CORDA-1670 fix multiple CorDapps for flow check (#3436)

* CORDA-1670 fix multiple CorDapps for flow check

* CORDA-1670 fix multiple CorDapps for flow check

* CORDA-1670 address code review comment

node/src/main/kotlin/net/corda/node/internal/NodeStartup.kt

@@ -15,6 +15,7 @@ import net.corda.node.NodeRegistrationOption
 import net.corda.node.SerialFilter
 import net.corda.node.VersionInfo
 import net.corda.node.defaultSerialFilter
+import net.corda.node.internal.cordapp.MultipleCordappsForFlowException
 import net.corda.node.services.config.NodeConfiguration
 import net.corda.node.services.config.NodeConfigurationImpl
 import net.corda.node.services.config.shouldStartLocalShell
@@ -135,6 +136,9 @@ open class NodeStartup(val args: Array<String>) {
         try {
             cmdlineOptions.baseDirectory.createDirectories()
             startNode(conf, versionInfo, startTime, cmdlineOptions)
+        } catch (e: MultipleCordappsForFlowException) {
+            logger.error(e.message)
+            return false
         } catch (e: CouldNotCreateDataSourceException) {
             logger.error(e.message, e.cause)
             return false

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

@@ -50,7 +50,7 @@ class CordappLoader private constructor(private val cordappJarPaths: List<Restri
         cordapps.flatMap { corDapp -> corDapp.allFlows.map { flow -> flow to corDapp } }
                 .groupBy { it.first }
                 .mapValues {
-                    require(it.value.size == 1) { "There are multiple CorDapp jars on the classpath for flow ${it.value.first().first.name}: ${it.value.map { it.second.name }.joinToString()}." }
+                    if(it.value.size > 1) { throw MultipleCordappsForFlowException("There are multiple CorDapp JARs on the classpath for flow ${it.value.first().first.name}: [ ${it.value.joinToString { it.second.name }} ].")  }
                     it.value.single().second
                 }
     }
@@ -363,3 +363,8 @@ class CordappLoader private constructor(private val cordappJarPaths: List<Restri
         }
     }
 }
+
+/**
+ * Thrown when scanning CorDapps.
+ */
+class MultipleCordappsForFlowException(message: String) : Exception(message)

node/src/main/kotlin/net/corda/node/internal/cordapp/CordappProviderImpl.kt

@@ -41,6 +41,9 @@ open class CordappProviderImpl(private val cordappLoader: CordappLoader,
 
     private fun verifyInstalledCordapps(attachmentStorage: AttachmentStorage) {
 
+        // This will invoke the lazy flowCordappMap property, thus triggering the MultipleCordappsForFlow check.
+        cordappLoader.flowCordappMap
+
         if (whitelistedContractImplementations.isEmpty()) {
             log.warn("The network parameters don't specify any whitelisted contract implementations. Please contact your zone operator. See https://docs.corda.net/network-map.html")
             return