fixed "Concept not found" exception when a concept is not generated by api-gen

The model may contain more concepts than what is used
in the Kotlin project.
Often you have expression like this:
rootNodes.filterIsInstances<N_MyConcept>
Then the missing concept are not required and the exception
doesn't indicate an actual problem.

Author: slisson

metamodel-runtime/src/commonMain/kotlin/org/modelix/metamodel/TypedLanguagesRegistry.kt

@@ -3,6 +3,7 @@ package org.modelix.metamodel
 import org.modelix.model.api.ILanguageRepository
 import org.modelix.model.api.INode
 import org.modelix.model.api.resolve
+import org.modelix.model.api.tryResolve
 import kotlin.jvm.JvmName
 import kotlin.reflect.KClass
 import kotlin.reflect.cast
@@ -36,8 +37,8 @@ object TypedLanguagesRegistry : ILanguageRepository {
     }
 
     fun wrapNode(node: INode): ITypedNode {
-        val concept = (node.getConceptReference()?.resolve() as? GeneratedConcept<*, *>)
-            ?: throw IllegalArgumentException("Unknown concept: ${node.getConceptReference()}")
+        val concept = (node.getConceptReference()?.tryResolve() as? GeneratedConcept<*, *>)
+            ?: return UnknownConceptInstance(node)
         return concept.wrap(node)
     }
 }

metamodel-runtime/src/commonMain/kotlin/org/modelix/metamodel/UnknownConcept.kt

@@ -0,0 +1,90 @@
+package org.modelix.metamodel
+
+import org.modelix.model.api.IChildLink
+import org.modelix.model.api.IConcept
+import org.modelix.model.api.IConceptReference
+import org.modelix.model.api.ILanguage
+import org.modelix.model.api.INode
+import org.modelix.model.api.IProperty
+import org.modelix.model.api.IReferenceLink
+import org.modelix.model.area.IArea
+
+abstract class EmptyConcept : IConcept {
+    override fun isAbstract(): Boolean = true
+
+    override fun isSubConceptOf(superConcept: IConcept?): Boolean = superConcept == this
+
+    override fun getDirectSuperConcepts(): List<IConcept> = emptyList()
+
+    override fun isExactly(concept: IConcept?): Boolean = concept == this
+
+    override fun getOwnProperties(): List<IProperty> = emptyList()
+
+    override fun getOwnChildLinks(): List<IChildLink> = emptyList()
+
+    override fun getOwnReferenceLinks(): List<IReferenceLink> = emptyList()
+
+    override fun getAllProperties(): List<IProperty> = emptyList()
+
+    override fun getAllChildLinks(): List<IChildLink> = emptyList()
+
+    override fun getAllReferenceLinks(): List<IReferenceLink> = emptyList()
+
+    override fun getProperty(name: String): IProperty {
+        throw IllegalArgumentException("Cannot get property '$name'. No concept information available for '${getUID()}'.")
+    }
+
+    override fun getChildLink(name: String): IChildLink {
+        throw IllegalArgumentException("Cannot get link '$name'. No concept information available for '${getUID()}'.")
+    }
+
+    override fun getReferenceLink(name: String): IReferenceLink {
+        throw IllegalArgumentException("Cannot get link '$name'. No concept information available for '${getUID()}'.")
+    }
+}
+
+object NullConcept : EmptyConcept(), IConceptReference {
+    override fun getReference(): IConceptReference = this
+
+    override val language: ILanguage?
+        get() = null
+
+    override fun getUID(): String = "null"
+
+    override fun getShortName(): String = "null"
+
+    override fun getLongName(): String = getShortName()
+
+    override fun resolve(area: IArea?): IConcept? {
+        return this
+    }
+
+    override fun serialize(): String = "null"
+}
+
+data class UnknownConcept(private val ref: IConceptReference) : EmptyConcept() {
+    override fun getReference(): IConceptReference {
+        return ref
+    }
+
+    override val language: ILanguage?
+        get() = null
+
+    override fun getUID(): String = ref.getUID()
+
+    override fun getShortName(): String = "Unknown[${ref.getUID()}]"
+
+    override fun getLongName(): String = getShortName()
+}
+
+data class UnknownTypedConcept(private val ref: IConceptReference?) : ITypedConcept {
+    override val _concept: IConcept
+        get() = ref?.let { UnknownConcept(it) } ?: NullConcept
+}
+
+data class UnknownConceptInstance(val node: INode) : ITypedNode {
+    override val _concept: ITypedConcept
+        get() = UnknownTypedConcept(node.getConceptReference())
+
+    override fun unwrap(): INode = node
+}

model-api/src/commonMain/kotlin/org/modelix/model/api/IConceptReference.kt

@@ -47,3 +47,4 @@ interface IConceptReference {
 }
 
 fun IConceptReference.resolve(): IConcept = ILanguageRepository.resolveConcept(this)
+fun IConceptReference.tryResolve(): IConcept? = ILanguageRepository.tryResolveConcept(this)

model-api/src/commonMain/kotlin/org/modelix/model/api/ILanguageRepository.kt

@@ -6,11 +6,12 @@ interface ILanguageRepository {
         private var repositories: Set<ILanguageRepository> = setOf(DefaultLanguageRepository)
 
         fun resolveConcept(ref: IConceptReference): IConcept {
+            return tryResolveConcept(ref) ?: throw RuntimeException("Concept not found: $ref")
+        }
+        fun tryResolveConcept(ref: IConceptReference): IConcept? {
             val concepts = repositories.mapNotNull { it.resolveConcept(ref.getUID()) }
             return when (concepts.size) {
-                0 -> {
-                    throw RuntimeException("Concept not found: $ref")
-                }
+                0 -> null
                 1 -> concepts.first()
                 else -> throw RuntimeException("Multiple concepts found for $ref: $concepts")
             }