normalizer REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING

docs/customization.md

@@ -651,6 +651,13 @@ Example:
 java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g java -i modules/openapi-generator/src/test/resources/3_0/required-properties.yaml -o /tmp/java-okhttp/ --openapi-normalizer REMOVE_PROPERTIES_FROM_TYPE_OTHER_THAN_OBJECT=true
 ```
 
+- `REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING``: when set to true, oneOf is removed and is converted into mappings in a discriminator mapping.
+
+Example:
+```
+java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g spring -i modules/openapi-generator/src/test/resources/3_0/spring/issue_23527.yaml -o /tmp/java-spring/ --openapi-normalizer REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING=true
+```
+
 - `FILTER`
 
 The `FILTER` parameter allows selective inclusion of API operations based on specific criteria. It applies the `x-internal: true` property to operations that do **not** match the specified values, preventing them from being generated. Multiple filters can be separated by a semicolon.

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

@@ -78,6 +78,10 @@ public class OpenAPINormalizer {
     // are removed as most generators cannot handle such case at the moment
     final String REMOVE_ANYOF_ONEOF_AND_KEEP_PROPERTIES_ONLY = "REMOVE_ANYOF_ONEOF_AND_KEEP_PROPERTIES_ONLY";
 
+    // when set to true, oneOf is removed and is converted into mappings in a discriminator mapping
+    final String REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING = "REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING";
+
+
     // when set to true, oneOf/anyOf with either string or enum string as sub schemas will be simplified
     // to just string
     final String SIMPLIFY_ANYOF_STRING_AND_ENUM_STRING = "SIMPLIFY_ANYOF_STRING_AND_ENUM_STRING";
@@ -214,6 +218,7 @@ public OpenAPINormalizer(OpenAPI openAPI, Map<String, String> inputRules) {
         ruleNames.add(SIMPLIFY_ONEOF_ANYOF_ENUM);
         ruleNames.add(REMOVE_PROPERTIES_FROM_TYPE_OTHER_THAN_OBJECT);
         ruleNames.add(SORT_MODEL_PROPERTIES);
+        ruleNames.add(REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING);
 
         // rules that are default to true
         rules.put(SIMPLIFY_ONEOF_ANYOF, true);
@@ -1053,6 +1058,8 @@ protected Schema normalizeOneOf(Schema schema, Set<Schema> visitedSchemas) {
         // simplify first as the schema may no longer be a oneOf after processing the rule below
         schema = processSimplifyOneOf(schema);
 
+        schema = processReplaceOneOfByMapping(schema);
+
         // if it's still a oneOf, loop through the sub-schemas
         if (schema.getOneOf() != null) {
             for (int i = 0; i < schema.getOneOf().size(); i++) {
@@ -1569,6 +1576,33 @@ protected Schema processSimplifyOneOf(Schema schema) {
         return schema;
     }
 
+
+    protected Schema processReplaceOneOfByMapping(Schema schema) {
+        if (!getRule(REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING)) {
+            return schema;
+        }
+
+        if (schema.getDiscriminator() != null) {
+            Discriminator discriminator = schema.getDiscriminator();
+            if (discriminator.getMapping() == null) {
+                Map<String, String> mapping = new TreeMap<>();
+                discriminator.setMapping(mapping);
+                for (Object oneOfObject : schema.getOneOf()) {
+                    Schema oneOf = (Schema) oneOfObject;
+                    String ref = oneOf.get$ref();
+                    if (ref != null) {
+                        String name = ref.contains("/") ? ref.substring(ref.lastIndexOf('/') + 1) : ref;
+                        mapping.put(name, oneOf.get$ref());
+                    }
+                }
+            }
+
+            schema.setOneOf(null);
+        }
+        return schema;
+    }
+
+
     /**
      * Set nullable to true in array/set if needed.
