From 53ec046d56f496f41eed5f37f8b1faffaea2b428 Mon Sep 17 00:00:00 2001
From: Borewit <Borewit@users.noreply.github.com>
Date: Fri, 2 Aug 2024 10:51:09 +0200
Subject: [PATCH] Run detection prior to TransformStream initialization
 (`start(controller)`).

---
 core.js | 53 ++++++++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/core.js b/core.js
index 2cc5af04..50809027 100644
--- a/core.js
+++ b/core.js
@@ -111,42 +111,37 @@ export class FileTypeParser {
 	async toDetectionStream(stream, options) {
 		const {sampleSize = reasonableDetectionSizeInBytes} = options;
 		let detectedFileType;
-		let firstChunk = null;
+		let firstChunk;
 
-		// Create a new ReadableStream to manage locking issues
-		const transformStream = new TransformStream({
-			async start(controller) {
-				const reader = stream.getReader({mode: 'byob'});
+		const reader = stream.getReader({mode: 'byob'});
+		try {
+			// Read the first chunk from the stream
+			const {value: chunk, done} = await reader.read(new Uint8Array(sampleSize));
+			firstChunk = chunk;
+			if (!done && chunk) {
 				try {
-					// Read the first chunk from the stream
-					const {value: chunk, done} = await reader.read(new Uint8Array(sampleSize));
-					firstChunk = chunk;
-					if (!done && chunk) {
-						try {
-							// Attempt to detect the file type from the chunk
-							detectedFileType = await this.fromBuffer(chunk.slice(0, sampleSize));
-						} catch (error) {
-							if (!(error instanceof strtok3.EndOfStreamError)) {
-								throw error; // Re-throw non-EndOfStreamError
-							}
-
-							detectedFileType = undefined;
-						}
+					// Attempt to detect the file type from the chunk
+					detectedFileType = await this.fromBuffer(chunk.slice(0, sampleSize));
+				} catch (error) {
+					if (!(error instanceof strtok3.EndOfStreamError)) {
+						throw error; // Re-throw non-EndOfStreamError
 					}
 
-					firstChunk = chunk;
-				} catch (error) {
-					controller.error(error); // Handle errors during start
-				} finally {
-					reader.releaseLock(); // Ensure the reader is released
+					detectedFileType = undefined;
 				}
+			}
+
+			firstChunk = chunk;
+		} finally {
+			reader.releaseLock(); // Ensure the reader is released
+		}
+
+		// Create a new ReadableStream to manage locking issues
+		const transformStream = new TransformStream({
+			async start(controller) {
+				controller.enqueue(firstChunk); // Enqueue the initial chunk
 			},
 			transform(chunk, controller) {
-				if (firstChunk) {
-					firstChunk = null;
-					controller.enqueue(firstChunk); // Enqueue the initial chunk
-				}
-
 				// Pass through the chunks without modification
 				controller.enqueue(chunk);
 			},