fix(collect): from slice and map even if stream is nil

Author: sharpvik

filter_map.go

@@ -33,28 +33,13 @@ func FilterMap[I, O any](carry func(I) (O, bool)) StreamTransformer[I, O] {
 		_, ok = carry(item)
 		return
 	})
+
 	mapper := Map(func(item I) (mapped O) {
 		mapped, _ = carry(item)
 		return
 	})
+
 	return func(items Stream[I]) Stream[O] {
 		return mapper(filter(items))
 	}
 }
-
-type filterMap[I, O any] struct {
-	source Stream[I]
-	carry  func(I) (O, bool)
-}
-
-func (t *filterMap[I, O]) Next() (item O, err error) {
-	for {
-		var origin I
-		if origin, err = t.source.Next(); err != nil {
-			return
-		}
-		if item, ok := t.carry(origin); ok {
-			return item, nil
-		}
-	}
-}

hmap.go

@@ -11,16 +11,23 @@ func CollectMap[
 ](keyval func(T) (K, V)) StreamReducer[T, map[K]V] {
 	return func(items Stream[T]) (hmap map[K]V, err error) {
 		hmap = make(map[K]V)
+
+		if items == nil {
+			return
+		}
+
 		var item T
 		for err == nil {
 			if item, err = items.Next(); err == nil {
 				key, value := keyval(item)
 				hmap[key] = value
 			}
 		}
+
 		if err == io.EOF {
 			err = nil
 		}
+
 		return
 	}
 }

slice.go

@@ -13,15 +13,21 @@ func SliceStream[T any](items []T) Stream[T] {
 // end of this operation, io.EOF is not reported as this function is expected to
 // read stream until the end anyways.
 func CollectSlice[T any](items Stream[T]) (collected []T, err error) {
+	if items == nil {
+		return
+	}
+
 	var item T
 	for err == nil {
 		if item, err = items.Next(); err == nil {
 			collected = append(collected, item)
 		}
 	}
+
 	if err == io.EOF {
 		err = nil
 	}
+
 	return
 }
 

slice_test.go

@@ -0,0 +1,12 @@
+package fungi
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCollectSlice(t *testing.T) {
+	_, err := CollectSlice[int](nil)
+	assert.NoError(t, err)
+}