      *

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

@@ -16,6 +16,9 @@
 
 package org.openapitools.codegen;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import io.swagger.util.Yaml;
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
 import io.swagger.v3.oas.models.PathItem;
@@ -1502,4 +1505,29 @@ public Schema normalizeSchema(Schema schema, Set<Schema> visitedSchemas) {
         }
     }
 
+    @Test
+    public void testREPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING() {
+        // to test array schema processing in 3.1 spec
+        OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0/spring/issue_23527.yaml");
+
+        Map<String, String> inputRules = Map.of("REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING", "true");
+        OpenAPINormalizer openAPINormalizer = new OpenAPINormalizer(openAPI, inputRules);
+        openAPINormalizer.normalize();
+        dump(openAPI);
+    }
+
+    private void dump(OpenAPI openAPI) {
+
+        ObjectMapper mapper = Yaml.mapper();
+        String yaml = null;
+        try {
+            yaml = mapper.writeValueAsString(openAPI);
+        } catch (JsonProcessingException e) {
+            throw new RuntimeException(e);
+        }
+
+        System.out.println(yaml);
+
+    }
+
 }

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

@@ -72,6 +72,7 @@
 import static org.openapitools.codegen.CodegenConstants.*;
 import static org.openapitools.codegen.TestUtils.*;
 import static org.openapitools.codegen.languages.JavaClientCodegen.*;
+import static org.openapitools.codegen.languages.SpringCodegen.SPRING_BOOT;
 import static org.testng.Assert.*;
 
 public class JavaClientCodegenTest {
@@ -4325,4 +4326,33 @@ public void testJspecify(String library, boolean useSpringBoot4, boolean hasJspe
                 .fileContains("@org.jspecify.annotations.NullMarked");
 
     }
+
+    @DataProvider(name = "replaceOneOf")
+    public Object[][] replaceOneOf() {
+        return new Object[][]{
+                {"src/test/resources/3_0/spring/issue_23527.yaml"},
+                {"src/test/resources/3_0/spring/issue_23527_1.yaml"},
+                {"src/test/resources/3_0/spring/issue_23527_2.yaml"}
+        };
+    }
+
+    @Test(dataProvider = "replaceOneOf" )
+    void replaceOneOfByDiscriminatorMapping(String file) throws IOException {
+        Map<String, File> files = generateFromContract(file, APACHE, Map.of(),
+                codegen -> codegen.addOpenapiNormalizer("REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING", "true"));
+
+        JavaFileAssert.assertThat(files.get("GeoJsonObject.java"))
+                .isNormalClass()
+                .doesNotExtendsClasses()
+                .fileContains("String type")
+                .fileDoesNotContain("coordinates")
+                .assertTypeAnnotations()
+                .containsWithName("JsonSubTypes");
+
+        JavaFileAssert.assertThat(files.get("Polygon.java"))
+                .extendsClass("GeoJsonObject")
+                .doesNotImplementInterfaces("GeoJsonObject")
+                .fileContains("List<Double> coordinates");
+
+    }
 }

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

@@ -59,6 +59,36 @@ public JavaFileAssert isNormalClass() {
         return this;
     }
 
+    public JavaFileAssert extendsClass(String... parentClass) {
+        Set<String> expectedClasses = Stream.of(parentClass)
+                .collect(Collectors.toSet());
+
+        Set<String> actualParents = actual.getType(0)
+                .asClassOrInterfaceDeclaration().getExtendedTypes()
+                .stream()
+                .map(ClassOrInterfaceType::getNameWithScope)
+                .collect(Collectors.toSet());
+
+        Assertions.assertThat(actualParents)
+                .withFailMessage("Expected type %s to extends %s, but found %s",
+                        actual.getType(0).getName().asString(), expectedClasses, actualParents)
+                .isEqualTo(expectedClasses);
+        return this;
+    }
+
+    public JavaFileAssert doesNotExtendsClasses() {
+        Set<String> actualParents = actual.getType(0)
+                .asClassOrInterfaceDeclaration().getExtendedTypes()
+                .stream()
+                .map(ClassOrInterfaceType::getNameWithScope)
+                .collect(Collectors.toSet());
+        Assertions.assertThat(actualParents)
+                .withFailMessage("Expected type %s to extends a class, but found %s",
+                        actual.getType(0).getName().asString(), actualParents)
+                .isEmpty();
+        return this;
+    }
+
     public JavaFileAssert implementsInterfaces(String... implementedInterfaces) {
         Set<String> expectedInterfaces = Stream.of(implementedInterfaces)
                 .collect(Collectors.toSet());

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

@@ -6664,4 +6664,35 @@ public void testJspecify(String library, int springBootVersion, String fooApiFil
         JavaFileAssert.assertThat(files.get("model/package-info.java"))
                 .fileContains("@org.jspecify.annotations.NullMarked");
     }
+
+
+    @DataProvider(name = "replaceOneOf")
+    public Object[][] replaceOneOf() {
+        return new Object[][]{
+                {"src/test/resources/3_0/spring/issue_23527.yaml"},
