Fix yml anchors/references when converting yml-to-json

Apparently they've started using Anchors and Aliases in yml files
upstream (see e.g. uk.yml -> male_first_name -> first_name).

Seems like jackson can't handle Anchors properly
(see FasterXML/jackson-dataformats-text#98)

As a workaround, we use snakeyaml to read .yml files to Map objects,
and then we use jackson to write them to .json files, since snakeyaml
seems to support anchors just fine without needing to jump through hoops.

buildSrc/build.gradle.kts

@@ -16,5 +16,6 @@ dependencies {
     implementation("com.adarshr:gradle-test-logger-plugin:4.0.0")
     // used by yaml-to-json buildSrc plugin
     implementation("com.fasterxml.jackson.core:jackson-databind:2.15.3")
-    implementation("com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:2.15.3")
+    // use snakeyaml instead of jackson-dataformat-yaml to properly handle yaml anchors and write them as actual values to json
+    implementation("org.yaml:snakeyaml:2.2")
 }

buildSrc/src/main/kotlin/yaml-to-json.gradle.kts

@@ -1,6 +1,5 @@
 import com.fasterxml.jackson.databind.ObjectMapper
-import com.fasterxml.jackson.dataformat.yaml.YAMLFactory
-import org.gradle.kotlin.dsl.create
+import org.yaml.snakeyaml.Yaml
 
 interface Yaml2JsonPluginExtension {
     val input: Property<File>
@@ -9,7 +8,13 @@ interface Yaml2JsonPluginExtension {
 
 class Yaml2JsonPlugin : Plugin<Project> {
     val jsonMapper = ObjectMapper()
-    val yamlMapper = ObjectMapper(YAMLFactory())
+    // https://github.com/FasterXML/jackson-dataformats-text/issues/98
+    /* We use snakeyaml since it can handle Anchors and References (Aliases) in yml files, which jackson can't apparently.
+     * We still can use jackson to write to json, because at that time,
+     * the Map we created from yaml will contain proper values and not simply anchor names,
+     * like it happens when using jackson to read yaml.
+     */
+    val yamlMapper = Yaml()
 
     override fun apply(p: Project) {
         val ext = p.extensions.create<Yaml2JsonPluginExtension>("yaml2jsonExt")
@@ -50,8 +55,7 @@ class Yaml2JsonPlugin : Plugin<Project> {
     }
 
     private fun writeYamlToJson(src: File, dest: File) {
-        val map = yamlMapper.readValue(src.inputStream(), Map::class.java)
+        val map = yamlMapper.loadAs(src.inputStream(), Map::class.java)
         jsonMapper.writeValue(dest, map)
     }
 }
-