fix(Telegram Node): Determine the MIME type when downloading the file (#17725)

packages/nodes-base/nodes/Telegram/Telegram.node.ts

@@ -1,3 +1,4 @@
+import { lookup } from 'mime-types';
 import type {
 	IExecuteFunctions,
 	IDataObject,
@@ -656,6 +657,31 @@ export class Telegram implements INodeType {
 				default: true,
 				description: 'Whether to download the file',
 			},
+			{
+				displayName: 'Additional Fields',
+				name: 'additionalFields',
+				type: 'collection',
+				placeholder: 'Add Field',
+				displayOptions: {
+					show: {
+						operation: ['get'],
+						resource: ['file'],
+						download: [true],
+					},
+				},
+				default: {},
+				options: [
+					{
+						displayName: 'MIME Type',
+						name: 'mimeType',
+						type: 'string',
+						placeholder: 'image/jpeg',
+						default: '',
+						description:
+							'The MIME type of the file. If not specified, the MIME type will be determined by the file extension.',
+					},
+				],
+			},
 
 			// ----------------------------------
 			//         message
@@ -2169,11 +2195,15 @@ export class Telegram implements INodeType {
 							},
 						);
 
-						const fileName = filePath.split('/').pop();
+						const fileName = filePath.split('/').pop() as string;
+						const additionalFields = this.getNodeParameter('additionalFields', 0);
+						const providedMimeType = additionalFields?.mimeType as string | undefined;
+						const mimeType = providedMimeType ?? (lookup(fileName) || 'application/octet-stream');
 
 						const data = await this.helpers.prepareBinaryData(
 							file.body as Buffer,
-							fileName as string,
+							fileName,
+							mimeType,
 						);
 
 						returnData.push({