feat(model-api-gen): default concepts for setChild and addChild

If the child concept is not abstract it will be used as the default.

Author: mhuster23

model-api-gen-gradle-test/kotlin-generation/src/test/kotlin/org/modelix/modelql/typed/TypedModelQLTest.kt

@@ -26,6 +26,10 @@ import jetbrains.mps.baseLanguage.C_StaticMethodDeclaration
 import jetbrains.mps.baseLanguage.C_VariableReference
 import jetbrains.mps.baseLanguage.ClassConcept
 import jetbrains.mps.baseLanguage.StaticMethodDeclaration
+import jetbrains.mps.core.xml.C_XmlComment
+import jetbrains.mps.core.xml.C_XmlCommentLine
+import jetbrains.mps.core.xml.C_XmlDocument
+import jetbrains.mps.core.xml.C_XmlFile
 import jetbrains.mps.lang.editor.imageGen.C_ImageGenerator
 import jetbrains.mps.lang.editor.imageGen.ImageGenerator
 import org.modelix.apigen.test.ApigenTestLanguages
@@ -131,6 +135,12 @@ class TypedModelQLTest {
             rootNode.addNewChild("imageGen", -1, C_ImageGenerator.untyped())
                 .typed<ImageGenerator>()
                 .apply { node = cls1 }
+
+            // Example for single non-abstract child
+            rootNode.addNewChild("xmlFile", -1, C_XmlFile.untyped())
+
+            // Example for mulitple non-abstract child
+            rootNode.addNewChild("xmlComment", -1, C_XmlComment.untyped())
         }
     }
 
@@ -370,4 +380,22 @@ class TypedModelQLTest {
         assertNotNull(actual)
         assertTrue(actual.instanceOf(C_MinusExpression))
     }
+
+    @Test
+    fun `set child - default concept`() = runTest { httpClient ->
+        val client = ModelQLClient.builder().url("http://localhost/query").httpClient(httpClient).build()
+        client.query { root ->
+            root.descendants().ofConcept(C_XmlFile)
+                .first()
+                .setDocument()
+        }
+
+        val actual = client.query { root ->
+            root.descendants().ofConcept(C_XmlFile)
+                .first()
+                .document
+        }
+
+        assertTrue { actual.instanceOf(C_XmlDocument) }
+    }
 }

model-api-gen/src/main/kotlin/org/modelix/metamodel/generator/MetaModelGenerator.kt

@@ -466,12 +466,18 @@ class MetaModelGenerator(
                             )
                             val returnType = IMonoStep::class.asTypeName().parameterizedBy(targetType)
                             val receiverType = IMonoStep::class.asTypeName().parameterizedBy(concept.nodeWrapperInterfaceType())
+                            val conceptParameter = ParameterSpec.builder("concept", ITypedConcept::class.asTypeName()).apply {
+                                if (!feature.type.resolved.abstract) {
+                                    defaultValue("%T", feature.type.resolved.conceptWrapperInterfaceClass())
+                                }
+                            }.build()
+
                             if (feature.multiple) {
                                 addFunction(
                                     FunSpec.builder(feature.adderMethodName())
                                         .returns(returnType)
                                         .receiver(receiverType)
-                                        .addParameter("concept", ITypedConcept::class.asTypeName())
+                                        .addParameter(conceptParameter)
                                         .addParameter(
                                             ParameterSpec.builder("index", Int::class.asTypeName())
                                                 .defaultValue("-1")
@@ -490,7 +496,7 @@ class MetaModelGenerator(
                                     FunSpec.builder(feature.setterName())
                                         .returns(returnType)
                                         .receiver(receiverType)
-                                        .addParameter("concept", ITypedConcept::class.asTypeName())
+                                        .addParameter(conceptParameter)
                                         .addStatement(
                                             "return %T.setChild(this, %T.%N, concept)",
                                             TypedModelQL::class.asTypeName(),