fix(codegen-kotlin): honor @isarray on entity/value fields → List<T>

KotlinEntityGenerator emitted a single (nullable) element type for array fields,
ignoring isArray — e.g. a field.object @objectref=Foo isArray:true became Foo?
instead of List<Foo>?. Wrap the resolved element type in List<T> when
field.isArrayType() (covers the isArray:true shorthand and a child @isarray attr);
nullability applies to the List, not the elements. Covers object refs and scalars.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dmealing

server/java/codegen-kotlin/src/main/kotlin/com/metaobjects/generator/kotlin/KotlinEntityGenerator.kt

@@ -11,7 +11,9 @@ import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.FileSpec
 import com.squareup.kotlinpoet.FunSpec
 import com.squareup.kotlinpoet.KModifier
+import com.squareup.kotlinpoet.LIST
 import com.squareup.kotlinpoet.ParameterSpec
+import com.squareup.kotlinpoet.ParameterizedTypeName.Companion.parameterizedBy
 import com.squareup.kotlinpoet.PropertySpec
 import com.squareup.kotlinpoet.TypeName
 import com.squareup.kotlinpoet.TypeSpec
@@ -181,6 +183,16 @@ class KotlinEntityGenerator : MultiFileDirectGeneratorBase<MetaObject>() {
      * not the in-memory shape.
      */
     private fun resolvePropertyType(field: MetaField<*>, owner: MetaObject, loader: MetaDataLoader): TypeName {
+        val element = resolveElementType(field, owner, loader)
+        // @isArray fields are a List of the element type (List<T>). isArrayType()
+        // covers both the `isArray: true` shorthand and a child @isArray attr.
+        // Nullable handling is applied by the caller to the List itself (List<T>?),
+        // not the elements — an array of non-null items.
+        return if (field.isArrayType) LIST.parameterizedBy(element) else element
+    }
+
+    /** The Kotlin TypeName for a single (non-array) element of [field]. */
+    private fun resolveElementType(field: MetaField<*>, owner: MetaObject, loader: MetaDataLoader): TypeName {
         // field.enum → typed enum class generated alongside this entity.
         KotlinTypeMapper.enumTypeName(field, owner)?.let { return it }
         if (field is ObjectField) {

server/java/codegen-kotlin/src/test/kotlin/com/metaobjects/generator/kotlin/KotlinEntityGeneratorTest.kt

@@ -88,6 +88,44 @@ class KotlinEntityGeneratorTest {
         }
     }
 
+    @Test fun isArrayFieldsEmitAsList() {
+        // @isArray on field.object → List<T>; on a scalar field → List<String>.
+        // Nullable handling applies to the List itself (List<T>? when not required;
+        // List<T> when required) — not to the elements.
+        val fx = """{
+          "metadata.root": { "package": "acme::demo", "children": [
+            { "object.value": { "name": "Tag", "children": [
+                { "field.string": { "name": "label", "@required": true } }
+            ] } },
+            { "object.value": { "name": "Post", "children": [
+                { "field.object": { "name": "tags",
+                    "@objectRef": "Tag", "isArray": true } },
+                { "field.string": { "name": "aliases", "isArray": true, "@required": true } }
+            ] } }
+          ] }
+        }""".trimIndent()
+
+        val outDir = Files.createTempDirectory("kgen-arr-")
+        try {
+            val gen = KotlinEntityGenerator()
+            gen.setArgs(mapOf("outputDir" to outDir.toString()))
+            gen.execute(loadString("arr", fx))
+
+            val postSrc = Files.readString(outDir.resolve("acme/demo/Post.kt"))
+            // object array, not required → List<Tag>? = null
+            assertTrue("val tags: List<Tag>? = null" in postSrc,
+                "expected `val tags: List<Tag>? = null` in:\n$postSrc")
+            // scalar array, required → List<String> (non-null)
+            assertTrue("val aliases: List<String>" in postSrc,
+                "expected `val aliases: List<String>` in:\n$postSrc")
+            // must NOT collapse an array to a single element
+            assertFalse("val tags: Tag" in postSrc,
+                "array field must not emit a single element type:\n$postSrc")
+        } finally {
+            outDir.toFile().deleteRecursively()
+        }
+    }
+
     // === field.enum coverage ===============================================
 
     private val enumFixture = """{