slice: make Chunks return its input on n == 0

slice/slice.go

@@ -255,11 +255,12 @@ func Coalesce[T comparable](vs ...T) T {
 // have length exactly n; the last may have fewer. The slices returned share
 // storage with the input.
 //
-// Chunks will panic if n ≤ 0.
+// Chunks will panic if n < 0. If n == 0, Batches returns a single chunk
+// containing the entire input.
 func Chunks[T any, Slice ~[]T](vs Slice, n int) []Slice {
-	if n <= 0 {
+	if n < 0 {
 		panic("max must be positive")
-	} else if n >= len(vs) {
+	} else if n == 0 || n >= len(vs) {
 		return []Slice{vs}
 	}
 	out := make([]Slice, 0, (len(vs)+n-1)/n)

slice/slice_test.go

@@ -334,12 +334,15 @@ func TestChunks(t *testing.T) {
 		want  [][]string
 	}{
 		// An empty slice has only one covering.
+		{"", 0, [][]string{{}}},
 		{"", 1, [][]string{{}}},
 		{"", 5, [][]string{{}}},
 
+		{"x", 0, [][]string{{"x"}}},
 		{"x", 1, [][]string{{"x"}}},
 		{"x", 2, [][]string{{"x"}}},
 
+		{"a b c d e", 0, [][]string{{"a", "b", "c", "d", "e"}}},
 		{"a b c d e", 1, [][]string{{"a"}, {"b"}, {"c"}, {"d"}, {"e"}}},
 		{"a b c d e", 2, [][]string{{"a", "b"}, {"c", "d"}, {"e"}}},
 		{"a b c d e", 3, [][]string{{"a", "b", "c"}, {"d", "e"}}},
@@ -359,7 +362,6 @@ func TestChunks(t *testing.T) {
 		}
 	}
 
-	t.Logf("OK n=0: %v", mtest.MustPanic(t, func() { slice.Chunks([]string{"a"}, 0) }))
 	t.Logf("OK n<0: %v", mtest.MustPanic(t, func() { slice.Chunks([]string{"a"}, -1) }))
 }