[serde-gson] Support for Gson readers and writers

buildSrc/src/main/kotlin/de.siphalor.tweed5.base-module.gradle.kts

@@ -51,7 +51,7 @@ dependencies {
     testImplementation(libs.mockito)
     testAgent(libs.mockito)
     testImplementation(libs.assertj)
-    testImplementation(project(":test-utils"))
+    testImplementation(project(":generic-test-utils"))
 }
 
 tasks.compileTestJava {

buildSrc/src/main/kotlin/de.siphalor.tweed5.test-utils.gradle.kts

@@ -0,0 +1,28 @@
+import gradle.kotlin.dsl.accessors._182d53d78a136df48d95cf7411f9259f.lombok
+import org.gradle.kotlin.dsl.assign
+
+plugins {
+	java
+	alias(libs.plugins.lombok)
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation(project(":tweed5-serde-api"))
+	implementation(platform(libs.junit.platform))
+	implementation(libs.junit.core)
+	implementation(libs.mockito)
+	implementation(libs.assertj)
+}
+
+lombok {
+	version = libs.versions.lombok.get()
+}
+
+java {
+	sourceCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
+	targetCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
+}

gradle/libs.versions.toml

@@ -3,6 +3,7 @@ assertj = "3.26.3"
 asm = "9.7"
 autoservice = "1.1.1"
 acl = "1.3.5"
+gson = "2.13.1"
 jackson = "2.19.0"
 java-main = "8"
 java-test = "21"
@@ -26,6 +27,7 @@ asm-commons = { group = "org.ow2.asm", name = "asm-commons", version.ref = "asm"
 asm-core = { group = "org.ow2.asm", name = "asm", version.ref = "asm" }
 autoservice-annotations = { group = "com.google.auto.service", name = "auto-service-annotations", version.ref = "autoservice" }
 autoservice-processor = { group = "com.google.auto.service", name = "auto-service", version.ref = "autoservice" }
+gson = { group = "com.google.code.gson", name = "gson", version.ref = "gson" }
 jackson-core = { group = "com.fasterxml.jackson.core", name = "jackson-core", version.ref = "jackson" }
 jetbrains-annotations = { group = "org.jetbrains", name = "annotations", version.ref = "jetbrains-annotations" }
 jspecify-annotations = { group = "org.jspecify", name = "jspecify", version.ref = "jspecify" }

settings.gradle.kts

@@ -10,6 +10,7 @@ include("tweed5-naming-format")
 include("tweed5-patchwork")
 include("tweed5-serde-api")
 include("tweed5-serde-extension")
+include("tweed5-serde-gson")
 include("tweed5-serde-hjson")
 include("tweed5-serde-jackson")
 include("tweed5-type-utils")
@@ -21,6 +22,9 @@ include("tweed5-weaver-pojo-validation-extension")
 
 includeAs("minecraft:tweed5-bundle", "minecraft/tweed5-bundle")
 
+includeAs("generic-test-utils", "test-utils/generic")
+includeAs("serde-json-test-utils", "test-utils/serde-json")
+
 fun includeAs(name: String, path: String) {
     include(name)
     project(":$name").projectDir = file(path)

test-utils/build.gradle.kts

@@ -1,8 +0,0 @@
-plugins {
-	java
-}
-
-java {
-	sourceCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
-	targetCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
-}

test-utils/generic/build.gradle.kts

@@ -0,0 +1,3 @@
+plugins {
+	id("de.siphalor.tweed5.test-utils")
+}

test-utils/generic/src/main/java/de/siphalor/tweed5/testutils/generic/MapTestUtils.java

@@ -1,4 +1,4 @@
-package de.siphalor.tweed5.testutils;
+package de.siphalor.tweed5.testutils.generic;
 
 import java.util.*;
 

test-utils/serde-json/build.gradle.kts

@@ -0,0 +1,3 @@
+plugins {
+	id("de.siphalor.tweed5.test-utils")
+}

test-utils/serde-json/src/main/java/de/siphalor/tweed5/testutils/serde/json/JsonReaderTest.java

