix()
+}
+
+func (t Date) UnixMilli() int64 {
+	return t.TimeUTC().UnixMilli()
+}
+
+func (t Date) UnixMicro() int64 {
+	return t.TimeUTC().UnixMicro()
+}
+
+func (t Date) UnixNano() int64 {
+	return t.TimeUTC().UnixNano()
+}
+
+func (t Date) Format(layout string) string {
+	return t.TimeUTC().Format(layout)
+}
+
+func (t Date) GoString() string {
+	return t.TimeUTC().GoString()
+}
+
+func (t Date) String() string {
+	return t.TimeUTC().String()
+}
+
+func NewDate(t time.Time) Date {
+	return Date{
+		Year:  t.Year(),
+		Month: int(t.Month()),
+		Day:   t.Day(),
+	}
+}
+
+func NowDate(loc *time.Location) Date {
+	return NewDate(time.Now().In(loc))
+}
+
+func NowDateLoc() Date {
+	return NewDate(time.Now().In(time.UTC))
+}
+
+func NowDateUTC() Date {
+	return NewDate(time.Now().In(time.Local))
+}

wmo/collection.go

@@ -27,7 +27,7 @@ type Cursorable interface {
 	Next(ctx context.Context) bool
 }
 
-type fullTypeRef[TData any] struct {
+type fullTypeRef struct {
 	IsPointer      bool
 	Kind           reflect.Kind
 	RealType       reflect.Type
@@ -38,9 +38,11 @@ type fullTypeRef[TData any] struct {
 }
 
 type Coll[TData any] struct {
-	coll          *mongo.Collection
+	coll                *mongo.Collection                                        // internal mongo collection, access via Collection()
-	dataTypeMap   map[string]fullTypeRef[TData]
+	dataTypeMap         map[string]fullTypeRef                                   // list of TData fields (only if TData is not an interface)
-	customDecoder *func(ctx context.Context, dec Decodable) (TData, error)
+	implDataTypeMap     map[reflect.Type]map[string]fullTypeRef                  // dynamic list of fields of TData implementations (only if TData is an interface)
+	customDecoder       *func(ctx context.Context, dec Decodable) (TData, error) // custom decoding function (useful if TData is an interface)
+	isInterfaceDataType bool                                                     // true if TData is an interface (not a struct)
 }
 
 func (c *Coll[TData]) Collection() *mongo.Collection {
@@ -51,7 +53,10 @@ func (c *Coll[TData]) Name() string {
 	return c.coll.Name()
 }
 
-func (c *Coll[TData]) WithDecodeFunc(cdf func(ctx context.Context, dec Decodable) (TData, error)) *Coll[TData] {
+func (c *Coll[TData]) WithDecodeFunc(cdf func(ctx context.Context, dec Decodable) (TData, error), example TData) *Coll[TData] {
+
+	c.EnsureInitializedReflection(example)
+
 	c.customDecoder = langext.Ptr(cdf)
 	return c
 }

wmo/queryAggregate.go

@@ -19,3 +19,20 @@ func (c *Coll[TData]) Aggregate(ctx context.Context, pipeline mongo.Pipeline, op
 
 	return res, nil
 }
+
+func (c *Coll[TData]) AggregateOneOpt(ctx context.Context, pipeline mongo.Pipeline, opts ...*options.AggregateOptions) (*TData, error) {
+	cursor, err := c.coll.Aggregate(ctx, pipeline, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	if cursor.Next(ctx) {
+		v, err := c.decodeSingle(ctx, cursor)
+		if err != nil {
+			return nil, err
+		}
+		return &v, nil
+	}
+
+	return nil, nil
+}

wmo/queryList.go

@@ -62,6 +62,8 @@ func (c *Coll[TData]) List(ctx context.Context, filter ct.Filter, pageSize *int,
 
 	last := entities[len(entities)-1]
 
+	c.EnsureInitializedReflection(last)
+
 	nextToken, err := c.createToken(sortPrimary, sortDirPrimary, sortSecondary, sortDirSecondary, last, pageSize)
 	if err != nil {
 		return nil, ct.CursorToken{}, err

wmo/reflection.go

@@ -1,25 +1,62 @@
 package wmo
 
 import (
+	"errors"
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
 	"gogs.mikescher.com/BlackForestBytes/goext/reflectext"
 	"reflect"
 	"strings"
 )
 
-func (c *Coll[TData]) init() {
+func (c *Coll[TData]) EnsureInitializedReflection(v TData) {
 
