Test rejecting invalid charsets by JSON writer

configuration/checkstyle-rules.xml

@@ -169,7 +169,9 @@
 
 		<!-- Size Violations -->
 
-		<module name=" AnonInnerLength " />
+		<module name=" AnonInnerLength">
+			<property name="max" value="25" />
+		</module>
 		<module name="MethodLength">
 			<property name="max" value="200" />
 		</module>

tinylog-impl/src/test/java/org/tinylog/util/CustomTestCharset.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package org.tinylog.util;
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.CoderResult;
+
+/**
+ * Custom charset that can read and write all ASCII characters. One defined character will be doubled to two bytes
+ * instead of one for testing different lengths for characters.
+ */
+public class CustomTestCharset extends Charset {
+
+	private final char longCharacter;
+
+	/**
+	 * @param longCharacter This character will take two bytes instead of one
+	 */
+	public CustomTestCharset(final char longCharacter) {
+		super(String.format("CUSTOM-TEST-CHARSET-%02X", (short) longCharacter), new String[0]);
+		this.longCharacter = longCharacter;
+	}
+
+	@Override
+	public boolean contains(final Charset charset) {
+		return false;
+	}
+
+	@Override
+	public CharsetDecoder newDecoder() {
+		return new CharsetDecoder(this, 1, 2) {
+			@Override
+			protected CoderResult decodeLoop(final ByteBuffer in, final CharBuffer out) {
+				while (in.hasRemaining()) {
+					if (!out.hasRemaining()) {
+						return CoderResult.OVERFLOW;
+					}
+
+					byte character = in.get();
+
+					if (character == longCharacter) {
+						if (in.hasRemaining()) {
+							character = in.get();
+						} else {
+							in.position(in.position() - 1);
+							return CoderResult.UNDERFLOW;
+						}
+					}
+
+					out.put((char) character);
+				}
+
+				return CoderResult.UNDERFLOW;
+			}
+		};
+	}
+
+	@Override
+	public CharsetEncoder newEncoder() {
+		return new CharsetEncoder(this, 1, 2) {
+			@Override
+			protected CoderResult encodeLoop(final CharBuffer in, final ByteBuffer out) {
+				while (in.hasRemaining()) {
+					char character = in.get();
+					int length = character == longCharacter ? 2 : 1;
+
+					if (out.remaining() < length) {
+						in.position(in.position() - 1);
+						return CoderResult.OVERFLOW;
+					}
+
+					for (int i = 0; i < length; ++i) {
+						out.put((byte) character);
+					}
+				}
+
+				return CoderResult.UNDERFLOW;
+			}
+		};
+	}
+
+}

tinylog-impl/src/test/java/org/tinylog/util/CustomTestCharsetProvider.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2021 Martin Winandy
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package org.tinylog.util;
+
+import java.nio.charset.Charset;
+import java.nio.charset.spi.CharsetProvider;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.tinylog.writers.JsonWriterTest;
+
+/**
+ * Service factory for {@link CustomTestCharset}.
+ */
+public class CustomTestCharsetProvider extends CharsetProvider {
+
+	/**
+	 * All required charsets for {@link JsonWriterTest.IllegalCharsetTest}.
+	 */
+	public static final List<Charset> CHARSETS = Stream.of('\n', '\r', ' ', '\t', ',', '[', ']')
+			.map(CustomTestCharset::new)
+			.collect(Collectors.toList());
+
+	/** */
+	public CustomTestCharsetProvider() {
+	}
+
+	@Override
+	public Iterator<Charset> charsets() {
+		return CHARSETS.iterator();
+	}
+
+	@Override
+	public Charset charsetForName(final String charsetName) {
+		return CHARSETS.stream()
+			.filter(charset -> Objects.equals(charsetName, charset.name()))
+			.findFirst()
+			.orElse(null);
+	}
+
+}

tinylog-impl/src/test/java/org/tinylog/writers/JsonWriterTest.java

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 import org.junit.Rule;
 import org.junit.Test;
@@ -33,6 +34,7 @@
 import org.tinylog.core.LogEntryValue;
 import org.tinylog.core.TinylogLoggingProviderTest.LogEntryValues;
 import org.tinylog.rules.SystemStreamCollector;
+import org.tinylog.util.CustomTestCharsetProvider;
 import org.tinylog.util.FileSystem;
 import org.tinylog.util.LogEntryBuilder;
 
@@ -444,4 +446,50 @@ public void handlesInvalidCharset() throws IOException {
 
 	}
 
+	/**
+	 * Tests for illegal charset validation.
+	 */
+	@RunWith(Parameterized.class)
+	public static class IllegalCharsetTest {
+
+		/**
+		 * Redirects and collects system output streams.
+		 */
+		@Rule
+		public final SystemStreamCollector systemStream = new SystemStreamCollector(true);
+
+		private final Charset charset;
+
+		/**
+		 * @param charset The illegal charset to validate
+		 */
+		public IllegalCharsetTest(final Charset charset) {
+			this.charset = charset;
+		}
+
+		/**
+		 * Returns illegal charsets that should be tested.
+		 *
+		 * @return Each object array contains a single charset
+		 */
+		@Parameterized.Parameters(name = "{0}")
+		public static Collection<Object[]> getSizes() {
+			return CustomTestCharsetProvider.CHARSETS.stream()
+				.map(charset -> new Object[] {charset})
+				.collect(Collectors.toList());
+		}
+
+		@Test
+		public void validateCharset() throws IOException {
+			Map<String, String> properties = new HashMap<>();
+			properties.put("file", FileSystem.createTemporaryFile());
+			properties.put("charset", charset.name());
+
+			assertThatCode(() -> new JsonWriter(properties))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessageContaining(charset.name());
+		}
+
+	}
+
 }

tinylog-impl/src/test/resources/META-INF/services/java.nio.charset.spi.CharsetProvider

@@ -0,0 +1 @@
+org.tinylog.util.CustomTestCharsetProvider