@@ -0,0 +1,73 @@
+package de.siphalor.tweed5.testutils.serde.json;
+
+import de.siphalor.tweed5.dataapi.api.TweedDataReader;
+import lombok.SneakyThrows;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public interface JsonReaderTest {
+	TweedDataReader createJsonReader(String text);
+
+	@Test
+	@SneakyThrows
+	default void complexJsonReadTest() {
+		var reader = createJsonReader("""
+				{
+					"first": [
+						[ 1 ]
+					],
+					"second": {
+						"test": "Hello World!"
+					}
+				}
+				""");
+
+		var token = reader.peekToken();
+		assertThat(token.isMapStart()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapStart()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapEntryKey()).isTrue();
+		assertThat(token.canReadAsString()).isTrue();
+		assertThat(token.readAsString()).isEqualTo("first");
+		token = reader.readToken();
+		assertThat(token.isMapEntryValue()).isTrue();
+		assertThat(token.isListStart()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapEntryValue()).isFalse();
+		assertThat(token.isListValue()).isTrue();
+		assertThat(token.isListStart()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isListValue()).isTrue();
+		assertThat(token.canReadAsInt()).isTrue();
+		assertThat(token.readAsInt()).isEqualTo(1);
+		token = reader.readToken();
+		assertThat(token.isListValue()).isTrue();
+		assertThat(token.isListEnd()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isListValue()).isFalse();
+		assertThat(token.isMapEntryValue()).isTrue();
+		assertThat(token.isListEnd()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapEntryKey()).isTrue();
+		assertThat(token.canReadAsString()).isTrue();
+		assertThat(token.readAsString()).isEqualTo("second");
+		token = reader.readToken();
+		assertThat(token.isMapEntryValue()).isTrue();
+		assertThat(token.isMapStart()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapEntryValue()).isFalse();
+		assertThat(token.isMapEntryKey()).isTrue();
+		assertThat(token.canReadAsString()).isTrue();
+		assertThat(token.readAsString()).isEqualTo("test");
+		token = reader.readToken();
+		assertThat(token.isMapEntryValue()).isTrue();
+		assertThat(token.canReadAsString()).isTrue();
+		assertThat(token.readAsString()).isEqualTo("Hello World!");
+		token = reader.readToken();
+		assertThat(token.isMapEnd()).isTrue();
+		token = reader.readToken();
+		assertThat(token.isMapEnd()).isTrue();
+	}
+}

tweed5-attributes-extension/src/test/java/de/siphalor/tweed5/attributesextension/impl/serde/filter/AttributesReadWriteFilterExtensionImplTest.java

@@ -23,14 +23,13 @@ import java.io.StringWriter;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Consumer;
 
 import static de.siphalor.tweed5.attributesextension.api.AttributesExtension.attribute;
 import static de.siphalor.tweed5.attributesextension.api.AttributesExtension.attributeDefault;
 import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.*;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.compoundReaderWriter;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.stringReaderWriter;
-import static de.siphalor.tweed5.testutils.MapTestUtils.sequencedMap;
+import static de.siphalor.tweed5.testutils.generic.MapTestUtils.sequencedMap;
 import static java.util.Map.entry;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.InstanceOfAssertFactories.map;

tweed5-default-extensions/src/test/java/de/siphalor/tweed5/defaultextensions/comment/impl/CommentExtensionImplTest.java

@@ -27,7 +27,7 @@ import java.util.Map;
 import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.entryReaderWriter;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.*;
 import static de.siphalor.tweed5.defaultextensions.comment.api.CommentExtension.baseComment;
-import static de.siphalor.tweed5.testutils.MapTestUtils.sequencedMap;
+import static de.siphalor.tweed5.testutils.generic.MapTestUtils.sequencedMap;
 import static java.util.Map.entry;
 import static org.junit.jupiter.api.Assertions.*;
 

tweed5-default-extensions/src/test/java/de/siphalor/tweed5/defaultextensions/patch/impl/PatchExtensionImplTest.java

