[Java] Unalias type when generating default value for model property (#5017)

Co-authored-by: Jim Schubert <james.schubert@gmail.com>

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

@@ -24,6 +24,7 @@ import io.swagger.v3.oas.models.PathItem;
 import io.swagger.v3.oas.models.media.ArraySchema;
 import io.swagger.v3.oas.models.media.ComposedSchema;
 import io.swagger.v3.oas.models.media.Schema;
+import io.swagger.v3.oas.models.media.StringSchema;
 import io.swagger.v3.oas.models.servers.Server;
 import io.swagger.v3.parser.util.SchemaTypeUtil;
 import org.apache.commons.io.FilenameUtils;
@@ -765,16 +766,23 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
 
     @Override
     public String getTypeDeclaration(Schema p) {
-        if (ModelUtils.isArraySchema(p)) {
+        Schema<?> schema = ModelUtils.unaliasSchema(this.openAPI, p);
-            Schema<?> items = getSchemaItems((ArraySchema) p);
+        Schema<?> target = ModelUtils.isGenerateAliasAsModel() ? p : schema;
-            return getSchemaType(p) + "<" + getTypeDeclaration(ModelUtils.unaliasSchema(this.openAPI, items)) + ">";
+        if (ModelUtils.isArraySchema(target)) {
-        } else if (ModelUtils.isMapSchema(p) && !ModelUtils.isComposedSchema(p)) {
+            Schema<?> items = getSchemaItems((ArraySchema) schema);
+            return getSchemaType(target) + "<" + getTypeDeclaration(items) + ">";
+        } else if (ModelUtils.isMapSchema(target)) {
             // Note: ModelUtils.isMapSchema(p) returns true when p is a composed schema that also defines
             // additionalproperties: true
-            Schema<?> inner = getSchemaAdditionalProperties(p);
+            Schema<?> inner = getAdditionalProperties(target);
-            return getSchemaType(p) + "<String, " + getTypeDeclaration(ModelUtils.unaliasSchema(this.openAPI, inner)) + ">";
+            if (inner == null) {
+                LOGGER.error("`{}` (map property) does not have a proper inner type defined. Default to type:string", p.getName());
+                inner = new StringSchema().description("TODO default missing map inner type to string");
+                p.setAdditionalProperties(inner);
+            }
+            return getSchemaType(target) + "<String, " + getTypeDeclaration(inner) + ">";
         }
-        return super.getTypeDeclaration(p);
+        return super.getTypeDeclaration(target);
     }
 
     @Override

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/AbstractJavaCodegenTest.java

@@ -416,6 +416,34 @@ public class AbstractJavaCodegenTest {
         Schema<?> schema = createObjectSchemaWithMinItems();
         String defaultValue = codegen.toDefaultValue(schema);
         Assert.assertNull(defaultValue);
+
+        // Create an alias to an array schema
+        Schema<?> nestedArraySchema = new ArraySchema().items(new IntegerSchema().format("int32"));
+        codegen.setOpenAPI(new OpenAPI().components(new Components().addSchemas("NestedArray", nestedArraySchema)));
+
+        // Create an array schema with item type set to the array alias
+        schema = new ArraySchema().items(new Schema().$ref("#/components/schemas/NestedArray"));
+
+        ModelUtils.setGenerateAliasAsModel(false);
+        defaultValue = codegen.toDefaultValue(schema);
+        Assert.assertEquals(defaultValue, "new ArrayList<List<Integer>>()");
+
+        ModelUtils.setGenerateAliasAsModel(true);
+        defaultValue = codegen.toDefaultValue(schema);
+        Assert.assertEquals(defaultValue, "new ArrayList<NestedArray>()");
+
+        // Create a map schema with additionalProperties type set to array alias
+        schema = new MapSchema().additionalProperties(new Schema().$ref("#/components/schemas/NestedArray"));
+
+        ModelUtils.setGenerateAliasAsModel(false);
+        defaultValue = codegen.toDefaultValue(schema);
+        Assert.assertEquals(defaultValue, "new HashMap<String, List<Integer>>()");
+
+        ModelUtils.setGenerateAliasAsModel(true);
+        defaultValue = codegen.toDefaultValue(schema);
+        Assert.assertEquals(defaultValue, "new HashMap<String, NestedArray>()");
+        
+        // Test default value for date format
         DateSchema dateSchema = new DateSchema();
         LocalDate defaultLocalDate = LocalDate.of(2019,2,15);
         Date date = Date.from(defaultLocalDate.atStartOfDay(ZoneId.systemDefault()).toInstant());

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java

@@ -608,6 +608,7 @@ public class JavaClientCodegenTest {
                 .setLibrary(JavaClientCodegen.RESTEASY)
                 .setAdditionalProperties(properties)
                 .setImportMappings(importMappings)
+                .setGenerateAliasAsModel(true)
                 .setInputSpec("src/test/resources/3_0/type-alias.yaml")
                 .setOutputDir(output.getAbsolutePath().replace("\\", "/"));