fix(streams): tighten stream typings and guard optional runtime paths for duplex and wrapper utilities

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartstream',
-  version: '3.4.1',
+  version: '3.4.2',
   description: 'A library to simplify the creation and manipulation of Node.js streams, providing utilities for handling transform, duplex, and readable/writable streams effectively in TypeScript.'
 }

ts/smartstream.classes.smartduplex.ts

@@ -7,11 +7,11 @@ export interface IStreamTools {
 }
 
 export interface IStreamWriteFunction<T, rT> {
-  (chunkArg: T, toolsArg: IStreamTools): Promise<rT>;
+  (chunkArg: T, toolsArg: IStreamTools): Promise<rT | void | null | undefined>;
 }
 
 export interface IStreamFinalFunction<rT> {
-  (toolsArg: IStreamTools): Promise<rT>;
+  (toolsArg: IStreamTools): Promise<rT | void | null | undefined>;
 }
 
 export interface ISmartDuplexOptions<TInput, TOutput> extends DuplexOptions {
@@ -92,7 +92,7 @@ export class SmartDuplex<TInput = any, TOutput = any> extends Duplex {
   }
 
   // INSTANCE
-  private backpressuredArray: plugins.lik.BackpressuredArray<TOutput>;
+  private backpressuredArray: plugins.lik.BackpressuredArray<TOutput | null>;
   public options: ISmartDuplexOptions<TInput, TOutput>;
   private _consumerWantsData = false;
   private _readFunctionRunning = false;
@@ -114,7 +114,7 @@ export class SmartDuplex<TInput = any, TOutput = any> extends Duplex {
       )
     );
     this.options = safeOptions;
-    this.backpressuredArray = new plugins.lik.BackpressuredArray<TOutput>(
+    this.backpressuredArray = new plugins.lik.BackpressuredArray<TOutput | null>(
       this.options.highWaterMark || 1
     );
   }

ts/smartstream.classes.streamwrapper.ts

@@ -59,7 +59,7 @@ export class StreamWrapper {
     }
 
     // combine the stream
-    let finalStream = null;
+    let finalStream: plugins.stream.Duplex | null = null;
     let firstIteration: boolean = true;
     for (const stream of streamExecutionArray) {
       if (firstIteration === true) {
@@ -71,12 +71,17 @@ export class StreamWrapper {
       for (const customEventObject of this.customEventObjectArray) {
         stream.on(customEventObject.eventName, customEventObject.eventFunction);
       }
-      if (!firstIteration) {
+      if (!firstIteration && finalStream) {
         finalStream = finalStream.pipe(stream);
       }
       firstIteration = false;
     }
 
+    if (!finalStream) {
+      done.resolve();
+      return done.promise;
+    }
+
     this.streamStartedDeferred.resolve();
 
     let resolved = false;

ts/smartstream.functions.ts

@@ -1,4 +1,4 @@
-import { type TransformOptions } from 'stream';
+import { type DuplexOptions } from 'stream';
 import { SmartDuplex } from './smartstream.classes.smartduplex.js';
 
 export interface AsyncTransformFunction<TInput, TOutput> {
@@ -7,7 +7,7 @@ export interface AsyncTransformFunction<TInput, TOutput> {
 
 export function createTransformFunction<TInput, TOutput>(
   asyncFunction: AsyncTransformFunction<TInput, TOutput>,
-  options?: TransformOptions
+  options?: DuplexOptions
 ): SmartDuplex {
   const smartDuplexStream = new SmartDuplex({
     ...options,