Fix #106: convert optional collections to IDL

build.gradle.kts

@@ -68,6 +68,8 @@ intellij {
 	//version.set("2022.3.2")
 	//version.set("2022.3.3")
 	//version.set("2023.1")
+	//version.set("2023.2")
+	//version.set("2023.2.1")
 
 	// Note: without the java plugin tests will fail (so don't remove it even if the plugin does not need it)
 	plugins.set(listOf("com.intellij.java"))
@@ -121,6 +123,7 @@ tasks {
 			<ul data-version="213.5.3">
 				<li>Improved grammar (string literal syntax)</li>
 				<li>Implemented better symbols (adds symbol search)</li>
+				<li>Fix #106: converting to IDL now handles optional collections correctly
 			</ul>
 			<p>Version 213.5.2:</p>
 			<ul data-version="213.5.2">
@@ -133,7 +136,7 @@ tasks {
 			<ul data-version="213.5.1">
 				<li>Upgraded dependencies</li>
 			</ul>
-			""";
+			"""
 		changeLog += """
 			<p>Version 213.5.0:</p>
 			<ul data-version="213.5.0">
@@ -144,7 +147,7 @@ tasks {
 			</li>
 			<li>Added disposed check in menu actions (issue #73)</li>
 			</ul>
-			""";
+			"""
 		changeLog += """
 			<p>Version 213.4.3:</p>
 			<ul data-version="213.4.3">
@@ -166,7 +169,7 @@ tasks {
 			<li>Implement #42: Renaming a schema or field now adds an alias for the old name</li>
 			<li>Add new settings for #42, making the behaviour congigurable (by default, only fields receive an alias)</li>
 			</ul>
-			""";
+			"""
 		//changeLog += """
 		//	<p>Version 213.3.1:</p>
 		//	<ul data-version="213.3.1">
@@ -179,7 +182,7 @@ tasks {
 		//	<li>Fix #37 (generating IDL can yield invalid names with Avro <= 1.11.0)</li>
 		//	<li>Added error report submitter (submit crash reports directly to GitHub)</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 213.2.1:</p>
 		//	<ul data-version="213.2.1">
@@ -192,7 +195,7 @@ tasks {
 		//	<li>Added support for Kotlin style nullable types (new in Avro 1.11.1)</li>
 		//	<li>Added inspection for documentation comments to detect and apply fixes for improvements since Avro 1.11.1</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 213.1.0:</p>
 		//	<ul data-version="213.1.0">
@@ -202,7 +205,7 @@ tasks {
 		//	<li>Improved brace handling</li>
 		//	<li>Improved references to schemata in JSON (<code>.avsc</code>/<code>.avpr</code>)</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 213.0.1:</p>
 		//	<ul data-version="213.0.1">
@@ -217,7 +220,7 @@ tasks {
 		//	<li>Improved quote & brace handling: now supports all "", {}, [] and <> pairs</li>
 		//	<li>Using IntelliJ version 2021.3 to test</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 203.1.2:</p>
 		//	<ul data-version="203.1.2">
@@ -239,7 +242,7 @@ tasks {
 		//	<li>Adjusted IDL parsing to allow dangling doc comments</li>
 		//	<li>Added warnings for dangling doc comments (the Avro IDL compiler ignores these)</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 203.0.3:</p>
 		//	<ul data-version="203.0.3">
@@ -261,7 +264,7 @@ tasks {
 		//	<li>Added refactoring actions to convert Avro IDL to and from Avro schemas and Avro protocols.</li>
 		//	<li>Added file icon variant for dark mode</li>
 		//	</ul>
-		//	""";
+		//	"""
 		//changeLog += """
 		//	<p>Version 0.2.1:</p>
 		//	<ul data-version="0.2.1">