@@ -28,7 +28,7 @@ import java.util.stream.Stream;
 import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.entryReaderWriter;
 import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.read;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.*;
-import static de.siphalor.tweed5.testutils.MapTestUtils.sequencedMap;
+import static de.siphalor.tweed5.testutils.generic.MapTestUtils.sequencedMap;
 import static java.util.Map.entry;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.params.provider.Arguments.argumentSet;

tweed5-default-extensions/src/test/java/de/siphalor/tweed5/defaultextensions/validation/impl/ValidationExtensionImplTest.java

@@ -33,7 +33,7 @@ import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.read;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.*;
 import static de.siphalor.tweed5.defaultextensions.comment.api.CommentExtension.baseComment;
 import static de.siphalor.tweed5.defaultextensions.validation.api.ValidationExtension.validators;
-import static de.siphalor.tweed5.testutils.MapTestUtils.sequencedMap;
+import static de.siphalor.tweed5.testutils.generic.MapTestUtils.sequencedMap;
 import static java.util.Map.entry;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.*;

tweed5-serde-extension/src/test/java/de/siphalor/tweed5/data/extension/impl/ReadWriteExtensionImplTest.java

@@ -24,7 +24,7 @@ import java.util.function.Function;
 
 import static de.siphalor.tweed5.data.extension.api.ReadWriteExtension.entryReaderWriter;
 import static de.siphalor.tweed5.data.extension.api.readwrite.TweedEntryReaderWriters.*;
-import static de.siphalor.tweed5.testutils.MapTestUtils.sequencedMap;
+import static de.siphalor.tweed5.testutils.generic.MapTestUtils.sequencedMap;
 import static java.util.Map.entry;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;

tweed5-serde-gson/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+    id("de.siphalor.tweed5.base-module")
+	id("de.siphalor.tweed5.minecraft.mod.dummy")
+	id("de.siphalor.tweed5.shadow.explicit")
+}
+
+dependencies {
+    implementation(project(":tweed5-serde-api"))
+	implementation(libs.gson)
+
+	testImplementation(project(":serde-json-test-utils"))
+}
+

tweed5-serde-gson/gradle.properties

@@ -0,0 +1,2 @@
+minecraft.mod.name = Tweed 5 Gson
+minecraft.mod.description = Tweed 5 module that adds support for reading and writing JSON using the Gson library.

