Fixing handler input type for Union

CHANGELOG.md

@@ -32,6 +32,7 @@ const endpoint = factory.build({
   })
 });
 ```
+- Supplying parameters to `EndpointsFactory::constructor()` is now prohibited. Please use `.addMiddleware()` and `.setResultHandler()` as the right way in order to achieve the correct input schema type in handlers.
 
 ### v0.6.1
 - Nothing special. Just new logo and the dataflow diagram update.

package.json

@@ -41,6 +41,7 @@
     "node-fetch": "^2.6.1",
     "ts-jest": "^26.5.1",
     "ts-node": "^9.1.1",
+    "tsd": "^0.15.1",
     "typescript": "^4.1.5"
   },
   "repository": {

src/endpoints-factory.ts

@@ -7,25 +7,27 @@ import {ResultHandler} from './result-handler';
 /** mIN, mOUT - accumulated from all middlewares */
 export class EndpointsFactory<mIN, mOUT> {
   protected middlewares: MiddlewareDefinition<any, any, any>[] = [];
-  protected resultHandler: ResultHandler | null;
+  protected resultHandler: ResultHandler | null = null;
 
-  constructor(
-    middlewares: MiddlewareDefinition<any, any, any>[] = [],
-    resultHandler: ResultHandler | null = null
+  private static create<mIN, mOUT>(
+    middlewares: MiddlewareDefinition<any, any, any>[],
+    resultHandler: ResultHandler | null
   ) {
-    this.middlewares = middlewares;
-    this.resultHandler = resultHandler;
+    const factory = new EndpointsFactory<mIN, mOUT>();
+    factory.middlewares = middlewares;
+    factory.resultHandler = resultHandler;
+    return factory;
   }
 
   public setResultHandler(resultHandler: ResultHandler) {
-    return new EndpointsFactory<mIN, mOUT>(
+    return EndpointsFactory.create<mIN, mOUT>(
       this.middlewares,
       resultHandler
     );
   }
 
   public addMiddleware<IN extends IOSchema, OUT extends FlatObject>(definition: MiddlewareDefinition<IN, mOUT, OUT>) {
-    return new EndpointsFactory<Merge<IN, mIN>, mOUT & OUT>(
+    return EndpointsFactory.create<Merge<IN, mIN>, mOUT & OUT>(
       this.middlewares.concat(definition),
       this.resultHandler
     );

src/helpers.ts

@@ -4,30 +4,32 @@ import {LoggerConfig, loggerLevels} from './config-type';
 import {MiddlewareDefinition} from './middleware';
 
 export type FlatObject = Record<string, any>;
-type EmptyFlatObject = {[K in never]: never};
+// type EmptyFlatObject = {[K in never]: never};
 
 type ObjectSchema = z.AnyZodObject;
-type Extractable = 'shape' | '_unknownKeys' | '_catchall';
+type Extractable = 'shape' | '_unknownKeys' | '_catchall' | '_output' | '_input';
 type UnionSchema = z.ZodUnion<[ObjectSchema, ...ObjectSchema[]]>;
 type IntersectionSchema = z.ZodIntersection<ObjectSchema, ObjectSchema>;
 
 export type IOSchema = ObjectSchema | UnionSchema | IntersectionSchema;
 
 type ArrayElement<T extends readonly unknown[]> = T extends readonly (infer K)[] ? K : never;
 
-type UnionResult<T extends ObjectSchema[], F extends Extractable> = Partial<ArrayElement<T>[F]>;
+type UnionResult<T extends ObjectSchema[], F extends Extractable> = ArrayElement<T>[F];
 type IntersectionResult<T extends IntersectionSchema, F extends Extractable> =
   T['_def']['left'][F] & T['_def']['right'][F];
 
 type IOExtract<T extends IOSchema | any, F extends Extractable> =
   T extends ObjectSchema ? T[F] :
   T extends UnionSchema ? UnionResult<T['options'], F> :
-  T extends IntersectionSchema ? IntersectionResult<T, F> : EmptyFlatObject;
+  T extends IntersectionSchema ? IntersectionResult<T, F> : unknown; // : EmptyFlatObject
 
 export type Merge<A extends IOSchema, B extends IOSchema | any> = z.ZodObject<
   IOExtract<A, 'shape'> & IOExtract<B, 'shape'>,
   IOExtract<A, '_unknownKeys'>,
-  IOExtract<A, '_catchall'>
+  IOExtract<A, '_catchall'>,
+  IOExtract<A, '_output'> & IOExtract<B, '_output'>,
+  IOExtract<A, '_input'> & IOExtract<B, '_input'>
 >;
 
 export function extractObjectSchema(subject: IOSchema): ObjectSchema {