src/main/java/opwvhk/intellij/avro_idl/actions/IdlUtils.java

@@ -30,6 +30,8 @@ public final class IdlUtils {
 			"idl", "import", "int", "local_timestamp_ms", "long", "map", "namespace", "null", "oneway", "protocol",
 			"record", "schema", "string", "throws",
 			"timestamp_ms", "time_ms", "true", "union", "uuid", "void");
+	private static final EnumSet<Schema.Type> NULLABLE_TYPES = EnumSet.complementOf(
+			EnumSet.of(Schema.Type.ARRAY, Schema.Type.MAP, Schema.Type.UNION));
 
 	static {
 		SCHEMA_FACTORY = getFieldValue(getField(Schema.class, "FACTORY"), null);
@@ -337,13 +339,13 @@ private static void writeFieldSchema(Schema schema, Writer writer, JsonGenerator
 			writer.append('>');
 		} else if (type == Schema.Type.UNION) {
 			// Note: unions cannot have properties
-			List<Schema> types = schema.getTypes();
-			if (schema.isNullable() && types.size() == 2) {
-				Schema nonNullSchema = !types.get(0).isNullable() ? types.get(0) : types.get(1);
-				writeFieldSchema(nonNullSchema, writer, jsonGen, alreadyDeclared, toDeclare, recordNameSpace);
+			Schema schemaForNullableSyntax = getNullableUnionType(schema);
+			if (schemaForNullableSyntax != null) {
+				writeFieldSchema(schemaForNullableSyntax, writer, jsonGen, alreadyDeclared, toDeclare, recordNameSpace);
 				writer.append('?');
 			} else {
 				writer.append("union{");
+				List<Schema> types = schema.getTypes();
 				Iterator<Schema> iterator = types.iterator();
 				if (iterator.hasNext()) {
 					writeFieldSchema(iterator.next(), writer, jsonGen, alreadyDeclared, toDeclare, recordNameSpace);
@@ -387,6 +389,23 @@ private static void writeFieldSchema(Schema schema, Writer writer, JsonGenerator
 		}
 	}
 
+	/**
+	 * Get the type from a nullable 2-type union if that type is eligible for the '?'-syntax.
+	 *
+	 * @param unionSchema a union schema
+	 * @return the non-null schema in a nullable 2-type union iff not a container
+	 */
+	private static Schema getNullableUnionType(Schema unionSchema) {
+		List<Schema> types = unionSchema.getTypes();
+		if (unionSchema.isNullable() && types.size() == 2) {
+			Schema nonNullSchema = !types.get(0).isNullable() ? types.get(0) : types.get(1);
+			if (NULLABLE_TYPES.contains(nonNullSchema.getType())) {
+				return nonNullSchema;
+			}
+		}
+		return null;
+	}
+
 	private static void writeSchemaAttributes(Schema schema, Writer writer, JsonGenerator jsonGen) throws IOException {
 		writeDocumentation(writer, "    ", schema.getDoc());
 		writeJsonProperties(schema, writer, jsonGen, "    ");

src/test/resources/opwvhk/intellij/avro_idl/actions/idl_utils_test_protocol.avdl

@@ -10,7 +10,7 @@ protocol HappyFlow {
         @my-key("my-value") map<common.Flag> @order("DESCENDING") flags;
         Counter mainCounter;
         /** A list of counters. */
-        @my-key("my-value") array<Counter> otherCounters = [];
+        union{null, @my-key("my-value") array<Counter>} otherCounters = null;
         Nonce nonce;
         date my_date;
         time_ms my_time;

src/test/resources/opwvhk/intellij/avro_idl/actions/idl_utils_test_schema.avdl

@@ -9,7 +9,7 @@ protocol HappyFlow {
         @my-key("my-value") map<common.Flag> @order("DESCENDING") flags;
         Counter mainCounter;
         /** A list of counters. */
-        @my-key("my-value") array<Counter> otherCounters = [];
+        union{null, @my-key("my-value") array<Counter>} otherCounters = null;
         Nonce nonce;
         date my_date;
         time_ms my_time;