Handling tunnel errors as network failure

packages/loot-core/src/server/post.ts

@@ -15,6 +15,21 @@ function throwIfNot200(res, text) {
       const json = JSON.parse(text);
       throw new PostError(json.reason);
     }
+
+    // Actual Sync Server may be exposed via a tunnel (e.g. ngrok). Tunnel errors should be treated as network errors.
+    const tunnelErrorHeaders = ['ngrok-error-code'];
+
+    const headerKeys = res.headers.keys().toArray();
+    const tunnelError = tunnelErrorHeaders.some(tunnelErrorHeader =>
+      headerKeys.includes(tunnelErrorHeader),
+    );
+
+    if (tunnelError) {
+      // Tunnel errors are present when the tunnel is active and the server is not reachable e.g. server is offline
+      // When we experience a tunnel error we treat it as a network failure
+      throw new PostError('network-failure');
+    }
+
     throw new PostError(text);
   }
 }

upcoming-release-notes/3697.md

@@ -0,0 +1,6 @@
+---
+category: Enhancements
+authors: [MikesGlitch]
+---
+
+Supporting the use of an ngrok tunnel when used to tunnel into actual-sync server