Enhance UTF-8 handling and error refinement in modules

aether-datafixers-cli/src/main/java/de/splatgames/aether/datafixers/cli/command/MigrateCommand.java

@@ -42,6 +42,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
@@ -498,7 +499,7 @@ public Integer call() {
             if (this.generateReport && !reportBuilder.isEmpty()) {
                 final String reportContent = reportBuilder.toString();
                 if (this.reportFile != null) {
-                    Files.writeString(this.reportFile.toPath(), reportContent);
+                    Files.writeString(this.reportFile.toPath(), reportContent, StandardCharsets.UTF_8);
                 } else {
                     System.err.println(reportContent);
                 }
@@ -569,7 +570,7 @@ private <T> MigrationResult processFile(
         }
 
         // Read input (strip UTF-8 BOM if present)
-        String content = Files.readString(inputFile.toPath());
+        String content = Files.readString(inputFile.toPath(), StandardCharsets.UTF_8);
         if (content.startsWith("\uFEFF")) {
             content = content.substring(1);
         }
@@ -674,9 +675,9 @@ private void writeOutput(@NotNull final File inputFile, @NotNull final String co
 
             if (this.output.isDirectory()) {
                 final Path outPath = this.output.toPath().resolve(inputFile.getName());
-                Files.writeString(outPath, content);
+                Files.writeString(outPath, content, StandardCharsets.UTF_8);
             } else if (this.inputFiles.size() == 1) {
-                Files.writeString(this.output.toPath(), content);
+                Files.writeString(this.output.toPath(), content, StandardCharsets.UTF_8);
             } else {
                 throw new IllegalArgumentException(
                         "Output must be a directory when multiple input files are specified");
@@ -689,7 +690,7 @@ private void writeOutput(@NotNull final File inputFile, @NotNull final String co
             final Path tempPath = Files.createTempFile(
                     inputFile.toPath().getParent(), "migrate_", ".tmp");
             try {
-                Files.writeString(tempPath, content);
+                Files.writeString(tempPath, content, StandardCharsets.UTF_8);
                 if (this.backup) {
                     final String timestamp = ZonedDateTime.now(ZoneOffset.UTC)
                             .format(DateTimeFormatter.ofPattern("yyyyMMdd'T'HHmmss'Z'"));

aether-datafixers-cli/src/main/java/de/splatgames/aether/datafixers/cli/command/ValidateCommand.java

@@ -36,6 +36,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.List;
 import java.util.concurrent.Callable;
@@ -328,7 +329,7 @@ private <T> ValidationResult validateFile(
             if (fileSize > 100 * 1024 * 1024) {
                 throw new IOException("File exceeds maximum size (100MB): " + file);
             }
-            String content = Files.readString(file.toPath());
+            String content = Files.readString(file.toPath(), StandardCharsets.UTF_8);
             if (content.startsWith("\uFEFF")) {
                 content = content.substring(1);
             }

aether-datafixers-cli/src/main/java/de/splatgames/aether/datafixers/cli/format/YamlSnakeYamlFormatHandler.java

@@ -28,6 +28,7 @@
 import org.jetbrains.annotations.NotNull;
 import org.yaml.snakeyaml.DumperOptions;
 import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.error.YAMLException;
 
 /**
  * Format handler for YAML using the SnakeYAML library.
@@ -174,7 +175,7 @@ public Object parse(@NotNull final String content) {
                 throw new FormatParseException("YAML parsed to null");
             }
             return result;
-        } catch (final Exception e) {
+        } catch (final YAMLException | ClassCastException e) {
             throw new FormatParseException("Failed to parse YAML: " + e.getMessage(), e);
         }
     }

aether-datafixers-codec/src/main/java/de/splatgames/aether/datafixers/codec/json/gson/GsonOps.java

@@ -784,7 +784,7 @@ public DataResult<Stream<Pair<JsonElement, JsonElement>>> getMapEntries(
         return DataResult.success(
                 object.entrySet().stream()
                         .map(entry -> Pair.of(
-                                (JsonElement) new JsonPrimitive(entry.getKey()),
+                                new JsonPrimitive(entry.getKey()),
                                 entry.getValue()
                         ))
         );

aether-datafixers-core/src/main/java/de/splatgames/aether/datafixers/core/fix/DataFixerBuilder.java

