Update Kotlin to 2.0 (#900)

- update Kotlin from 1.7.10 to 2.0.21
  - Kotlin 1.6 dependencies in Gradle lock files are expected because kotlinc,
    which is also used by some tests, internally uses some 1.6 dependencies
    for backwards compatibility reasons.
- update kotlinx-html and kotlinx-serialization
- adapt Kotlin code where necessary
- use Kotlin stdlib Path APIs where possible
- fix IntelliJ Kotlin inspection warnings
- reformat code with `./gradlew spotlessApply`
  - ktfmt adds lots of trailing commas
- Add workaround to fix IntelliJ "unresolved reference" errors

pkl-config-kotlin/src/main/kotlin/org/pkl/config/kotlin/ConfigExtensions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,14 +38,15 @@ import org.pkl.config.kotlin.mapper.KotlinConverterFactories
  */
 inline fun <reified T> Config.to(): T {
   val javaType = object : JavaType<T>() {}
-  val result = `as`<T>(javaType.type)
+  // `as T?` may no longer be required after switching to JSpecify
+  val result = `as`<T>(javaType.type) as T?
   if (result == null && null !is T) {
     throw ConversionException(
       "Expected a non-null value but got `null`. " +
         "To allow null values, convert to a nullable Kotlin type, for example `String?`."
     )
   }
-  return result
+  return result as T
 }
 
 /**

pkl-config-kotlin/src/test/kotlin/org/pkl/config/kotlin/ConfigExtensionsTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -171,7 +171,7 @@ class ConfigExtensionsTest {
         mapOf(
           "l" to SimplePerson("lilly"),
           "b" to SimplePerson("bob"),
-          "s" to SimplePerson("susan")
+          "s" to SimplePerson("susan"),
         )
       )
   }
@@ -189,14 +189,14 @@ class ConfigExtensionsTest {
         mapOf(
           "l" to SimplePerson("lilly"),
           "b" to SimplePerson("bob"),
-          "s" to SimplePerson("susan")
+          "s" to SimplePerson("susan"),
         )
       )
   }
 
   @Test
   fun `convert enum with mangled names`() {
-    val values = MangledNameEnum.values().map { "\"$it\"" }
+    val values = MangledNameEnum.entries.map { "\"$it\"" }
     val config =
       evaluator.evaluate(
         text(
@@ -208,7 +208,7 @@ class ConfigExtensionsTest {
         )
       )
     val allEnumValues = config["allEnumValues"].to<Set<MangledNameEnum>>()
-    assertThat(allEnumValues).isEqualTo(MangledNameEnum.values().toSet())
+    assertThat(allEnumValues).isEqualTo(MangledNameEnum.entries.toSet())
   }
 
   data class SimplePerson(val name: String)
@@ -218,7 +218,7 @@ class ConfigExtensionsTest {
   enum class Hobby {
     SWIMMING,
     @Suppress("unused") SURFING,
-    READING
+    READING,
   }
 
   data class Address<out T>(val street: T)
@@ -240,7 +240,7 @@ class ConfigExtensionsTest {
   class PersonWithDefaults(
     val name: String = "Pigeon",
     val age: Int = 42,
-    val hobbies: List<String>
+    val hobbies: List<String>,
   )
 
   @Suppress("NonAsciiCharacters", "EnumEntryName")
@@ -252,6 +252,6 @@ class ConfigExtensionsTest {
     _42_FROM_INVALID_START("42-from-invalid-start"),
     __EMOJI__("❎Emoji✅✅"),
     ÀŒÜ("àœü"),
-    日本_つくば("日本-つくば")
+    日本_つくば("日本-つくば"),
   }
 }

pkl-config-kotlin/src/test/kotlin/org/pkl/config/kotlin/mapper/KotlinConversionsTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,19 +42,19 @@ class KotlinConversionsTest {
 
   @Test
   fun pIntToULong() {
-    assertThat(KotlinConversions.pIntToULong.converter.convert(0, mapper)).isEqualTo(0UL)
+    assertThat(KotlinConversions.pIntToULong.converter.convert(0L, mapper)).isEqualTo(0UL)
 
     assertThat(KotlinConversions.pIntToULong.converter.convert(Long.MAX_VALUE, mapper))
       .isEqualTo(Long.MAX_VALUE.toULong())
 
     assertThrows<ConversionException> {
-      KotlinConversions.pIntToULong.converter.convert(-1, mapper)
+      KotlinConversions.pIntToULong.converter.convert(-1L, mapper)
     }
   }
 
   @Test
   fun pIntToUInt() {
-    assertThat(KotlinConversions.pIntToUInt.converter.convert(0, mapper)).isEqualTo(0u)
+    assertThat(KotlinConversions.pIntToUInt.converter.convert(0L, mapper)).isEqualTo(0u)
 
     assertThat(KotlinConversions.pIntToUInt.converter.convert(UInt.MAX_VALUE.toLong(), mapper))
       .isEqualTo(UInt.MAX_VALUE)
@@ -63,12 +63,14 @@ class KotlinConversionsTest {
       KotlinConversions.pIntToUInt.converter.convert(UInt.MAX_VALUE.toLong() + 1, mapper)
     }
 
-    assertThrows<ConversionException> { KotlinConversions.pIntToUInt.converter.convert(-1, mapper) }
+    assertThrows<ConversionException> {
+      KotlinConversions.pIntToUInt.converter.convert(-1L, mapper)
+    }
   }
 
   @Test
   fun pIntToUShort() {
-    assertThat(KotlinConversions.pIntToUShort.converter.convert(0, mapper)).isEqualTo(0.toUShort())
+    assertThat(KotlinConversions.pIntToUShort.converter.convert(0L, mapper)).isEqualTo(0.toUShort())
 
     assertThat(KotlinConversions.pIntToUShort.converter.convert(UShort.MAX_VALUE.toLong(), mapper))
       .isEqualTo(UShort.MAX_VALUE)
@@ -78,7 +80,7 @@ class KotlinConversionsTest {
     }
 
     assertThrows<ConversionException> {
-      KotlinConversions.pIntToUShort.converter.convert(-1, mapper)
+      KotlinConversions.pIntToUShort.converter.convert(-1L, mapper)
     }
   }
 }