+                {"src/test/resources/3_0/spring/issue_23527_1.yaml"},
+                {"src/test/resources/3_0/spring/issue_23527_2.yaml"}
+        };
+    }
+
+    @Test(dataProvider = "replaceOneOf" )
+    void replaceOneOfByDiscriminatorMapping(String file) throws IOException {
+        Map<String, File> files = generateFromContract(file, SPRING_BOOT, Map.of(),
+                codegen -> codegen.addOpenapiNormalizer("REPLACE_ONE_OF_BY_DISCRIMINATOR_MAPPING", "true"));
+
+        JavaFileAssert.assertThat(files.get("GeoJsonObject.java"))
+                .isNormalClass()
+                .doesNotExtendsClasses()
+                .fileContains("String type")
+                .fileDoesNotContain("coordinates")
+                .assertTypeAnnotations()
+                .containsWithName("JsonSubTypes")
+        ;
+
+        JavaFileAssert.assertThat(files.get("Polygon.java"))
+                .extendsClass("GeoJsonObject")
+                .doesNotImplementInterfaces("GeoJsonObject")
+                .fileContains("List<Double> coordinates");
+
+    }
 }

modules/openapi-generator/src/test/resources/3_0/spring/issue_23527.yaml

@@ -0,0 +1,41 @@
+openapi: 3.0.3
+info:
+  title: GeoJSON Discriminator Test
+  version: 1.0.0
+paths: {}
+components:
+  schemas:
+    GeoJsonObject:
+      type: object
+      properties:
+        type:
+          type: string
+      required:
+        - type
+      discriminator:
+        propertyName: type
+      oneOf:
+        - $ref: '#/components/schemas/Polygon'
+        - $ref: '#/components/schemas/MultiPolygon'
+    Polygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: number
+                format: double
+    MultiPolygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: array
+                items:
+                  type: number
+                  format: double

modules/openapi-generator/src/test/resources/3_0/spring/issue_23527_1.yaml

@@ -0,0 +1,44 @@
+openapi: 3.0.3
+info:
+  title: GeoJSON Discriminator Test
+  version: 1.0.0
+paths: {}
+components:
+  schemas:
+    GeoJsonObject:
+      type: object
+      properties:
+        type:
+          type: string
+      required:
+        - type
+      discriminator:
+        propertyName: type
+        mapping:
+          Polygon: '#/components/schemas/Polygon'
+          MultiPolygon: '#/components/schemas/MultiPolygon'
+      oneOf:
+        - $ref: '#/components/schemas/Polygon'
+        - $ref: '#/components/schemas/MultiPolygon'
+    Polygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: number
+                format: double
+    MultiPolygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: array
+                items:
+                  type: number
+                  format: double

modules/openapi-generator/src/test/resources/3_0/spring/issue_23527_2.yaml

@@ -0,0 +1,41 @@
+openapi: 3.0.3
+info:
+  title: GeoJSON Discriminator Test
+  version: 1.0.0
+paths: {}
+components:
+  schemas:
+    GeoJsonObject:
+      type: object
+      properties:
+        type:
+          type: string
+      required:
+        - type
+      discriminator:
+        propertyName: type
+        mapping:
+          Polygon: '#/components/schemas/Polygon'
+          MultiPolygon: '#/components/schemas/MultiPolygon'
+    Polygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: number
+                format: double
+    MultiPolygon:
+      allOf:
+        - $ref: '#/components/schemas/GeoJsonObject'
+        - type: object
+          properties:
+            coordinates:
+              type: array
+              items:
+                type: array
+                items:
+                  type: number
+                  format: double

pom.xml

@@ -23,6 +23,15 @@
         <developerConnection>scm:git:git@github.com:openapitools/openapi-generator.git</developerConnection>
         <url>https://github.com/openapitools/openapi-generator</url>
     </scm>
+    <modules>
+        <module>modules/openapi-generator-core</module>
+        <module>modules/openapi-generator</module>
+        <module>modules/openapi-generator-cli</module>
+        <module>modules/openapi-generator-maven-plugin</module>
+        <!--                <module>modules/openapi-generator-gradle-plugin</module>-->
+        <!--                <module>modules/openapi-generator-mill-plugin</module>-->
+        <!--                <module>modules/openapi-generator-online</module>-->
+    </modules>
     <developers>
         <!-- original author of the project -->
         <developer>
@@ -408,7 +417,6 @@
                 <plugin>
                     <groupId>com.gradle</groupId>
                     <artifactId>develocity-maven-extension</artifactId>
-                    <version>${develocity-maven-extension.version}</version>
                     <configuration>
                         <develocity>
                             <normalization>
@@ -1235,7 +1243,6 @@
         <commons-io.version>2.20.0</commons-io.version>
         <commons-lang.version>3.18.0</commons-lang.version>
         <commons-text.version>1.10.0</commons-text.version>
-        <develocity-maven-extension.version>1.23.2</develocity-maven-extension.version>
         <diffutils.version>1.3.0</diffutils.version>
         <generex.version>1.0.2</generex.version>
         <git-commit-id-plugin.version>4.9.10</git-commit-id-plugin.version>