Fix the handling of list index

stof · stof · commit 5b57452bd432 · 2021-05-05T22:29:52.000+02:00
diff --git a/src/Compiler.php b/src/Compiler.php
@@ -8548,32 +8548,48 @@ protected function libListSeparator($args)
     protected static $libNth = ['list', 'n'];
     protected function libNth($args)
     {
-        $list = $this->coerceList($args[0], ',', false);
-        $n = $this->assertNumber($args[1])->getDimension();
+        $list = $this->coerceList($args[0]);
+        $n = $this->assertInteger($args[1], 'n');
+
+        if ($n === 0) {
+            throw SassScriptException::forArgument('List index may not be 0.', 'n');
+        }
+
+        $listLength = \count($list[2]);
+
+        if (abs($n) > $listLength) {
+            throw SassScriptException::forArgument("Invalid index $n for a list with $listLength elements.", 'n');
+        }
 
         if ($n > 0) {
             $n--;
-        } elseif ($n < 0) {
-            $n += \count($list[2]);
+        } else {
+            $n += $listLength;
         }
 
-        return isset($list[2][$n]) ? $list[2][$n] : static::$defaultValue;
+        return $list[2][$n];
     }
 
     protected static $libSetNth = ['list', 'n', 'value'];
     protected function libSetNth($args)
     {
         $list = $this->coerceList($args[0]);
-        $n = $this->assertNumber($args[1])->getDimension();
+        $n = $this->assertInteger($args[1], 'n');
 
-        if ($n > 0) {
-            $n--;
-        } elseif ($n < 0) {
-            $n += \count($list[2]);
+        if ($n === 0) {
+            throw SassScriptException::forArgument('List index may not be 0.', 'n');
+        }
+
+        $listLength = \count($list[2]);
+
+        if (abs($n) > $listLength) {
+            throw SassScriptException::forArgument("Invalid index $n for a list with $listLength elements.", 'n');
         }
 
-        if (! isset($list[2][$n])) {
-            throw $this->error('Invalid argument for "n"');
+        if ($n > 0) {
+            $n--;
+        } else {
+            $n += $listLength;
         }
 
         $list[2][$n] = $args[2];
diff --git a/tests/specs/sass-spec-exclude.txt b/tests/specs/sass-spec-exclude.txt
@@ -225,11 +225,7 @@ core_functions/list/join/multi/map/second/space
 core_functions/list/join/single/both/comma/last
 core_functions/list/join/single/first/undecided/and_comma
 core_functions/list/join/single/non_list/first/comma
-core_functions/list/nth/error/index/0
-core_functions/list/nth/error/index/too_high
-core_functions/list/nth/error/index/too_low
 core_functions/list/separator/empty/comma
-core_functions/list/set_nth/error/index/0
 core_functions/list/utils/empty_map/same_as_empty_list
 core_functions/list/utils/real_separator/empty/comma
 core_functions/list/utils/real_separator/empty/undecided
