fix discriminator model lookup when used with model name suffix (#23363)

Author: hrach

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

@@ -76,18 +76,27 @@ public static class MappedModel implements Comparable<MappedModel> {
         // is converted to a sanitized, internal representation within codegen.
         @Getter @Setter
         private String modelName;
+        // The raw schema name as it appears in the OAS document, before any
+        // modelNamePrefix/Suffix transformation.
+        @Getter
+        private String schemaName;
 
         @Getter @Setter
         private CodegenModel model;
 
         private final boolean explicitMapping;
 
-        public MappedModel(String mappingName, String modelName, boolean explicitMapping) {
+        public MappedModel(String mappingName, String modelName, String schemaName, boolean explicitMapping) {
             this.mappingName = mappingName;
             this.modelName = modelName;
+            this.schemaName = schemaName;
             this.explicitMapping = explicitMapping;
         }
 
+        public MappedModel(String mappingName, String modelName, boolean explicitMapping) {
+            this(mappingName, modelName, null, explicitMapping);
+        }
+
         public boolean isExplicitMapping() {
             return explicitMapping;
         }

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

@@ -507,7 +507,8 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
             // add the model to the discriminator's mapping so templates have access to more than just the string to string mapping
             if (model.discriminator != null && model.discriminator.getMappedModels() != null) {
                 for (CodegenDiscriminator.MappedModel mappedModel : model.discriminator.getMappedModels()) {
-                    CodegenModel mappedCodegenModel = ModelUtils.getModelByName(mappedModel.getModelName(), objs);
+                    String lookupName = mappedModel.getSchemaName() != null ? mappedModel.getSchemaName() : mappedModel.getModelName();
+                    CodegenModel mappedCodegenModel = ModelUtils.getModelByName(lookupName, objs);
                     mappedModel.setModel(mappedCodegenModel);
                 }
             }
@@ -3574,7 +3575,7 @@ protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName,
                     once(LOGGER).warn("'{}' defines discriminator '{}', but the referenced schema '{}' is incorrect. {}",
                             composedSchemaName, discPropName, modelName, msgSuffix);
                 }
-                MappedModel mm = new MappedModel(modelName, toModelName(modelName));
+                MappedModel mm = new MappedModel(modelName, toModelName(modelName), modelName, false);
                 descendentSchemas.add(mm);
                 Schema cs = ModelUtils.getSchema(openAPI, modelName);
                 if (cs == null) { // cannot lookup the model based on the name
@@ -3583,7 +3584,7 @@ protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName,
                     Map<String, Object> vendorExtensions = cs.getExtensions();
                     if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey(X_DISCRIMINATOR_VALUE)) {
                         String xDiscriminatorValue = (String) vendorExtensions.get(X_DISCRIMINATOR_VALUE);
-                        mm = new MappedModel(xDiscriminatorValue, toModelName(modelName), true);
+                        mm = new MappedModel(xDiscriminatorValue, toModelName(modelName), modelName, true);
                         descendentSchemas.add(mm);
                     }
                 }
@@ -3641,7 +3642,7 @@ protected List<MappedModel> getAllOfDescendants(String thisSchemaName) {
                             .map(ve -> ve.get(X_DISCRIMINATOR_VALUE))
                             .map(discriminatorValue -> (String) discriminatorValue)
                             .orElse(currentSchemaName);
-            MappedModel mm = new MappedModel(mappingName, toModelName(currentSchemaName), !mappingName.equals(currentSchemaName));
+            MappedModel mm = new MappedModel(mappingName, toModelName(currentSchemaName), currentSchemaName, !mappingName.equals(currentSchemaName));
             descendentSchemas.add(mm);
         }
         return descendentSchemas;
@@ -3687,7 +3688,7 @@ protected CodegenDiscriminator createDiscriminator(String schemaName, Schema sch
                 } else {
                     name = e.getValue();
                 }
-                uniqueDescendants.add(new MappedModel(e.getKey(), toModelName(name), true));
+                uniqueDescendants.add(new MappedModel(e.getKey(), toModelName(name), name, true));
             }
         }
 

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

@@ -1680,6 +1680,47 @@ public void testComposedSchemaOneOfDiscriminatorMapPreAndPostFix() {
         assertThat(cm.discriminator.getPropertyType()).isEqualTo("TransferFruitTypeEnumDto");
     }
 
+    @Test
+    public void testDiscriminatorMappedModelWithModelNameSuffix() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+        codegen.setModelNameSuffix("Dto");
+
+        // Build allProcessedModels map keyed by raw schema name (as DefaultGenerator does)
+        Map<String, ModelsMap> allProcessedModels = new TreeMap<>();
+        String[] schemaNames = {"FruitReqDisc", "AppleReqDisc", "BananaReqDisc"};
+        for (String name : schemaNames) {
+            Schema schema = openAPI.getComponents().getSchemas().get(name);
+            CodegenModel cm = codegen.fromModel(name, schema);
+            ModelMap mo = new ModelMap();
+            mo.setModel(cm);
+            ModelsMap models = new ModelsMap();
+            models.setModels(Collections.singletonList(mo));
+            allProcessedModels.put(name, models);
+        }
+
+        // Verify schemaName is stored and differs from modelName
+        CodegenModel fruitModel = ModelUtils.getModelByName("FruitReqDisc", allProcessedModels);
+        assertNotNull(fruitModel.discriminator);
+        for (CodegenDiscriminator.MappedModel mm : fruitModel.discriminator.getMappedModels()) {
+            assertNotNull(mm.getSchemaName(),
+                    "MappedModel.getSchemaName() should not be null for " + mm.getModelName());
+            assertNotEquals(mm.getSchemaName(), mm.getModelName(),
+                    "schemaName should differ from modelName when modelNameSuffix is set");
+        }
+
+        // Verify postProcessAllModels resolves MappedModel.model via schemaName
+        Map<String, ModelsMap> result = codegen.postProcessAllModels(allProcessedModels);
+        fruitModel = ModelUtils.getModelByName("FruitReqDisc", result);
+        for (CodegenDiscriminator.MappedModel mm : fruitModel.discriminator.getMappedModels()) {
+            assertNotNull(mm.getModel(),
+                    "MappedModel.getModel() should not be null for " + mm.getModelName()
+                            + " (mappingName=" + mm.getMappingName() + ")");
+        }
+    }
+
     @Test
     public void testComposedSchemaMyPetsOneOfDiscriminatorMap() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");