tweed5-serde-gson/src/main/java/de/siphaolor/tweed5/data/gson/GsonReader.java

@@ -0,0 +1,275 @@
+package de.siphaolor.tweed5.data.gson;
+
+import com.google.gson.stream.JsonReader;
+import de.siphalor.tweed5.dataapi.api.TweedDataReadException;
+import de.siphalor.tweed5.dataapi.api.TweedDataReader;
+import de.siphalor.tweed5.dataapi.api.TweedDataToken;
+import de.siphalor.tweed5.dataapi.api.TweedDataTokens;
+import org.jspecify.annotations.Nullable;
+
+import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+public class GsonReader implements TweedDataReader {
+	private final JsonReader reader;
+
+	private final Deque<Context> contextStack = new ArrayDeque<>();
+
+	private @Nullable TweedDataToken peekedToken;
+
+	public GsonReader(JsonReader reader) {
+		this.reader = reader;
+		contextStack.push(Context.VALUE);
+	}
+
+	@Override
+	public TweedDataToken peekToken() throws TweedDataReadException {
+		if (peekedToken == null) {
+			peekedToken = nextToken();
+		}
+		return peekedToken;
+	}
+
+	@Override
+	public TweedDataToken readToken() throws TweedDataReadException {
+		if (peekedToken != null) {
+			TweedDataToken token = peekedToken;
+			peekedToken = null;
+			return token;
+		}
+		return nextToken();
+	}
+
+	private TweedDataToken nextToken() throws TweedDataReadException {
+		try {
+			switch (reader.peek()) {
+				case BEGIN_ARRAY: {
+					reader.beginArray();
+					TweedDataToken token = wrapToken(TweedDataTokens.getListStart());
+					contextStack.push(Context.LIST);
+					return token;
+				}
+				case END_ARRAY: {
+					reader.endArray();
+					popContext(Context.LIST);
+					TweedDataToken token = wrapToken(TweedDataTokens.getListEnd());
+					afterValueRead();
+					return token;
+				}
+				case BEGIN_OBJECT: {
+					reader.beginObject();
+					TweedDataToken token = wrapToken(TweedDataTokens.getMapStart());
+					contextStack.push(Context.MAP);
+					return token;
+				}
+				case END_OBJECT: {
+					reader.endObject();
+					popContext(Context.MAP);
+					TweedDataToken token = wrapToken(TweedDataTokens.getMapEnd());
+					afterValueRead();
+					return token;
+				}
+				case NAME:
+					contextStack.push(Context.MAP_ENTRY_VALUE);
+					return TweedDataTokens.asMapEntryKey(createStringToken(reader.nextName()));
+				case NULL: {
+					reader.nextNull();
+					TweedDataToken token = wrapToken(TweedDataTokens.getNull());
+					afterValueRead();
+					return token;
+				}
+				case BOOLEAN: {
+					boolean value = reader.nextBoolean();
+					TweedDataToken token = wrapToken(new TweedDataToken() {
+						@Override
+						public boolean canReadAsBoolean() {
+							return true;
+						}
+
+						@Override
+						public boolean readAsBoolean() throws TweedDataReadException {
+							return value;
+						}
+					});
+					afterValueRead();
+					return token;
+				}
+				case NUMBER: {
+					Long longValue = tryReadLong();
+					TweedDataToken token;
+					if (longValue != null) {
+						token = wrapToken(new TweedDataToken() {
+							@Override
+							public boolean canReadAsByte() {
+								return longValue >= Byte.MIN_VALUE && longValue <= Byte.MAX_VALUE;
+							}
+
+							@Override
+							public byte readAsByte() {
+								return longValue.byteValue();
+							}
+
+							@Override
+							public boolean canReadAsShort() {
+								return longValue >= Short.MIN_VALUE && longValue <= Short.MAX_VALUE;
+							}
+
+							@Override
+							public short readAsShort() {
+								return longValue.shortValue();
+							}
+
+							@Override
+							public boolean canReadAsInt() {
+								return longValue >= Integer.MIN_VALUE && longValue <= Integer.MAX_VALUE;
+							}
+
+							@Override
+							public int readAsInt() {
+								return longValue.intValue();
+							}
+
+							@Override
+							public boolean canReadAsLong() {
+								return true;
+							}
+
+							@Override
+							public long readAsLong() {
+								return longValue;
+							}
+
+							@Override
+							public boolean canReadAsFloat() {
+								return true;
+							}
+
+							@Override
+							public float readAsFloat() {
+								return longValue.floatValue();
+							}
+
+							@Override
+							public boolean canReadAsDouble() {
+								return true;
+							}
+
+							@Override
+							public double readAsDouble() {
+								return longValue.doubleValue();
+							}
+						});
+					} else {
+						double doubleValue = reader.nextDouble();
+						token = wrapToken(new TweedDataToken() {
+							@Override
+							public boolean canReadAsFloat() {
+								return true;
+							}
+
+							@Override
+							public float readAsFloat() {
+								return (float) doubleValue;
+							}
+
+							@Override
+							public boolean canReadAsDouble() {
+								return true;
+							}
+
+							@Override
+							public double readAsDouble() {
+								return doubleValue;
+							}
+						});
+					}
+					afterValueRead();
+					return token;
+				}
+				case STRING: {
+					TweedDataToken token = wrapToken(createStringToken(reader.nextString()));
+					afterValueRead();
+					return token;
+				}
+				default:
+					throw TweedDataReadException.builder()
+							.message("Encountered unexpected " + peekedToken + " token at " + reader.getPath())
+							.build();
+			}
+		} catch (IOException e) {
+			throw TweedDataReadException.builder()
+					.message("Error reading data using gson at " + reader.getPath())
+					.cause(e)
+					.build();
+		}
+	}
+
+	private @Nullable Long tryReadLong() throws IOException {
+		try {
+			return reader.nextLong();
+		} catch (NumberFormatException e) {
+			return null;
+		}
+	}
+
+	private TweedDataToken wrapToken(TweedDataToken token) throws TweedDataReadException {
+		switch (peekContext()) {
+			case MAP_ENTRY_VALUE:
+				return TweedDataTokens.asMapEntryValue(token);
+			case LIST:
+				return TweedDataTokens.asListValue(token);
+			default:
+				return token;
+		}
+	}
+
+	private void afterValueRead() throws TweedDataReadException {
+		Context context = peekContext();
+		switch (context) {
+			case MAP_ENTRY_VALUE:
+			case VALUE:
+				popContext(context);
+		}
+	}
+
+	private Context peekContext() throws TweedDataReadException {
+		Context context = contextStack.peek();
+		if (context == null) {
+			throw TweedDataReadException.builder()
+					.message("Tried to read context but currently not in any context")
+					.build();
+		}
+		return context;
+	}
+
+	private void popContext(Context expectedContext) throws TweedDataReadException {
+		Context context = contextStack.pop();
+		if (context != expectedContext) {
+			throw TweedDataReadException.builder()
+					.message("Unexpected context " + context + " when popping " + expectedContext)
+					.build();
+		}
+	}
+
+	private TweedDataToken createStringToken(String value) {
+		return new TweedDataToken() {
+			@Override
+			public boolean canReadAsString() {
+				return true;
+			}
+
+			@Override
+			public String readAsString() {
+				return value;
+			}
+		};
+	}
+
+	private enum Context {
+		VALUE,
+		LIST,
+		MAP,
+		MAP_ENTRY_VALUE,
+	}
+}

