Suppress "this-escape" warnings in Java 21. (#765)

Should actually be solved by either refactoring or `final`izing methods/classes.

See also: https://bugs.openjdk.org/browse/JDK-8299995

--------

* JDK 21:

- "warning: [this-escape] possible 'this' escape before subclass is fully initialized"
- "warning: [this-escape] previous possible 'this' escape happens here via invocation"

Author: blackwinter

metafacture-html/src/main/java/org/metafacture/html/HtmlDecoder.java

@@ -129,7 +129,7 @@ private boolean handleAttributeValuesAsSubfields(final StreamReceiver receiver,
      *
      * @param mapString the attributes to be added as subfields
      */
-    public void setAttrValsAsSubfields(final String mapString) {
+    public final void setAttrValsAsSubfields(final String mapString) {
         this.attrValsAsSubfields = new HashMap<>();
         final String input = mapString.startsWith("&") ? DEFAULT_ATTR_VALS_AS_SUBFIELDS + mapString : mapString;
         for (final String nameValuePair : input.split("&")) {

metafacture-triples/src/main/java/org/metafacture/triples/AbstractTripleSort.java

@@ -82,6 +82,7 @@ public int order(final int indicator) {
     /**
      * Constructs an AbstractTripleSort. Calls {@link MemoryWarningSystem}.
      */
+    @SuppressWarnings("this-escape")
     protected AbstractTripleSort() {
         MemoryWarningSystem.addListener(this);
     }

metafix/build.gradle

@@ -92,6 +92,14 @@ test {
   maxParallelForks = Runtime.runtime.availableProcessors().intdiv(2) ?: 1
 }
 
+tasks.withType(JavaCompile) {
+  // JDK 21:
+  // metafix/src/main/xtext-gen/org/metafacture/metafix/parser/antlr/internal/InternalFixParser.java:139:
+  // warning: [this-escape] possible 'this' escape before subclass is fully initialized
+  // => TODO: Drop after removal of Xtext (see issue #579)
+  options.compilerArgs << '-Xlint:-this-escape'
+}
+
 task integrationTest(type: Exec, group: 'Verification') {
   def installDist = ':metafacture-runner:installDist'
   dependsOn installDist

metafix/src/main/java/org/metafacture/metafix/ListFixPaths.java

@@ -40,6 +40,7 @@ public class ListFixPaths extends MetafixStreamAnalyzer {
     /**
      * Creates an instance of {@link ListFixPaths}.
      */
+    @SuppressWarnings("this-escape")
     public ListFixPaths() {
         super("nothing()", Compare.PREDICATE);
         setIndex(false);

metafix/src/main/java/org/metafacture/metafix/Metafix.java

@@ -132,6 +132,7 @@ public Metafix(final Map<String, String> vars) {
      * @param function an optional function that accepts the Metafix instance
      *                 and returns the Fix variables as a Map, or {@code null}
      */
+    @SuppressWarnings("this-escape")
     public Metafix(final Function<Metafix, Map<String, String>> function) {
         init(function);
         recordTransformer = null;
@@ -169,6 +170,7 @@ public Metafix(final String fixDef, final Map<String, String> vars) throws IOExc
      *
      * @throws IOException if an I/O error occurs
      */
+    @SuppressWarnings("this-escape")
     public Metafix(final String fixDef, final Function<Metafix, Map<String, String>> function) throws IOException {
         init(function);
 
@@ -209,6 +211,7 @@ public Metafix(final Reader fixDef, final Map<String, String> vars) {
      * @param function an optional function that accepts the Metafix instance
      *                 and returns the Fix variables as a Map, or {@code null}
      */
+    @SuppressWarnings("this-escape")
     public Metafix(final Reader fixDef, final Function<Metafix, Map<String, String>> function) {
         init(function);
         recordTransformer = getRecordTransformer(fixDef);

metafix/src/main/java/org/metafacture/metafix/api/FixRegistry.java

@@ -65,6 +65,7 @@ public class FixRegistry {
      * Creates an instance of {@link FixRegistry}. {@link #registerProperties(String) Registers}
      * all Fix commands found in any {@value PROPERTIES_LOCATION} files.
      */
+    @SuppressWarnings("this-escape")
     public FixRegistry() {
         registerProperties(PROPERTIES_LOCATION);
     }