Allow rules to declare they only accept a set of options (#1560)

src/main/java/carpet/api/settings/CarpetRule.java

@@ -85,6 +85,18 @@ public interface CarpetRule<T> {
      */
     T defaultValue();
     
+    /**
+     * <p>Returns whether this rule is strict.</p>
+     * 
+     * <p>A rule being strict means that it will only accept the suggestions returned by {@link #suggestions()} as valid values.</p>
+     * 
+     * <p>Note that a rule implementation may return {@code false} in this method but still not accept options other than those
+     * returned in {@link #suggestions()}, only the opposite is guaranteed.</p>
+     */
+    default boolean strict() {
+        return false;
+    }
+    
     /**
      * <p>Sets this rule's value to the provided {@link String}, after first converting the {@link String} into a suitable type.</p>
      * 

src/main/java/carpet/api/settings/SettingsManager.java

@@ -533,7 +533,7 @@ public class SettingsManager {
             ps.println("* Type: `" + rule.type().getSimpleName() + "`  ");
             ps.println("* Default value: `" + RuleHelper.toRuleString(rule.defaultValue()) + "`  ");
             String options = rule.suggestions().stream().map(s -> "`" + s + "`").collect(Collectors.joining(", "));
-            if (!options.isEmpty()) ps.println((rule instanceof ParsedRule<?> pr && pr.isStrict?"* Required":"* Suggested")+" options: " + options + "  ");
+            if (!options.isEmpty()) ps.println((rule.strict() ? "* Required" : "* Suggested") + " options: " + options + "  ");
             ps.println("* Categories: " + rule.categories().stream().map(s -> "`" + s.toUpperCase(Locale.ROOT) + "`").collect(Collectors.joining(", ")) + "  ");
             if (rule instanceof ParsedRule<?>)
             {