tweed5-serde-gson/src/main/java/de/siphaolor/tweed5/data/gson/GsonWriter.java

@@ -0,0 +1,214 @@
+package de.siphaolor.tweed5.data.gson;
+
+import com.google.gson.stream.JsonWriter;
+import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
+import de.siphalor.tweed5.dataapi.api.TweedDataWriteException;
+import de.siphalor.tweed5.dataapi.api.decoration.TweedDataCommentDecoration;
+import de.siphalor.tweed5.dataapi.api.decoration.TweedDataDecoration;
+import org.jspecify.annotations.Nullable;
+
+import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+public class GsonWriter implements TweedDataVisitor {
+	private final JsonWriter writer;
+
+	private final Deque<Context> contextStack = new ArrayDeque<>();
+
+	private @Nullable String deferredFieldComment;
+
+	public GsonWriter(JsonWriter writer) {
+		this.writer = writer;
+		this.contextStack.push(Context.VALUE);
+	}
+
+	@Override
+	public void visitNull() {
+		try {
+			writer.nullValue();
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitBoolean(boolean value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitByte(byte value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitShort(short value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitInt(int value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitLong(long value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitFloat(float value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitDouble(double value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitString(String value) {
+		try {
+			writer.value(value);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitListStart() {
+		try {
+			writer.beginArray();
+			contextStack.push(Context.LIST);
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitListEnd() {
+		try {
+			writer.endArray();
+			popContext(Context.LIST);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitMapStart() {
+		try {
+			writer.beginObject();
+			contextStack.push(Context.MAP);
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitMapEntryKey(String key) {
+		try {
+			if (deferredFieldComment != null) {
+				writer.name(key + "__comment");
+				writer.value(deferredFieldComment);
+				deferredFieldComment = null;
+			}
+			writer.name(key);
+			contextStack.push(Context.VALUE);
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitMapEnd() {
+		try {
+			writer.endObject();
+			popContext(Context.MAP);
+			afterValueWritten();
+		} catch (IOException e) {
+			throw createWriteExceptionFromIoException(e);
+		}
+	}
+
+	@Override
+	public void visitDecoration(TweedDataDecoration decoration) {
+		if (decoration instanceof TweedDataCommentDecoration) {
+			if (deferredFieldComment == null) {
+				deferredFieldComment = ((TweedDataCommentDecoration) decoration).comment();
+			} else {
+				deferredFieldComment += "\n" + ((TweedDataCommentDecoration) decoration).comment();
+			}
+		}
+	}
+
+	private void afterValueWritten() {
+		if (peekContext() == Context.VALUE) {
+			contextStack.pop();
+		}
+	}
+
+	private void popContext(Context expectedContext) {
+		Context context = contextStack.pop();
+		if (context != expectedContext) {
+			throw new TweedDataWriteException("Unexpected context " + context + " when popping " + expectedContext);
+		}
+	}
+
+	private Context peekContext() {
+		Context context = contextStack.peek();
+		if (context == null) {
+			throw new TweedDataWriteException("Tried to read context but currently not in any context");
+		}
+		return context;
+	}
+
+	private TweedDataWriteException createWriteExceptionFromIoException(IOException e) {
+		return new TweedDataWriteException("Error writing data using Gson", e);
+	}
+
+	private enum Context {
+		VALUE,
+		LIST,
+		MAP,
+	}
+}