-	c.dataTypeMap = make(map[string]fullTypeRef[TData])
+	if !c.isInterfaceDataType {
+		return // only dynamically load dataTypeMap on interface TData
+	}
+
+	rval := reflect.ValueOf(v)
+	for rval.Type().Kind() == reflect.Pointer {
+		rval = rval.Elem()
+	}
+
+	if _, ok := c.implDataTypeMap[rval.Type()]; ok {
+		return // already loaded
+	}
+
+	m := make(map[string]fullTypeRef)
+
+	c.initFields("", rval, m, make([]int, 0))
+
+	c.implDataTypeMap[rval.Type()] = m
+}
+
+func (c *Coll[TData]) init() {
 
 	example := *new(TData)
 
-	v := reflect.ValueOf(example)
+	datatype := reflect.TypeOf(&example).Elem()
 
-	c.initFields("", v, make([]int, 0))
+	if datatype.Kind() == reflect.Interface {
+
+		c.isInterfaceDataType = true
+
+		c.dataTypeMap = make(map[string]fullTypeRef)
+		c.implDataTypeMap = make(map[reflect.Type]map[string]fullTypeRef)
+	} else {
+
+		c.isInterfaceDataType = false
+
+		c.dataTypeMap = make(map[string]fullTypeRef)
+		c.implDataTypeMap = make(map[reflect.Type]map[string]fullTypeRef)
+
+		v := reflect.ValueOf(example)
+		c.initFields("", v, c.dataTypeMap, make([]int, 0))
+
+	}
 
 }
 
-func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, idxarr []int) {
+func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, m map[string]fullTypeRef, idxarr []int) {
 
 	rtyp := rval.Type()
 
@@ -32,25 +69,38 @@ func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, idxarr []int
 			continue
 		}
 
+		bsontags := make([]string, 0)
 		bsonkey, found := rsfield.Tag.Lookup("bson")
 		if !found {
 			continue
 		}
 		if strings.Contains(bsonkey, ",") {
+			bsontags = strings.Split(bsonkey[strings.Index(bsonkey, ",")+1:], ",")
 			bsonkey = bsonkey[:strings.Index(bsonkey, ",")]
 		}
 		if bsonkey == "-" {
 			continue
 		}
 
+		if bsonkey == "" {
+			bsonkey = rsfield.Name
+		}
+
 		fullKey := prefix + bsonkey
 
 		newIdxArr := langext.ArrCopy(idxarr)
 		newIdxArr = append(newIdxArr, i)
 
+		if langext.InArray("inline", bsontags) && rvfield.Kind() == reflect.Struct {
+
+			// pass-through field
+			c.initFields(prefix, rvfield, m, newIdxArr)
+
+		} else {
+
 			if rvfield.Type().Kind() == reflect.Pointer {
 
-			c.dataTypeMap[fullKey] = fullTypeRef[TData]{
+				m[fullKey] = fullTypeRef{
 					IsPointer:      true,
 					RealType:       rvfield.Type(),
 					Kind:           rvfield.Type().Elem().Kind(),
@@ -62,7 +112,7 @@ func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, idxarr []int
 
 			} else {
 
-			c.dataTypeMap[fullKey] = fullTypeRef[TData]{
+				m[fullKey] = fullTypeRef{
 					IsPointer:      false,
 					RealType:       rvfield.Type(),
 					Kind:           rvfield.Type().Kind(),
@@ -75,7 +125,9 @@ func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, idxarr []int
 			}
 
 			if rvfield.Kind() == reflect.Struct {
-			c.initFields(fullKey+".", rvfield, newIdxArr)
+				c.initFields(fullKey+".", rvfield, m, newIdxArr)
+			}
+
 		}
 
 	}
@@ -84,7 +136,10 @@ func (c *Coll[TData]) initFields(prefix string, rval reflect.Value, idxarr []int
 
 func (c *Coll[TData]) getTokenValueAsMongoType(value string, fieldName string) (any, error) {
 
-	fref := c.dataTypeMap[fieldName]
+	fref, err := c.getFieldType(fieldName)
+	if err != nil {
+		return nil, err
+	}
 
 	pss := reflectext.PrimitiveStringSerializer{}
 
@@ -94,7 +149,10 @@ func (c *Coll[TData]) getTokenValueAsMongoType(value string, fieldName string) (
 
 func (c *Coll[TData]) getFieldValueAsTokenString(entity TData, fieldName string) (string, error) {
 
-	realValue := c.getFieldValue(entity, fieldName)
+	realValue, err := c.getFieldValue(entity, fieldName)
+	if err != nil {
+		return "", err
+	}
 
 	pss := reflectext.PrimitiveStringSerializer{}
 
@@ -102,12 +160,56 @@ func (c *Coll[TData]) getFieldValueAsTokenString(entity TData, fieldName string)
 
