Handle trailing comma in array

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/parsers/StringUtils.kt

@@ -82,6 +82,14 @@ internal fun String.trimCurlyBraces(): String = trimSymbols(this, "{", "}")
  */
 internal fun String.trimBrackets(): String = trimSymbols(this, "[", "]")
 
+/**
+ * If this string ends with comma(,) - will return the string with trailing comma removed.
+ * Otherwise, returns this string.
+ *
+ * @return string with the result
+ */
+internal fun String.removeTrailingComma(): String = this.removeSuffix(",")
+
 /**
  * If this string starts and end with a pair brackets([[]]) - will return the string with brackets removed
  * Otherwise, returns this string.

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/tree/nodes/pairs/values/TomlArray.kt

@@ -4,6 +4,7 @@ import com.akuleshov7.ktoml.TomlConfig
 import com.akuleshov7.ktoml.TomlInputConfig
 import com.akuleshov7.ktoml.TomlOutputConfig
 import com.akuleshov7.ktoml.exceptions.ParseException
+import com.akuleshov7.ktoml.parsers.removeTrailingComma
 import com.akuleshov7.ktoml.parsers.trimBrackets
 import com.akuleshov7.ktoml.tree.nodes.parseValue
 import com.akuleshov7.ktoml.writers.TomlEmitter
@@ -137,8 +138,9 @@ public class TomlArray internal constructor(
          */
         @Suppress("NESTED_BLOCK", "TOO_LONG_FUNCTION")
         private fun String.parseArray(): MutableList<String> {
+            val trimmed = trimBrackets().removeTrailingComma()
             // covering cases when the array is intentionally blank: myArray = []. It should be empty and not contain null
-            if (this.trimBrackets().isBlank()) {
+            if (trimmed.isBlank()) {
                 return mutableListOf()
             }
 
@@ -148,7 +150,6 @@ public class TomlArray internal constructor(
             var bufferBetweenCommas = StringBuilder()
             val result: MutableList<String> = mutableListOf()
 
-            val trimmed = trimBrackets()
             for (i in trimmed.indices) {
                 when (val current = trimmed[i]) {
                     '[' -> {

ktoml-core/src/commonTest/kotlin/com/akuleshov7/ktoml/decoders/ArrayDecoderTest.kt

@@ -15,6 +15,9 @@ import kotlin.test.assertTrue
 @Serializable
 data class SimpleArray(val a: List<Long>)
 
+@Serializable
+data class SimpleArrayWithNullableValues(val a: List<Long?>)
+
 @Serializable
 data class SimpleStringArray(val a: List<String>)
 
@@ -335,6 +338,21 @@ class SimpleArrayDecoderTest {
         assertEquals(SimpleArray(listOf(1, 2, 3)), Toml.decodeFromString(test))
     }
 
+    @Test
+    fun testArrayWithTrailingComma() {
+        var test = "a = [1, 2, 3,]"
+        assertEquals(SimpleArrayWithNullableValues(listOf(1, 2, 3)), Toml.decodeFromString(test))
+
+        test = """
+            a = [
+                1,
+                2,
+                3,
+            ]
+            """.trimIndent()
+        assertEquals(SimpleArrayWithNullableValues(listOf(1, 2, 3)), Toml.decodeFromString(test))
+    }
+
     @Test
     fun testSimpleArrayDecoderInNestedTable() {
         var test = """