Support loading YAML files containing anchors/references

This allows anchors and references to be used in all configuration
files. The implementation is a workaround for jackson-dataformats-text
bug #98:
FasterXML/jackson-dataformats-text#98

src/main/kotlin/db/AbstractFileRegistry.kt

@@ -7,6 +7,7 @@ import io.vertx.core.Vertx
 import io.vertx.kotlin.core.executeBlockingAwait
 import io.vertx.kotlin.core.file.readFileAwait
 import org.apache.sshd.common.util.io.DirectoryScanner
+import org.yaml.snakeyaml.Yaml
 import java.io.File
 import java.nio.file.Path
 
@@ -51,7 +52,12 @@ abstract class AbstractFileRegistry {
       if (file.toLowerCase().endsWith(".json")) {
         JsonUtils.mapper.readValue(content, tr)
       } else {
-        YamlUtils.mapper.readValue(content, tr)
+        // Use SnakeYML to parse file and then Jackson to convert it to an
+        // object. This is a workaround for jackson-dataformats-text bug #98:
+        // https://github.com/FasterXML/jackson-dataformats-text/issues/98
+        val yaml = Yaml()
+        val l = yaml.load<List<Any>>(content)
+        YamlUtils.mapper.convertValue(l, tr)
       }
     }
   }

src/test/kotlin/db/MetadataRegistryTest.kt

@@ -0,0 +1,40 @@
+package db
+
+import io.vertx.core.Vertx
+import io.vertx.junit5.VertxExtension
+import io.vertx.junit5.VertxTestContext
+import io.vertx.kotlin.coroutines.dispatcher
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.launch
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+
+/**
+ * Tests for [MetadataRegistry]
+ * @author Michel Kraemer
+ */
+@ExtendWith(VertxExtension::class)
+class MetadataRegistryTest {
+  /**
+   * Test if a YAML file with references can be loaded
+   */
+  @Test
+  fun yamlWithReferences(vertx: Vertx, ctx: VertxTestContext) {
+    val registry = FileMetadataRegistry(listOf("src/test/resources/db/services_with_references.yaml"), vertx)
+
+    GlobalScope.launch(vertx.dispatcher()) {
+      val services = registry.findServices()
+      assertThat(services).hasSize(2)
+      val s1 = services[0]
+      val s2 = services[1]
+      assertThat(s1.id).isEqualTo("service1")
+      assertThat(s2.id).isEqualTo("service2")
+      assertThat(s1.path).isEqualTo("service.sh")
+      assertThat(s2.path).isEqualTo(s1.path)
+      assertThat(s2.runtime).isEqualTo(s1.runtime)
+      assertThat(s2.parameters).isEmpty()
+      ctx.completeNow()
+    }
+  }
+}

src/test/resources/db/services_with_references.yaml

@@ -0,0 +1,13 @@
+- id: service1
+  name: Service 1
+  description: My first service
+  path: &mypath "service.sh"
+  runtime: &myruntime other
+  parameters: &myparams []
+
+- id: service2
+  name: Service 2
+  description: My second service
+  path: *mypath
+  runtime: *myruntime
+  parameters: *myparams