Correctly name key mappers - rename "Snake"CaseKeyMapper

* The "snake case" key mapper was really kebab case.
* Add a real snake case key mapper, but clarify it as
  LowerSnakeCaseKeyMapper to prevent silently breaking API users.

Author: A248

backend-hocon/src/main/java/space/arim/dazzleconf/backend/hocon/HoconBackend.java

@@ -40,7 +40,7 @@
 import space.arim.dazzleconf.backend.DataTree;
 import space.arim.dazzleconf.backend.KeyMapper;
 import space.arim.dazzleconf.backend.ReadableRoot;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.engine.CommentLocation;
 import space.arim.dazzleconf.internals.lang.LibraryLang;
 
@@ -247,7 +247,7 @@ private ConfigValue entryToHocon(DataEntry entry) {
 
     @Override
     public @NonNull KeyMapper recommendKeyMapper() {
-        return new SnakeCaseKeyMapper();
+        return new KebabCaseKeyMapper();
     }
 
     @Override

backend-toml/src/main/java/space/arim/dazzleconf/backend/toml/TomlBackend.java

@@ -47,7 +47,7 @@
 import space.arim.dazzleconf.backend.KeyMapper;
 import space.arim.dazzleconf.backend.KeyPath;
 import space.arim.dazzleconf.backend.ReadableRoot;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.engine.CommentLocation;
 import space.arim.dazzleconf.internals.lang.LibraryLang;
 
@@ -324,7 +324,7 @@ private static CommentLocation commentLocationFrom(CommentPosition position) {
 
     @Override
     public @NonNull KeyMapper recommendKeyMapper() {
-        return new SnakeCaseKeyMapper();
+        return new KebabCaseKeyMapper();
     }
 
     @Override

backend-yaml/src/main/java/space/arim/dazzleconf/backend/yaml/ReadEvents.java

@@ -59,7 +59,7 @@
 import space.arim.dazzleconf.backend.DataEntry;
 import space.arim.dazzleconf.backend.DataList;
 import space.arim.dazzleconf.backend.DataTree;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.internals.lang.LibraryLang;
 
 import java.util.ArrayList;
@@ -147,7 +147,7 @@ private void consumeEventId(Event.ID eventId) {
             if (!parser.checkEvent(eventId)) {
                 // We can re-use SnakeCaseKeyMapper to build readable event names
                 // For example, StreamStart -> stream-start -> stream start
-                String displayName = new SnakeCaseKeyMapper().labelToKey(eventId.name()).toString();
+                String displayName = new KebabCaseKeyMapper().labelToKey(eventId.name()).toString();
                 String message = "Expected " + displayName.replace('-', ' ');
                 ErrorContext error = context.errorSource.buildError(preBuilt(message));
                 throw context.throwError(error, null);

backend-yaml/src/main/java/space/arim/dazzleconf/backend/yaml/YamlBackend.java

@@ -49,7 +49,7 @@
 import space.arim.dazzleconf.backend.CommentData;
 import space.arim.dazzleconf.backend.KeyMapper;
 import space.arim.dazzleconf.backend.ReadableRoot;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.engine.CommentLocation;
 import space.arim.dazzleconf.internals.lang.LibraryLang;
 
@@ -328,7 +328,7 @@ private static void writeComments(Writer writer, List<String> lines) throws IOEx
 
     @Override
     public @NonNull KeyMapper recommendKeyMapper() {
-        return new SnakeCaseKeyMapper();
+        return new KebabCaseKeyMapper();
     }
 
     @Override

…zzleconf/backend/SnakeCaseKeyMapper.java …rim/dazzleconf/backend/CamelCaseMap.javacore/src/main/java/space/arim/dazzleconf/backend/SnakeCaseKeyMapper.java renamed to core/src/main/java/space/arim/dazzleconf/backend/CamelCaseMap.java core/src/main/java/space/arim/dazzleconf/backend/SnakeCaseKeyMapper.java renamed to core/src/main/java/space/arim/dazzleconf/backend/CamelCaseMap.java

@@ -19,26 +19,11 @@
 
 package space.arim.dazzleconf.backend;
 
-import org.checkerframework.checker.nullness.qual.NonNull;
+final class CamelCaseMap {
 
-/**
- * A key mapper which converts lower camel case patterns to lower snake case.
- * <p>
- * This is intended for use with YAML and TOML and other formats that use lower snake case. For example, a method
- * named "myConfOption" will become "my-conf-option" using this key mapper.
- *
- */
-public final class SnakeCaseKeyMapper implements KeyMapper {
-
-    /**
-     * Creates
-     *
-     */
-    public SnakeCaseKeyMapper() {}
-
-    @Override
-    public @NonNull CharSequence labelToKey(@NonNull CharSequence label) {
+    private CamelCaseMap() {}
 
+    static CharSequence toCasedLower(CharSequence label, char separator) {
         StringBuilder builder = new StringBuilder();
         int startAppend = 0;
 
