Fix range error for Array.slice

core/variant/array.cpp

@@ -454,17 +454,21 @@ Array Array::slice(int p_begin, int p_end, int p_step, bool p_deep) const {
 
  const int s = size();
 
- int begin = CLAMP(p_begin, -s, s);
+ if (s == 0 || (p_begin < -s && p_step < 0) || (p_begin >= s && p_step > 0)) {
+ return result;
+ }
+
+ int begin = CLAMP(p_begin, -s, s - 1);
  if (begin < 0) {
  begin += s;
  }
- int end = CLAMP(p_end, -s, s);
+ int end = CLAMP(p_end, -s - 1, s);
  if (end < 0) {
  end += s;
  }
 
- ERR_FAIL_COND_V_MSG(p_step > 0 && begin > end, result, "Slice is positive, but bounds is decreasing.");
- ERR_FAIL_COND_V_MSG(p_step < 0 && begin < end, result, "Slice is negative, but bounds is increasing.");
+ ERR_FAIL_COND_V_MSG(p_step > 0 && begin > end, result, "Slice step is positive, but bounds are decreasing.");
+ ERR_FAIL_COND_V_MSG(p_step < 0 && begin < end, result, "Slice step is negative, but bounds are increasing.");
 
  int result_size = (end - begin) / p_step + (((end - begin) % p_step != 0) ? 1 : 0);
  result.resize(result_size);

doc/classes/Array.xml

@@ -584,6 +584,7 @@
  If either [param begin] or [param end] are negative, they will be relative to the end of the array (i.e. [code]arr.slice(0, -2)[/code] is a shorthand for [code]arr.slice(0, arr.size() - 2)[/code]).
  If specified, [param step] is the relative index between source elements. It can be negative, then [param begin] must be higher than [param end]. For example, [code][0, 1, 2, 3, 4, 5].slice(5, 1, -2)[/code] returns [code][5, 3][/code].
  If [param deep] is true, each element will be copied by value rather than by reference.
+ [b]Note:[/b] To include the first element when [param step] is negative, use [code]arr.slice(begin, -arr.size() - 1, step)[/code] (i.e. [code][0, 1, 2].slice(1, -4, -1)[/code] returns [code][1, 0][/code]).
  </description>
  </method>
  <method name="sort">

tests/core/variant/test_array.h

@@ -304,13 +304,31 @@ TEST_CASE("[Array] slice()") {
  CHECK(slice8[1] == Variant(3));
  CHECK(slice8[2] == Variant(1));
 
+ Array slice9 = array.slice(10, 0, -2);
+ CHECK(slice9.size() == 3);
+ CHECK(slice9[0] == Variant(5));
+ CHECK(slice9[1] == Variant(3));
+ CHECK(slice9[2] == Variant(1));
+
+ Array slice10 = array.slice(2, -10, -1);
+ CHECK(slice10.size() == 3);
+ CHECK(slice10[0] == Variant(2));
+ CHECK(slice10[1] == Variant(1));
+ CHECK(slice10[2] == Variant(0));
+
  ERR_PRINT_OFF;
- Array slice9 = array.slice(4, 1);
- CHECK(slice9.size() == 0);
+ Array slice11 = array.slice(4, 1);
+ CHECK(slice11.size() == 0);
 
- Array slice10 = array.slice(3, -4);
- CHECK(slice10.size() == 0);
+ Array slice12 = array.slice(3, -4);
+ CHECK(slice12.size() == 0);
  ERR_PRINT_ON;
+
+ Array slice13 = Array().slice(1);
+ CHECK(slice13.size() == 0);
+
+ Array slice14 = array.slice(6);
+ CHECK(slice14.size() == 0);
 }
 
 TEST_CASE("[Array] Duplicate array") {