tweed5-serde-gson/src/main/java/de/siphaolor/tweed5/data/gson/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphaolor.tweed5.data.gson;
+
+import org.jspecify.annotations.NullMarked;

tweed5-serde-gson/src/test/java/de/siphaolor/tweed5/data/gson/GsonReaderTest.java

@@ -0,0 +1,16 @@
+package de.siphaolor.tweed5.data.gson;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.stream.JsonReader;
+import de.siphalor.tweed5.dataapi.api.TweedDataReader;
+import de.siphalor.tweed5.testutils.serde.json.JsonReaderTest;
+
+import java.io.StringReader;
+
+class GsonReaderTest implements JsonReaderTest {
+	@Override
+	public TweedDataReader createJsonReader(String text) {
+		JsonReader jsonReader = new GsonBuilder().create().newJsonReader(new StringReader(text));
+		return new GsonReader(jsonReader);
+	}
+}

tweed5-serde-gson/src/test/java/de/siphaolor/tweed5/data/gson/GsonWriterTest.java

@@ -0,0 +1,54 @@
+package de.siphaolor.tweed5.data.gson;
+
+import com.google.gson.GsonBuilder;
+import de.siphalor.tweed5.dataapi.api.decoration.TweedDataCommentDecoration;
+import lombok.SneakyThrows;
+import org.junit.jupiter.api.Test;
+
+import java.io.StringWriter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class GsonWriterTest {
+
+	@SneakyThrows
+	@Test
+	void complex() {
+		var stringWriter = new StringWriter();
+		var writer = new GsonWriter(new GsonBuilder().setPrettyPrinting().create().newJsonWriter(stringWriter));
+
+		writer.visitMapStart();
+
+		writer.visitMapEntryKey("first");
+		writer.visitListStart();
+		writer.visitInt(123);
+		writer.visitListStart();
+		writer.visitBoolean(false);
+		writer.visitListEnd();
+		writer.visitListEnd();
+
+		writer.visitDecoration((TweedDataCommentDecoration) () -> "Hello");
+		writer.visitDecoration((TweedDataCommentDecoration) () -> "World");
+		writer.visitMapEntryKey("second");
+		writer.visitMapStart();
+		writer.visitMapEntryKey("nested");
+		writer.visitDouble(12.34);
+		writer.visitMapEnd();
+
+		writer.visitMapEnd();
+
+		assertThat(stringWriter.toString()).isEqualTo("""
+				{
+				  "first": [
+				    123,
+				    [
+				      false
+				    ]
+				  ],
+				  "second__comment": "Hello\\nWorld",
+				  "second": {
+				    "nested": 12.34
+				  }
+				}""");
+	}
+}

