[typescript-fetch] Rework fix infinite recursion with self-referencing discriminator mappings (#22149)

* Prevent ConcurrentModificationException

* Update typescript-fetch samples

* Add fixture sample

* Update samples

Author: sermler

bin/configs/typescript-fetch-infinite-recursion-issue.yaml

@@ -0,0 +1,7 @@
+generatorName: typescript-fetch
+outputDir: samples/client/others/typescript-fetch/infinite-recursion-issue
+inputSpec: modules/openapi-generator/src/test/resources/3_0/typescript-fetch/infinite-recursion-issue.yaml
+templateDir: modules/openapi-generator/src/main/resources/typescript-fetch
+additionalProperties:
+  enumPropertyNaming: "original"
+  enumUnknownDefaultCase: true

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

@@ -1605,11 +1605,13 @@ public ExtendedCodegenModel(CodegenModel cm) {
             if (this.discriminator != null) {
                 Set<CodegenDiscriminator.MappedModel> mappedModels = this.discriminator.getMappedModels();
                 for(CodegenDiscriminator.MappedModel mappedModel : mappedModels) {
-                    if(mappedModel.getModelName().equals(cm.classname)){
-                        this.discriminator.getMappedModels().remove(mappedModel);
-                        this.selfReferencingDiscriminatorMapping=mappedModel;
+                    if(mappedModel.getModelName().equals(cm.classname)) {
+                        this.selfReferencingDiscriminatorMapping = mappedModel;
                     }
                 }
+                if(this.selfReferencingDiscriminatorMapping != null) {
+                    this.discriminator.getMappedModels().remove(this.selfReferencingDiscriminatorMapping);
+                }
             }
         }
 

modules/openapi-generator/src/test/resources/3_0/typescript-fetch/infinite-recursion-issue.yaml

@@ -0,0 +1,53 @@
+openapi: 3.0.3
+info:
+  title: Minimal
+  description: Api to reproduce bug
+  version: 0.5.1-SNAPSHOT.0
+tags:
+  - name: test
+servers:
+  - url: http://localhost:8080
+paths:
+  /api/v1/test:
+    get:
+      tags:
+        - test
+      operationId: test
+      responses:
+        "200":
+          description: test operation
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  $ref: "#/components/schemas/TestBaseDto"
+
+components:
+  schemas:
+    TestObjectType:
+      type: string
+      enum:
+        - TEST1
+        - TEST2
+    TestBaseDto:
+      type: object
+      properties:
+        something:
+          type: string
+        testObjectType:
+          $ref: "#/components/schemas/TestObjectType"
+      discriminator:
+        propertyName: testObjectType
+        mapping:
+          TEST2: '#/components/schemas/ExtendDto'
+          TEST1: '#/components/schemas/TestBaseDto'
+    ExtendDto:
+      allOf:
+        - $ref: '#/components/schemas/TestBaseDto'
+        - type: object
+          properties:
+            someItems:
+              type: array
+              items:
+                $ref: '#/components/schemas/TestBaseDto'