[CORDA-2636] Ensure states created with contract upgrades can be migrated (#4786)

* Ensure states created with contract upgrades can be migrated

* Remove line from api-current.txt representing an uncallable constructor

node-api/src/main/kotlin/net/corda/nodeapi/internal/cordapp/CordappLoader.kt

@@ -0,0 +1,33 @@
+package net.corda.nodeapi.internal.cordapp
+
+import net.corda.core.cordapp.Cordapp
+import net.corda.core.flows.FlowLogic
+import net.corda.core.internal.cordapp.CordappImpl
+import net.corda.core.schemas.MappedSchema
+
+/**
+ * Handles loading [Cordapp]s.
+ */
+interface CordappLoader : AutoCloseable {
+
+    /**
+     * Returns all [Cordapp]s found.
+     */
+    val cordapps: List<CordappImpl>
+
+    /**
+     * Returns a [ClassLoader] containing all types from all [Cordapp]s.
+     */
+    val appClassLoader: ClassLoader
+
+    /**
+     * Returns a map between flow class and owning [Cordapp].
+     * The mappings are unique, and the node will not start otherwise.
+     */
+    val flowCordappMap: Map<Class<out FlowLogic<*>>, Cordapp>
+
+    /**
+     * Returns all [MappedSchema] found inside the [Cordapp]s.
+     */
+    val cordappSchemas: Set<MappedSchema>
+}

node-api/src/main/kotlin/net/corda/nodeapi/internal/persistence/SchemaMigration.kt

@@ -12,6 +12,7 @@ import net.corda.core.identity.CordaX500Name
 import net.corda.nodeapi.internal.MigrationHelpers.getMigrationResource
 import net.corda.core.schemas.MappedSchema
 import net.corda.core.utilities.contextLogger
+import net.corda.nodeapi.internal.cordapp.CordappLoader
 import sun.security.x509.X500Name
 import java.io.ByteArrayInputStream
 import java.io.InputStream
@@ -28,7 +29,7 @@ class SchemaMigration(
         val schemas: Set<MappedSchema>,
         val dataSource: DataSource,
         private val databaseConfig: DatabaseConfig,
-        private val classLoader: ClassLoader = Thread.currentThread().contextClassLoader,
+        cordappLoader: CordappLoader? = null,
         private val currentDirectory: Path?,
         private val ourName: CordaX500Name) {
 
@@ -36,8 +37,15 @@ class SchemaMigration(
         private val logger = contextLogger()
         const val NODE_BASE_DIR_KEY = "liquibase.nodeDaseDir"
         const val NODE_X500_NAME = "liquibase.nodeName"
+        val loader = ThreadLocal<CordappLoader>()
     }
 
+    init {
+        loader.set(cordappLoader)
+    }
+
+    private val classLoader = cordappLoader?.appClassLoader ?: Thread.currentThread().contextClassLoader
+
     /**
      * Main entry point to the schema migration.
      * Called during node startup.

node-api/src/test/kotlin/net/corda/nodeapi/internal/AttachmentsClassLoaderStaticContractTests.kt

@@ -16,7 +16,7 @@ import net.corda.core.serialization.deserialize
 import net.corda.core.serialization.serialize
 import net.corda.core.transactions.LedgerTransaction
 import net.corda.core.transactions.TransactionBuilder
-import net.corda.node.cordapp.CordappLoader
+import net.corda.nodeapi.internal.cordapp.CordappLoader
 import net.corda.node.internal.cordapp.CordappProviderImpl
 import net.corda.node.internal.cordapp.JarScanningCordappLoader
 import net.corda.nodeapi.internal.AttachmentsClassLoaderStaticContractTests.AttachmentDummyContract.Companion.ATTACHMENT_PROGRAM_ID