[typescript-fetch] fix serialization/deserialization with inheritance (#3767)

* #3646 - fix inheritence

* #3646: Fix imports

* Update modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache

Co-Authored-By: Esteban Gehring <esteban.gehring@gmail.com>

* generate typeescript-fetch samples

modules/openapi-generator/src/main/resources/typescript-fetch/modelEnum.mustache

@@ -12,6 +12,10 @@ export enum {{classname}} {
 }
 
 export function {{classname}}FromJSON(json: any): {{classname}} {
+    return {{classname}}FromJSONTyped(json, false);
+}
+
+export function {{classname}}FromJSONTyped(json: any, ignoreDiscriminator: boolean): {{classname}} {
     return json as {{classname}};
 }
 

modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache

@@ -4,11 +4,20 @@ import {
     {{#imports}}
     {{{.}}},
     {{.}}FromJSON,
+    {{.}}FromJSONTyped,
     {{.}}ToJSON,
     {{/imports}}
 } from './';
 
 {{/hasImports}}
+{{#discriminator}}
+import {
+{{#discriminator.mappedModels}}
+     {{modelName}}FromJSONTyped
+{{/discriminator.mappedModels}}
+} from './';
+
+{{/discriminator}}
 /**
  * {{{description}}}
  * @export
@@ -29,8 +38,25 @@ export interface {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{
 }
 
 export function {{classname}}FromJSON(json: any): {{classname}} {
+    return {{classname}}FromJSONTyped(json, false);
+}
+
+export function {{classname}}FromJSONTyped(json: any, ignoreDiscriminator: boolean): {{classname}} {
     {{#hasVars}}
+    if ((json === undefined) || (json === null)) {
+        return json;
+    }
+{{#discriminator}}
+    if (!ignoreDiscriminator) {
+{{#discriminator.mappedModels}}
+        if (json['{{discriminator.propertyName}}'] === '{{modelName}}') {
+            return {{modelName}}FromJSONTyped(json, true);
+        }
+{{/discriminator.mappedModels}}
+    }
+{{/discriminator}}
     return {
+        {{#parent}}...{{{parent}}}FromJSONTyped(json, ignoreDiscriminator),{{/parent}}
         {{#additionalPropertiesType}}
             ...json,
         {{/additionalPropertiesType}}
@@ -79,7 +105,11 @@ export function {{classname}}ToJSON(value?: {{classname}}): any {
     if (value === undefined) {
         return undefined;
     }
+    if (value === null) {
+        return null;
+    }
     return {
+        {{#parent}}...{{{parent}}}ToJSON(value),{{/parent}}
         {{#additionalPropertiesType}}
             ...value,
         {{/additionalPropertiesType}}