Mobile: Fixes #10396: Fix Dropbox sync (#10400)

packages/lib/file-api-driver-dropbox.js

@@ -130,16 +130,42 @@ class FileApiDriverDropbox {
 			// support POST requests with an empty body:
 			//
 			// https://www.dropboxforum.com/t5/Dropbox-API-Support-Feedback/Error-1017-quot-cannot-parse-response-quot/td-p/589595
+			const needsFetchWorkaround = shim.mobilePlatform() === 'ios';
+
+			const fetchPath = (method, path) => {
+				return this.api().exec(
+					method,
+					'files/download',
+					null,
+					{ 'Dropbox-API-Arg': JSON.stringify({ path: this.makePath_(path) }) },
+					options,
+				);
+			};
+
+			let response;
+			if (!needsFetchWorkaround) {
+				response = await fetchPath('POST', path);
+			} else {
+				try {
+					response = await fetchPath('GET', path);
+				} catch (_error) {
+					// May 2024: Sending a GET request to files/download sometimes fails
+					// until another file is requested. Because POST requests with empty bodies don't work on iOS,
+					// we send a request for a different file, then re-request the original.
+					//
+					// See https://github.com/laurent22/joplin/issues/10396
+
+					// This workaround requires that the file we request exist.
+					const { items } = await this.list();
+					const files = items.filter(item => !item.isDir && item.path !== path);
+
+					if (files.length > 0) {
+						await fetchPath('GET', files[0].path);
+					}
 
-			const response = await this.api().exec(
-				'GET',
-				'files/download',
-				null,
-				{
-					'Dropbox-API-Arg': JSON.stringify({ path: this.makePath_(path) }),
-				},
-				options,
-			);
+					response = await fetchPath('GET', path);
+				}
+			}
 			return response;
 		} catch (error) {
 			if (this.hasErrorCode_(error, 'not_found')) {