Allow return of errors from Value func

enumerable/concat.go

@@ -34,7 +34,7 @@ func (s *enumerableConcat[T]) Next() (bool, error) {
 	}
 }
 
-func (s *enumerableConcat[T]) Value() T {
+func (s *enumerableConcat[T]) Value() (T, error) {
 	return s.sources[s.currentSourceIndex].Value()
 }
 

enumerable/enumerable.go

@@ -20,7 +20,7 @@ type Enumerable[T any] interface {
 	//
 	// If the previous Next call did not return true, or Next has never been called
 	// the behaviour and return value of this function is undefined.
-	Value() T
+	Value() (T, error)
 
 	// Reset resets the enumerable, allowing for re-iteration.
 	Reset()
@@ -49,8 +49,8 @@ func (s *enumerableSlice[T]) Next() (bool, error) {
 	return true, nil
 }
 
-func (s *enumerableSlice[T]) Value() T {
-	return s.source[s.currentIndex]
+func (s *enumerableSlice[T]) Value() (T, error) {
+	return s.source[s.currentIndex], nil
 }
 
 func (s *enumerableSlice[T]) Reset() {
@@ -68,7 +68,10 @@ func ForEach[T any](source Enumerable[T], action func(item T)) error {
 		if !hasNext {
 			break
 		}
-		item := source.Value()
+		item, err := source.Value()
+		if err != nil {
+			return err
+		}
 		action(item)
 	}
 	source.Reset()
@@ -101,5 +104,11 @@ func TryGetFirst[T any](source Enumerable[T]) (T, bool, error) {
 		var defaultV T
 		return defaultV, false, err
 	}
-	return source.Value(), true, nil
+
+	val, err := source.Value()
+	if err != nil {
+		var defaultV T
+		return defaultV, false, err
+	}
+	return val, true, nil
 }

enumerable/select.go

@@ -25,7 +25,11 @@ func (s *enumerableSelect[TSource, TResult]) Next() (bool, error) {
 		return hasNext, err
 	}
 
-	value := s.source.Value()
+	value, err := s.source.Value()
+	if err != nil {
+		return false, nil
+	}
+
 	// We do this here to keep the work (and errors) in the `Next` call
 	result, err := s.selector(value)
 	if err != nil {
@@ -36,8 +40,8 @@ func (s *enumerableSelect[TSource, TResult]) Next() (bool, error) {
 	return true, nil
 }
 
-func (s *enumerableSelect[TSource, TResult]) Value() TResult {
-	return s.currentValue
+func (s *enumerableSelect[TSource, TResult]) Value() (TResult, error) {
+	return s.currentValue, nil
 }
 
 func (s *enumerableSelect[TSource, TResult]) Reset() {

enumerable/skip.go

@@ -28,7 +28,7 @@ func (s *enumerableSkip[T]) Next() (bool, error) {
 	return s.source.Next()
 }
 
-func (s *enumerableSkip[T]) Value() T {
+func (s *enumerableSkip[T]) Value() (T, error) {
 	return s.source.Value()
 }
 

enumerable/sort.go

@@ -27,10 +27,14 @@ func Sort[T any](source Enumerable[T], less func(T, T) bool, capacity int) Enume
 func (s *enumerableSort[T]) Next() (bool, error) {
 	if s.result == nil {
 		result := make([]T, 0, s.capacity)
+		var searchErr error
+
 		// Declaring an anonymous function costs, so we do it here outside of the loop
 		// even though it is slightly less intuitive
 		f := func(i int) bool {
-			return !s.less(result[i], s.source.Value())
+			var val T
+			val, searchErr = s.source.Value()
+			return !s.less(result[i], val)
 		}
 
 		for i := 0; i <= s.capacity; i++ {
@@ -44,7 +48,12 @@ func (s *enumerableSort[T]) Next() (bool, error) {
 
 			previousLength := len(result)
 			indexOfFirstGreaterValue := sort.Search(previousLength, f)
-			value := s.source.Value()
+			if searchErr != nil {
+				// This is quite ugly, but sort.Search does not allow for anything else
+				return false, searchErr
+			}
+
+			value, err := s.source.Value()
 			result = append(result, value)
 			if indexOfFirstGreaterValue == previousLength {
 				// Value is the greatest, and belongs at the end
@@ -63,7 +72,7 @@ func (s *enumerableSort[T]) Next() (bool, error) {
 	return s.result.Next()
 }
 
-func (s *enumerableSort[T]) Value() T {
+func (s *enumerableSort[T]) Value() (T, error) {
 	return s.result.Value()
 }
 

enumerable/take.go

@@ -23,7 +23,7 @@ func (s *enumerableTake[T]) Next() (bool, error) {
 	return s.source.Next()
 }
 
-func (s *enumerableTake[T]) Value() T {
+func (s *enumerableTake[T]) Value() (T, error) {
 	return s.source.Value()
 }
 

enumerable/where.go

@@ -22,14 +22,18 @@ func (s *enumerableWhere[T]) Next() (bool, error) {
 			return hasNext, err
 		}
 
-		value := s.source.Value()
+		value, err := s.source.Value()
+		if err != nil {
+			return false, err
+		}
+
 		if passes, err := s.predicate(value); passes || err != nil {
 			return passes, err
 		}
 	}
 }
 
-func (s *enumerableWhere[T]) Value() T {
+func (s *enumerableWhere[T]) Value() (T, error) {
 	return s.source.Value()
 }