 }
 
-func (c *Coll[TData]) getFieldType(fieldName string) fullTypeRef[TData] {
+func (c *Coll[TData]) getFieldType(fieldName string) (fullTypeRef, error) {
-	return c.dataTypeMap[fieldName]
+	if c.isInterfaceDataType {
+
+		for _, m := range c.implDataTypeMap {
+			if r, ok := m[fieldName]; ok {
+				return r, nil
+			}
+		}
+
+		return fullTypeRef{}, errors.New("unknown field: '" + fieldName + "' (in any impl)")
+
+	} else {
+
+		if r, ok := c.dataTypeMap[fieldName]; ok {
+			return r, nil
+		} else {
+			return fullTypeRef{}, errors.New("unknown field: '" + fieldName + "'")
+		}
+
+	}
+
 }
 
-func (c *Coll[TData]) getFieldValue(data TData, fieldName string) any {
+func (c *Coll[TData]) getFieldValue(data TData, fieldName string) (any, error) {
-	fref := c.dataTypeMap[fieldName]
+	if c.isInterfaceDataType {
+
 		rval := reflect.ValueOf(data)
-	return rval.FieldByIndex(fref.Index).Interface()
+		for rval.Type().Kind() == reflect.Pointer {
+			rval = rval.Elem()
+		}
+
+		if m, ok := c.implDataTypeMap[rval.Type()]; ok {
+			if fref, ok := m[fieldName]; ok {
+				rval := reflect.ValueOf(data)
+				return rval.FieldByIndex(fref.Index).Interface(), nil
+			} else {
+				return nil, errors.New("unknown bson field '" + fieldName + "' in type '" + rval.Type().String() + "'")
+			}
+		} else {
+			return nil, errors.New("unknown TData type: '" + rval.Type().String() + "'")
+		}
+
+	} else {
+
+		if fref, ok := c.dataTypeMap[fieldName]; ok {
+			rval := reflect.ValueOf(data)
+			return rval.FieldByIndex(fref.Index).Interface(), nil
+		} else {
+			return nil, errors.New("unknown bson field '" + fieldName + "'")
+		}
+
+	}
 }

wmo/reflection_test.go

@@ -1,11 +1,14 @@
 package wmo
 
 import (
+	"context"
+	"go.mongodb.org/mongo-driver/bson/primitive"
 	"go.mongodb.org/mongo-driver/mongo"
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
 	"gogs.mikescher.com/BlackForestBytes/goext/rfctime"
 	"gogs.mikescher.com/BlackForestBytes/goext/timeext"
 	"gogs.mikescher.com/BlackForestBytes/goext/tst"
+	"reflect"
 	"testing"
 	"time"
 )
@@ -45,35 +48,51 @@ func TestReflectionGetFieldType(t *testing.T) {
 		MDate: t1,
 	}
 
-	tst.AssertEqual(t, coll.getFieldType("_id").Kind.String(), "string")
+	gft := func(k string) fullTypeRef {
-	tst.AssertEqual(t, coll.getFieldType("_id").Type.String(), "wmo.IDType")
+		v, err := coll.getFieldType(k)
-	tst.AssertEqual(t, coll.getFieldType("_id").Name, "ID")
+		if err != nil {
-	tst.AssertEqual(t, coll.getFieldType("_id").IsPointer, false)
+			t.Errorf("%s: %v", "failed to getFieldType", err)
-	tst.AssertEqual(t, coll.getFieldValue(d, "_id").(IDType), "1")
+		}
+		return v
+	}
 
-	tst.AssertEqual(t, coll.getFieldType("cdate").Kind.String(), "struct")
+	gfv := func(k string) any {
-	tst.AssertEqual(t, coll.getFieldType("cdate").Type.String(), "time.Time")
+		v, err := coll.getFieldValue(d, k)
-	tst.AssertEqual(t, coll.getFieldType("cdate").Name, "CDate")
+		if err != nil {
-	tst.AssertEqual(t, coll.getFieldType("cdate").IsPointer, false)
+			t.Errorf("%s: %v", "failed to getFieldType", err)
-	tst.AssertEqual(t, coll.getFieldValue(d, "cdate").(time.Time), t0)
+		}
+		return v
+	}
 
