fix(protobuf-codegen): Fix protobuf import path with discriminator

This PR fixes a critical bug in the protobuf schema generator where models using discriminators with �llOf composition were generating invalid import paths when child schemas contained references to other models.

Author: Anthony TODISCO

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

@@ -139,7 +139,7 @@ public ProtobufSchemaCodegen() {
         apiTemplateFiles.put("api.mustache", ".proto");
         embeddedTemplateDir = templateDir = "protobuf-schema";
         hideGenerationTimestamp = Boolean.TRUE;
-        modelPackage = "models";
+        super.setModelPackage("models");
         apiPackage = "services";
 
         defaultIncludes = new HashSet<>(
@@ -749,9 +749,11 @@ public void addImport(Map<String, ModelsMap> objs, CodegenModel cm, String impor
         String modelFileName = this.toModelFilename(importValue);
         boolean skipImport = isImportAlreadyPresentInModel(objs, cm, modelFileName);
         if (!skipImport) {
-            this.addImport(cm, importValue);
+            // Use toModelImport to get the correct import path with model package prefix
+            String processedImport = this.toModelImport(importValue);
+            this.addImport(cm, processedImport);
             Map<String, String> importItem = new HashMap<>();
-            importItem.put(IMPORT, modelFileName);
+            importItem.put(IMPORT, processedImport);
             objs.get(cm.getName()).getImports().add(importItem);
         }
     }
@@ -1041,6 +1043,11 @@ public String toModelImport(String name) {
         if ("".equals(modelPackage())) {
             return name;
         } else {
+            // Check if the name already starts with the model package path to avoid duplication
+            String modelPath = modelPackage() + "/";
+            if (name.startsWith(modelPath)) {
+                return name;
+            }
             return modelPackage() + "/" + underscore(name);
         }
     }

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

@@ -296,4 +296,41 @@ public void unspecifiedEnumValuesIgnoredIfAlreadyPresent() {
         Assert.assertEquals(enumVars1.get(1).get("value"), "FOO");
         Assert.assertEquals(enumVars1.get(1).get("isString"), false);
     }
+
+    @Test(description = "Support multiple level of inheritance for discriminator - ensures properties from indirect children are included")
+    public void testCodeGenWithAllOfDiscriminatorMultipleLevels() throws IOException {
+        // set line break to \n across all platforms
+        System.setProperty("line.separator", "\n");
+
+        File output = Files.createTempDirectory("test").toFile();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("protobuf-schema")
+                .setInputSpec("src/test/resources/3_0/allOf_composition_discriminator_multiple_inheritance.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        TestUtils.ensureContainsFile(files, output, "models/animal.proto");
+        Path path = Paths.get(output + "/models/animal.proto");
+
+        // Verify the generated file contains all expected properties from multi-level inheritance
+        String generatedContent = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);
+        
+        // Properties from discriminated classes should be included:
+        // From Dog (direct child): bark
+        Assert.assertTrue(generatedContent.contains("string bark"), "Animal should contain 'bark' property from Dog");
+        // From Feline (direct child): name, furColor  
+        Assert.assertTrue(generatedContent.contains("string name"), "Animal should contain 'name' property from Feline");
+        Assert.assertTrue(generatedContent.contains("string fur_color"), "Animal should contain 'fur_color' property from Feline");
+        // From Cat (indirect child through Feline): isIndoor, careDetails
+        Assert.assertTrue(generatedContent.contains("bool is_indoor"), "Animal should contain 'is_indoor' property from Cat (indirect child)");
+        Assert.assertTrue(generatedContent.contains("CareDetails care_details"), "Animal should contain 'care_details' property from Cat (indirect child)");
+
+        assertFileEquals(path, Paths.get("src/test/resources/3_0/protobuf-schema/animal.proto"));
+
+        output.deleteOnExit();
+    }
 }

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

@@ -48,6 +48,8 @@ components:
           properties:
             name:
               type: string
+            characteristics:
+              $ref: '#/components/schemas/Characteristics'
     Reptile:
       allOf:
         - $ref: '#/components/schemas/Pet'

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

@@ -0,0 +1,58 @@
+openapi: 3.0.3
+info:
+  title: OAI Specification example for Polymorphism
+  version: 1.0.0
+paths:
+  /status:
+    get:
+      responses:
+        '201':
+          description: desc
+
+components:
+  schemas:
+    Animal:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+        mapping:
+          dog: '#/components/schemas/Dog'
+          cat: '#/components/schemas/Cat'
+    Feline:
+      allOf:
+        - $ref: '#/components/schemas/Animal'
+        - type: object
+          properties:
+            name:
+              type: string
+            furColor:
+              type: string
+    Cat:
+      allOf:
+        - $ref: '#/components/schemas/Feline'
+        - type: object
+          properties:
+            isIndoor:
+              type: boolean
+            careDetails:
+              $ref: '#/components/schemas/CareDetails'
+    Dog:
+      allOf:
+        - $ref: '#/components/schemas/Animal'
+        - type: object
+          properties:
+            bark:
+              type: string
+    CareDetails:
+      type: object
+      properties:
+        veterinarian:
+          type: string
+        lastVetVisit:
+          type: string
+          format: date

modules/openapi-generator/src/test/resources/3_0/protobuf-schema/animal.proto

@@ -0,0 +1,31 @@
+/*
+  OAI Specification example for Polymorphism
+
+  No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)
+
+  The version of the OpenAPI document: 1.0.0
+
+  Generated by OpenAPI Generator: https://openapi-generator.tech
+*/
+
+syntax = "proto3";
+
+package openapitools;
+
+import public "models/care_details.proto";
+
+message Animal {
+
+  string pet_type = 482112090;
+
+  string bark = 3016376;
+
+  string name = 3373707;
+
+  string fur_color = 478695002;
+
+  bool is_indoor = 183319801;
+
+  CareDetails care_details = 176721135;
+
+}

modules/openapi-generator/src/test/resources/3_0/protobuf-schema/pet.proto

@@ -12,12 +12,16 @@ syntax = "proto3";
 
 package openapitools;
 
+import public "models/characteristics.proto";
+
 message Pet {
 
   string pet_type = 482112090;
 
   string name = 3373707;
 
+  Characteristics characteristics = 455429578;
+
   string bark = 3016376;
 
   bool loves_rocks = 465093427;