tweed5-serde-jackson/build.gradle.kts

@@ -8,6 +8,8 @@ dependencies {
     implementation(project(":tweed5-serde-api"))
 	implementation(libs.jackson.core)
 	shadowOnly(libs.jackson.core)
+
+	testImplementation(project(":serde-json-test-utils"))
 }
 
 tasks.shadowJar {

tweed5-serde-jackson/src/test/java/de/siphalor/tweed5/data/jackson/JacksonReaderTest.java

@@ -2,77 +2,21 @@ package de.siphalor.tweed5.data.jackson;
 
 import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.StreamReadFeature;
+import de.siphalor.tweed5.dataapi.api.TweedDataReader;
+import de.siphalor.tweed5.testutils.serde.json.JsonReaderTest;
 import lombok.SneakyThrows;
-import org.junit.jupiter.api.Test;
 
 import java.io.ByteArrayInputStream;
 import java.nio.charset.StandardCharsets;
 
-import static org.assertj.core.api.Assertions.assertThat;
+class JacksonReaderTest implements JsonReaderTest {
-
-class JacksonReaderTest {
 	@SneakyThrows
-	@Test
+	@Override
-	void complex() {
+	public TweedDataReader createJsonReader(String text) {
-		var inputStream = new ByteArrayInputStream("""
+		var parser = JsonFactory.builder()
-				{
+				.enable(StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION)
-					"first": [
+				.build()
-						[ 1 ]
+				.createParser(new ByteArrayInputStream(text.getBytes(StandardCharsets.UTF_8)));
-					],
+		return new JacksonReader(parser);
-					"second": {
-						"test": "Hello World!"
-					}
-				}
-				""".getBytes(StandardCharsets.UTF_8));
-		try (var parser = JsonFactory.builder().enable(StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION).build().createParser(inputStream)) {
-			var reader = new JacksonReader(parser);
-
-			var token = reader.peekToken();
-			assertThat(token.isMapStart()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapStart()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapEntryKey()).isTrue();
-			assertThat(token.canReadAsString()).isTrue();
-			assertThat(token.readAsString()).isEqualTo("first");
-			token = reader.readToken();
-			assertThat(token.isMapEntryValue()).isTrue();
-			assertThat(token.isListStart()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapEntryValue()).isFalse();
-			assertThat(token.isListValue()).isTrue();
-			assertThat(token.isListStart()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isListValue()).isTrue();
-			assertThat(token.canReadAsInt()).isTrue();
-			assertThat(token.readAsInt()).isEqualTo(1);
-			token = reader.readToken();
-			assertThat(token.isListValue()).isTrue();
-			assertThat(token.isListEnd()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isListValue()).isFalse();
-			assertThat(token.isMapEntryValue()).isTrue();
-			assertThat(token.isListEnd()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapEntryKey()).isTrue();
-			assertThat(token.canReadAsString()).isTrue();
-			assertThat(token.readAsString()).isEqualTo("second");
-			token = reader.readToken();
-			assertThat(token.isMapEntryValue()).isTrue();
-			assertThat(token.isMapStart()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapEntryValue()).isFalse();
-			assertThat(token.isMapEntryKey()).isTrue();
-			assertThat(token.canReadAsString()).isTrue();
-			assertThat(token.readAsString()).isEqualTo("test");
-			token = reader.readToken();
-			assertThat(token.isMapEntryValue()).isTrue();
-			assertThat(token.canReadAsString()).isTrue();
-			assertThat(token.readAsString()).isEqualTo("Hello World!");
-			token = reader.readToken();
-			assertThat(token.isMapEnd()).isTrue();
-			token = reader.readToken();
-			assertThat(token.isMapEnd()).isTrue();
-		}
 	}
 }