-	tst.AssertEqual(t, coll.getFieldType("sub.a").Kind.String(), "string")
+	tst.AssertEqual(t, gft("_id").Kind.String(), "string")
-	tst.AssertEqual(t, coll.getFieldType("sub.a").Type.String(), "string")
+	tst.AssertEqual(t, gft("_id").Type.String(), "wmo.IDType")
-	tst.AssertEqual(t, coll.getFieldType("sub.a").Name, "A")
+	tst.AssertEqual(t, gft("_id").Name, "ID")
-	tst.AssertEqual(t, coll.getFieldType("sub.a").IsPointer, false)
+	tst.AssertEqual(t, gft("_id").IsPointer, false)
-	tst.AssertEqual(t, coll.getFieldValue(d, "sub.a").(string), "2")
+	tst.AssertEqual(t, gfv("_id").(IDType), "1")
 
-	tst.AssertEqual(t, coll.getFieldType("str").Kind.String(), "string")
+	tst.AssertEqual(t, gft("cdate").Kind.String(), "struct")
-	tst.AssertEqual(t, coll.getFieldType("str").Type.String(), "string")
+	tst.AssertEqual(t, gft("cdate").Type.String(), "time.Time")
-	tst.AssertEqual(t, coll.getFieldType("str").Name, "Str")
+	tst.AssertEqual(t, gft("cdate").Name, "CDate")
-	tst.AssertEqual(t, coll.getFieldType("str").IsPointer, false)
+	tst.AssertEqual(t, gft("cdate").IsPointer, false)
-	tst.AssertEqual(t, coll.getFieldValue(d, "str").(string), "3")
+	tst.AssertEqual(t, gfv("cdate").(time.Time), t0)
 
-	tst.AssertEqual(t, coll.getFieldType("ptr").Kind.String(), "int")
+	tst.AssertEqual(t, gft("sub.a").Kind.String(), "string")
-	tst.AssertEqual(t, coll.getFieldType("ptr").Type.String(), "int")
+	tst.AssertEqual(t, gft("sub.a").Type.String(), "string")
-	tst.AssertEqual(t, coll.getFieldType("ptr").Name, "Ptr")
+	tst.AssertEqual(t, gft("sub.a").Name, "A")
-	tst.AssertEqual(t, coll.getFieldType("ptr").IsPointer, true)
+	tst.AssertEqual(t, gft("sub.a").IsPointer, false)
-	tst.AssertEqual(t, *coll.getFieldValue(d, "ptr").(*int), 4)
+	tst.AssertEqual(t, gfv("sub.a").(string), "2")
+
+	tst.AssertEqual(t, gft("str").Kind.String(), "string")
+	tst.AssertEqual(t, gft("str").Type.String(), "string")
+	tst.AssertEqual(t, gft("str").Name, "Str")
+	tst.AssertEqual(t, gft("str").IsPointer, false)
+	tst.AssertEqual(t, gfv("str").(string), "3")
+
+	tst.AssertEqual(t, gft("ptr").Kind.String(), "int")
+	tst.AssertEqual(t, gft("ptr").Type.String(), "int")
+	tst.AssertEqual(t, gft("ptr").Name, "Ptr")
+	tst.AssertEqual(t, gft("ptr").IsPointer, true)
+	tst.AssertEqual(t, *gfv("ptr").(*int), 4)
 }
 
 func TestReflectionGetTokenValueAsMongoType(t *testing.T) {
@@ -177,3 +196,31 @@ func TestReflectionGetFieldValueAsTokenString(t *testing.T) {
 	tst.AssertEqual(t, gfvats(d, "cdate"), t0.Format(time.RFC3339Nano))
 	tst.AssertEqual(t, gfvats(d, "mdate"), t0.Format(time.RFC3339Nano))
 }
+
+func TestReflectionWithInterface(t *testing.T) {
+
+	type TestData struct {
+		ID    primitive.ObjectID `bson:"_id"`
+		CDate time.Time          `bson:"cdate"`
+	}
+
+	type TestInterface interface {
+	}
+
+	coll1 := W[TestInterface](&mongo.Collection{})
+
+	tst.AssertTrue(t, coll1.coll != nil)
+	tst.AssertEqual(t, 0, len(coll1.implDataTypeMap))
+
+	df := func(ctx context.Context, dec Decodable) (TestInterface, error) {
+		return TestData{}, nil
+	}
+
+	coll2 := W[TestInterface](&mongo.Collection{}).WithDecodeFunc(df, TestData{})
+
+	tst.AssertTrue(t, coll2.coll != nil)
+	tst.AssertEqual(t, 1, len(coll2.implDataTypeMap))
+
+	tst.AssertEqual(t, "ID", coll2.implDataTypeMap[reflect.TypeOf(TestData{})]["_id"].Name)
+	tst.AssertEqual(t, "CDate", coll2.implDataTypeMap[reflect.TypeOf(TestData{})]["cdate"].Name)
+}