Protect from NPE when paths aren't provided

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

@@ -892,7 +892,7 @@ public List<File> generate() {
 
             sb.append(System.lineSeparator());
 
-            System.err.println(sb.toString());
+            LOGGER.error(sb.toString());
         } else {
             // This exists here rather than in the method which generates supporting files to avoid accidentally adding files after this metadata.
             if (generateSupportingFiles) {
@@ -924,6 +924,10 @@ protected File processTemplateToFile(Map<String, Object> templateData, String te
 
     public Map<String, List<CodegenOperation>> processPaths(Paths paths) {
         Map<String, List<CodegenOperation>> ops = new TreeMap<>();
+        // when input file is not valid and doesn't contain any paths
+        if(paths == null) {
+            return ops;
+        }
         for (String resourcePath : paths.keySet()) {
             PathItem path = paths.get(resourcePath);
             processOperation(resourcePath, "get", path.getGet(), ops, path);

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

@@ -29,6 +29,7 @@
 import org.openapitools.codegen.MockDefaultGenerator.WrittenTemplateBasedFile;
 import org.openapitools.codegen.config.CodegenConfigurator;
 import org.openapitools.codegen.languages.AbstractJavaCodegen;
+import org.openapitools.codegen.languages.DartClientCodegen;
 import org.openapitools.codegen.languages.JavaClientCodegen;
 import org.testng.Assert;
 import org.testng.annotations.Test;
@@ -507,6 +508,34 @@ public void testAuthorizationScopeValues_Issue392() {
         assertEquals(postScopes.size(), 2, "POST scopes don't match. actual:" + postScopes);
     }
 
+    @Test
+    public void testAuthorizationScopeValues_Issue6733() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("java")
+                .setLibrary(JavaClientCodegen.RESTEASY)
+                .setValidateSpec(false)
+                .setInputSpec("src/test/resources/3_0/regression-6734.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_TESTS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_DOCS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
+        // tests if NPE will crash generation when path in yaml arent provided
+        generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
+        generator.setGenerateMetadata(false);
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        Assert.assertEquals(files.size(), 1);
+        files.forEach(File::deleteOnExit);
+    }
+
     @Test
     public void testAuthorizationsHasMoreWhenFiltered() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/issue4584.yaml");
@@ -574,6 +603,7 @@ public void testImportMapping() throws IOException {
         importMappings.put("TypeAlias", "foo.bar.TypeAlias");
 
         File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
 
         final CodegenConfigurator configurator = new CodegenConfigurator()
                 .setGeneratorName("java")
@@ -594,6 +624,7 @@ public void testImportMapping() throws IOException {
         generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
         generator.setGenerateMetadata(false);
         List<File> files = generator.opts(clientOptInput).generate();
+        files.forEach(File::deleteOnExit);
 
         Assert.assertEquals(files.size(), 1);
         TestUtils.ensureContainsFile(files, output, "src/main/java/org/openapitools/client/model/ParentType.java");

modules/openapi-generator/src/test/resources/3_0/regression-6734.yaml

@@ -0,0 +1,21 @@
+openapi: 3.0.0
+info:
+  version: 1.0.0
+  title: Whatever this is
+  description: whatever this description is
+
+servers:
+  - url: http://127.0.0.1:8080/{basePath}
+    variables:
+      basePath:
+        default: v1
+
+components:
+  schemas:
+    MyModel:
+      type: object
+      description: Description of a model
+      properties:
+        sortOrder:
+          type: string
+          enum: [asc, desc]