@@ -48,7 +33,7 @@ public SnakeCaseKeyMapper() {}
                 // Found a segment: append everything before us
                 builder.append(label, startAppend, n);
                 if (n != 0) {
-                    builder.append('-');
+                    builder.append(separator);
                 }
                 builder.append(Character.toLowerCase(currentChar));
                 startAppend = n + 1;

core/src/main/java/space/arim/dazzleconf/backend/KebabCaseKeyMapper.java

@@ -0,0 +1,42 @@
+/*
+ * DazzleConf
+ * Copyright © 2025 Anand Beh
+ *
+ * DazzleConf is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * DazzleConf is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with DazzleConf. If not, see <https://www.gnu.org/licenses/>
+ * and navigate to version 3 of the GNU Lesser General Public License.
+ */
+
+package space.arim.dazzleconf.backend;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+/**
+ * A key mapper which converts lower camel case patterns to kebab case.
+ * <p>
+ * This is intended for use with YAML and TOML and other formats that use kebab case. For example, a method
+ * named "myConfOption" will become "my-conf-option" using this key mapper.
+ *
+ */
+public final class KebabCaseKeyMapper implements KeyMapper {
+
+    /**
+     * Creates
+     */
+    public KebabCaseKeyMapper() {}
+
+    @Override
+    public @NonNull CharSequence labelToKey(@NonNull CharSequence label) {
+        return CamelCaseMap.toCasedLower(label, '-');
+    }
+}

core/src/main/java/space/arim/dazzleconf/backend/LowerSnakeCaseKeyMapper.java

@@ -0,0 +1,42 @@
+/*
+ * DazzleConf
+ * Copyright © 2025 Anand Beh
+ *
+ * DazzleConf is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * DazzleConf is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with DazzleConf. If not, see <https://www.gnu.org/licenses/>
+ * and navigate to version 3 of the GNU Lesser General Public License.
+ */
+
+package space.arim.dazzleconf.backend;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+/**
+ * A key mapper which converts lower camel case patterns to snake case.
+ * <p>
+ * For example, a method named "myConfOption" will become "my_conf_option" using this key mapper. This is the naming
+ * scheme (by convention) for SQL columns, Python fields and functions, and Rust struct fields.
+ *
+ */
+public final class LowerSnakeCaseKeyMapper implements KeyMapper {
+
+    /**
+     * Creates
+     */
+    public LowerSnakeCaseKeyMapper() {}
+
+    @Override
+    public @NonNull CharSequence labelToKey(@NonNull CharSequence label) {
+        return CamelCaseMap.toCasedLower(label, '_');
+    }
+}

core/src/test/java/space/arim/dazzleconf/ConfigurationMechanicsTest.java

@@ -33,7 +33,7 @@
 import space.arim.dazzleconf.backend.DataTree;
 import space.arim.dazzleconf.backend.KeyMapper;
 import space.arim.dazzleconf.backend.KeyPath;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.engine.CommentLocation;
 import space.arim.dazzleconf.engine.Comments;
 import space.arim.dazzleconf.engine.UpdateListener;
@@ -61,7 +61,7 @@ public class ConfigurationMechanicsTest {
 
     private Configuration<Config> configuration;
     private final UpdateListener updateListener;
-    private final KeyMapper keyMapper = new SnakeCaseKeyMapper();
+    private final KeyMapper keyMapper = new KebabCaseKeyMapper();
 
     public ConfigurationMechanicsTest(@Mock UpdateListener updateListener) {
         this.updateListener = updateListener;

core/src/test/java/space/arim/dazzleconf/ErrorPrintingTest.java

@@ -27,7 +27,7 @@
 import space.arim.dazzleconf.backend.KeyMapper;
 import space.arim.dazzleconf.backend.KeyPath;
 import space.arim.dazzleconf.backend.Printable;
-import space.arim.dazzleconf.backend.SnakeCaseKeyMapper;
+import space.arim.dazzleconf.backend.KebabCaseKeyMapper;
 import space.arim.dazzleconf.engine.UpdateReason;
 import space.arim.dazzleconf.engine.liaison.SubSection;
 import space.arim.dazzleconf.reflect.DefaultReflectionService;
@@ -89,7 +89,7 @@ public void notifyUpdate(@NonNull KeyPath entryPath, @NonNull UpdateReason updat
 
                     @Override
                     public @NonNull KeyMapper keyMapper() {
-                        return new SnakeCaseKeyMapper();
+                        return new KebabCaseKeyMapper();
                     }
 
                     @Override

…conf/backend/SnakeCaseKeyMapperTest.java …conf/backend/KebabCaseKeyMapperTest.javacore/src/test/java/space/arim/dazzleconf/backend/SnakeCaseKeyMapperTest.java renamed to core/src/test/java/space/arim/dazzleconf/backend/KebabCaseKeyMapperTest.java core/src/test/java/space/arim/dazzleconf/backend/SnakeCaseKeyMapperTest.java renamed to core/src/test/java/space/arim/dazzleconf/backend/KebabCaseKeyMapperTest.java

@@ -23,9 +23,9 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-public class SnakeCaseKeyMapperTest {
+public class KebabCaseKeyMapperTest {
 
-    private final KeyMapper keyMapper = new SnakeCaseKeyMapper();
+    private final KeyMapper keyMapper = new KebabCaseKeyMapper();
 
     @Test
     public void simple() {