@@ -155,11 +155,7 @@ public void registerAll(@NotNull final TypeReference type, @NotNull final Iterab
     public DataFixerBuilder addFix(@NotNull final TypeReference type, @NotNull final DataFix<?> fix) {
         Preconditions.checkNotNull(type, "type must not be null");
         Preconditions.checkNotNull(fix, "fix must not be null");
-        Preconditions.checkArgument(
-                fix.fromVersion().compareTo(fix.toVersion()) <= 0,
-                "fix.fromVersion must be <= fix.toVersion"
-        );
-
+        // Version ordering validation is performed by DataFixRegistry.register()
         this.registry.register(type, fix);
         return this;
     }

aether-datafixers-core/src/main/java/de/splatgames/aether/datafixers/core/fix/SimpleSystemDataFixerContext.java

@@ -63,11 +63,26 @@ private SimpleSystemDataFixerContext() {
 
     @Override
     public void info(@NotNull final String message, @Nullable final Object... args) {
-        System.out.printf("[INFO] " + message + "%n", args);
+        System.out.println("[INFO] " + formatMessage(message, args));
     }
 
     @Override
     public void warn(@NotNull final String message, @Nullable final Object... args) {
-        System.out.printf("[WARN] " + message + "%n", args);
+        System.err.println("[WARN] " + formatMessage(message, args));
+    }
+
+    private static String formatMessage(final String message, final Object[] args) {
+        if (args == null || args.length == 0) {
+            return message;
+        }
+        final StringBuilder result = new StringBuilder(message);
+        for (final Object arg : args) {
+            final int idx = result.indexOf("{}");
+            if (idx < 0) {
+                break;
+            }
+            result.replace(idx, idx + 2, String.valueOf(arg));
+        }
+        return result.toString();
     }
 }

aether-datafixers-core/src/main/java/de/splatgames/aether/datafixers/core/fix/Slf4jDataFixerContext.java

@@ -112,17 +112,15 @@ public Slf4jDataFixerContext(@NotNull final Logger logger) {
     @Override
     public void info(@NotNull final String message, @Nullable final Object... args) {
         Preconditions.checkNotNull(message, "message must not be null");
-        if (this.logger.isInfoEnabled()) {
-            this.logger.info(formatMessage(message, args));
-        }
+        // Delegate directly to SLF4J which handles {} placeholder formatting lazily
+        this.logger.info(message, args);
     }
 
     @Override
     public void warn(@NotNull final String message, @Nullable final Object... args) {
         Preconditions.checkNotNull(message, "message must not be null");
-        if (this.logger.isWarnEnabled()) {
-            this.logger.warn(formatMessage(message, args));
-        }
+        // Delegate directly to SLF4J which handles {} placeholder formatting lazily
+        this.logger.warn(message, args);
     }
 
     /**

aether-datafixers-spring-boot-starter/src/main/java/de/splatgames/aether/datafixers/spring/AetherDataFixersProperties.java

@@ -522,6 +522,7 @@ public String getDomainTag() {
          * @throws NullPointerException if domainTag is {@code null}
          */
         public void setDomainTag(@NotNull final String domainTag) {
+            Preconditions.checkArgument(!domainTag.isEmpty(), "domainTag must not be empty");
             this.domainTag = domainTag;
         }
     }

aether-datafixers-spring-boot-starter/src/main/java/de/splatgames/aether/datafixers/spring/autoconfigure/DataFixerAutoConfiguration.java

@@ -353,7 +353,7 @@ private static AetherDataFixer createFixer(
      */
     @SuppressFBWarnings(
             value = "NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE",
-            justification = "Null check for getCurrentVersion() is performed before access on line 363."
+            justification = "Null check for Field.get() result is performed before access via isAssignableFrom check."
     )
     @NotNull
     private static DataVersion resolveVersion(

aether-datafixers-testkit/src/main/java/de/splatgames/aether/datafixers/testkit/TestDataBuilder.java

@@ -29,6 +29,7 @@
 
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Objects;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
@@ -288,7 +289,7 @@ public TestDataBuilder<T> put(@NotNull final String key, final short value) {
     public TestDataBuilder<T> put(@NotNull final String key, @NotNull final Dynamic<T> value) {
         Preconditions.checkNotNull(key, "key must not be null");
         Preconditions.checkNotNull(value, "value must not be null");
-        Preconditions.checkArgument(this.ops == value.ops(),
+        Preconditions.checkArgument(Objects.equals(this.ops, value.ops()),
                 "Dynamic uses different DynamicOps");
         this.ensureObjectMode();
         this.fields.put(key, value);