feat: noCollect option

README.md

@@ -29,15 +29,11 @@ const streamPromise = require("stream-promise");
 
 streamPromise(someReadableStream);
 
-someReadableStream.then(result => {
-	console.log("Concatenated stream output", result);
-});
+someReadableStream.then(result => { console.log("Concatenated stream output", result); });
 
 streamPromise(someWritabletream);
 
-someReadableStream.then(result => {
-	console.log("Cumulated stream output", result);
-});
+someReadableStream.then(result => { console.log("Cumulated stream output", result); });
 ```
 
 Already emitted data is accessible at `emittedData` property
@@ -51,11 +47,17 @@ const streamToPromise = require("stream-promise/to-promise");
 
 const someReadableStreamPromise = streamPromiseTo(someReadableStream);
 
-someReadableStreamPromise.then(result => {
-	console.log("Concatenated stream output", result);
-});
+someReadableStreamPromise.then(result => { console.log("Concatenated stream output", result); });
 ```
 
+## Supported options
+
+### noCollect `boolean` (default: `false`)
+
+Applicable to _readable_ streams. Set to true, if it's not intended to gather stream result and resolve with it.
+
+Then the only purpose of promise would be to indicate a moment when data stream is finalized
+
 ### Tests
 
 ```bash

to-promise.js

@@ -1,9 +1,11 @@
 "use strict";
 
-const toShortString = require("es5-ext/to-short-string-representation")
+const isObject      = require("es5-ext/object/is-object")
+    , toShortString = require("es5-ext/to-short-string-representation")
     , isStream      = require("is-stream");
 
-module.exports = stream => {
+module.exports = (stream, options = {}) => {
+	if (!isObject(options)) options = {};
 	if (!isStream(stream)) throw new TypeError(`${ toShortString(stream) } is not a stream`);
 	if (!isStream.readable(stream) && !isStream.writable(stream)) {
 		throw new TypeError(
@@ -15,7 +17,9 @@ module.exports = stream => {
 		stream.on("error", reject);
 
 		if (isStream.readable(stream)) {
-			if (stream._readableState.objectMode) {
+			if (options.noCollect) {
+				result = undefined;
+			} else if (stream._readableState.objectMode) {
 				result = [];
 				stream.on("data", data => result.push(data));
 			} else {
@@ -42,6 +46,6 @@ module.exports = stream => {
 			stream.on("finish", () => resolve());
 		}
 	});
-	if (isStream.readable) promise.emittedData = result;
+	if (isStream.readable && !options.noCollect) promise.emittedData = result;
 	return promise;
 };