swap dataformat-yaml with snakeyaml (elastic#15599) (elastic#15606)

This removes the dependency on jackson's dataformat-yaml. Since there's only a single place where this library is used in core: to load the plugin alias definition, the code can be replaced by the underlying snakeyaml.

Co-authored-by: Andrea Selva <[email protected]>
(cherry picked from commit 93d8a9d)

Co-authored-by: João Duarte <[email protected]>

logstash-core/build.gradle

@@ -215,7 +215,7 @@ dependencies {
     api "com.fasterxml.jackson.core:jackson-annotations:${jacksonVersion}"
     implementation 'org.codehaus.janino:janino:3.1.0'
     implementation "com.fasterxml.jackson.dataformat:jackson-dataformat-cbor:${jacksonVersion}"
-    implementation "com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:${jacksonVersion}"
+    implementation group: 'org.yaml', name: 'snakeyaml', version: '2.2'
     implementation group: 'com.google.guava', name: 'guava', version: '32.1.2-jre'
     implementation('com.google.googlejavaformat:google-java-format:1.15.0') {
         exclude group: 'com.google.guava', module: 'guava'

logstash-core/src/main/java/org/logstash/plugins/AliasRegistry.java

@@ -1,12 +1,10 @@
 package org.logstash.plugins;
 
-import com.fasterxml.jackson.core.type.TypeReference;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 import org.apache.commons.codec.digest.DigestUtils;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.logstash.plugins.PluginLookup.PluginType;
+import org.logstash.plugins.aliases.AliasDocumentReplace;
 import org.logstash.plugins.aliases.AliasPlugin;
 
 import java.io.FileInputStream;
@@ -24,6 +22,9 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Scanner;
+import java.util.stream.Collectors;
+
+import org.yaml.snakeyaml.Yaml;
 
 public class AliasRegistry {
 
@@ -100,13 +101,59 @@ private YamlWithChecksum(final String yamlContents, final String checksumHash) {
 
         @SuppressWarnings("unchecked")
         private Map<PluginType, List<AliasPlugin>> decodeYaml() throws IOException {
-            ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
-            return mapper.readValue(yamlContents, new TypeReference<Map<PluginType, List<AliasPlugin>>>() {});
+            Yaml yaml = new Yaml();
+            Map<String, Object> yamlMap = yaml.load(yamlContents);
+
+            // Convert the loaded YAML content to the expected type structure
+            return convertYamlMapToObject(yamlMap);
         }
 
         private String computeHashFromContent() {
             return DigestUtils.sha256Hex(yamlContents);
         }
+
+        @SuppressWarnings("unchecked")
+        private Map<PluginType, List<AliasPlugin>> convertYamlMapToObject(Map<String, Object> yamlMap) {
+            Map<PluginType, List<AliasPlugin>> result = new HashMap<>();
+
+            for (Map.Entry<String, Object> entry : yamlMap.entrySet()) {
+                PluginType pluginType = PluginType.valueOf(entry.getKey().toUpperCase());
+                List<Map<String, Object>> aliasList = (List<Map<String, Object>>) entry.getValue();
+
+                List<AliasPlugin> aliasPlugins = aliasList.stream()
+                        .map(YamlWithChecksum::convertToAliasPluginDefinition)
+                        .collect(Collectors.toList());
+
+                result.put(pluginType, aliasPlugins);
+            }
+            return result;
+        }
+
+        @SuppressWarnings("unchecked")
+        private static AliasPlugin convertToAliasPluginDefinition(Map<String, Object> aliasEntry) {
+            String aliasName = (String) aliasEntry.get("alias");
+            String from = (String) aliasEntry.get("from");
+
+            List<Map<String, String>> docs = (List<Map<String, String>>) aliasEntry.get("docs");
+            List<AliasDocumentReplace> replaceRules = convertToDocumentationReplacementRules(docs);
+
+            return new AliasPlugin(aliasName, from, replaceRules);
+        }
+
+        private static List<AliasDocumentReplace> convertToDocumentationReplacementRules(List<Map<String, String>> docs) {
+            if (docs == null) {
+                return Collections.emptyList();
+            }
+            return docs.stream()
+                    .map(YamlWithChecksum::convertSingleDocReplacementRule)
+                    .collect(Collectors.toList());
+        }
+
+        private static AliasDocumentReplace convertSingleDocReplacementRule(Map<String, String> doc) {
+            String replace = doc.get("replace");
+            String with = doc.get("with");
+            return new AliasDocumentReplace(replace, with);
+        }
     }
 
     static class AliasYamlLoader {

logstash-core/src/main/java/org/logstash/plugins/aliases/AliasDocumentReplace.java

@@ -19,6 +19,11 @@ public class AliasDocumentReplace {
     @Nonnull
     private String with;
 
+    public AliasDocumentReplace(String replace, String with) {
+        this.replace = replace;
+        this.with = with;
+    }
+
     public String getReplace() {
         return this.replace;
     }

logstash-core/src/main/java/org/logstash/plugins/aliases/AliasPlugin.java

@@ -15,22 +15,26 @@ public class AliasPlugin {
      * Name of the aliased plugin.
      */
     @Nonnull
-    @JsonProperty("alias")
-    private String aliasName;
+    private final String aliasName;
 
     /**
      * The plugin name where aliased plugin made from.
      */
     @Nonnull
-    private String from;
+    private final String from;
 
     /**
      * List of replace entries when transforming artifact doc to aliased plugin doc.
      */
     @Nullable
-    @JsonProperty("docs")
     private List<AliasDocumentReplace> docHeaderReplaces;
 
+    public AliasPlugin(String aliasName, String from, List<AliasDocumentReplace> docHeaderReplaces) {
+        this.aliasName = aliasName;
+        this.from = from;
+        this.docHeaderReplaces = docHeaderReplaces;
+    }
+
     @Nonnull
     public String getAliasName() {
         return aliasName;