Fix: Inline models can't be generated (#1768)

* Add a test case

* Fix that the inline models couldn't be flatten when "components" doesn't exist

* Rename yaml file

* Rename method name

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

@@ -17,6 +17,7 @@
 
 package org.openapitools.codegen;
 
+import io.swagger.v3.oas.models.Components;
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.media.ArraySchema;
@@ -49,7 +50,7 @@ public class InlineModelResolver {
         this.openapi = openapi;
 
         if (openapi.getComponents() == null) {
-            return; // There's nothing here
+            openapi.setComponents(new Components());
         }
 
         if (openapi.getComponents().getSchemas() == null) {

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

@@ -24,7 +24,9 @@ import io.swagger.v3.oas.models.parameters.RequestBody;
 import io.swagger.v3.oas.models.responses.ApiResponse;
 import io.swagger.v3.oas.models.responses.ApiResponses;
 import io.swagger.v3.parser.core.models.ParseOptions;
+import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.utils.ModelUtils;
+import org.testng.Assert;
 import org.testng.annotations.Test;
 
 import java.util.HashMap;
@@ -274,6 +276,16 @@ public class InlineModelResolverTest {
         assertTrue(model.getProperties().get("name") instanceof StringSchema);
     }
 
+    @Test
+    public void resolveInlineRequestBodyWhenNoComponents() {
+        OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/inline_request_body_no_components.yaml", null, new ParseOptions()).getOpenAPI();
+        new InlineModelResolver().flatten(openAPI);
+
+        assertNotNull(openAPI.getComponents());
+        assertNotNull(openAPI.getComponents().getRequestBodies());
+    }
+    
+    /*
     @Test
     public void resolveInlineArraySchemaWithTitle() {
         OpenAPI openAPI = new OpenAPIParser().readLocation("src/test/resources/3_0/inline_model_resolver.yaml", null, new ParseOptions()).getOpenAPI();

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

@@ -0,0 +1,24 @@
+openapi: 3.0.1
+info:
+  version: 1.0.0
+  title: Example
+  license:
+    name: MIT
+servers:
+  - url: http://api.example.xyz/v1
+paths:
+  /test1:
+    post:
+      requestBody:
+        description: test
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                name:
+                  type: string
+      operationId: test1
+      responses:
+        '200':
+          description: OK