Error: SvelteKit server-side rendering encountered a TypeError when trying to fetch data. Unfortunately, Express is not providing a clear TypeScript stack trace

Question

Error: SvelteKit server-side rendering encountered a TypeError when trying to fetch data. Unfortunately, Express is not providing a clear TypeScript stack trace

I've been monitoring the logs of the SvelteKit SSR server using adapter-node.

After customizing the server.js to utilize Express instead of Polka, I noticed some errors occurring, particularly when the fetch() function attempts to retrieve data from the backend API and encounters failures.

The console output received while running on docker shows:

frontend  | TypeError: fetch failed
frontend  |     at fetch (file:///app/build/handler.js:17895:14)
frontend  |     at async Object.fetch (file:///app/build/server/index.js:2273:12)
frontend  |     at async fetch (file:///app/build/server/index.js:991:24)
frontend  |     at async Promise.all (index 0)
frontend  |     at async load (file:///app/build/server/chunks/6-0becfa88.js:8:56)
frontend  |     at async load_data (file:///app/build/server/index.js:1088:16)
frontend  |     at async file:///app/build/server/index.js:1887:18

This stack trace lacks details about which function or source code triggered the fetch() call. The abundance of functions named load() in a SvelteKit project further complicates pinpointing the issue.

To enhance error readability and SvelteKit's error handling overall, it would be beneficial to display more detailed information such as the specific caller mapped to its TypeScript source file, the name of the failed page, the URL causing failure in fetch(), and other pertinent details. This additional context could facilitate troubleshooting API call failures effectively.

javascript typescript express svelte sveltekit

Answer 1

Answer №1

The issue may be due to the absence of a sourcemap.

When SvelteKit compiles your application, it divides your code into multiple chunks, resulting in an unreadable error stack trace.

There is a solution to re-enable the sourcemap feature, which you can implement in your project to see if it resolves the problem.

Edit the vite.config.xx file and include the following configuration:

const config = {
  ...
  build:{
    sourcemap: true // Configure vite to generate sourcemap during bundling.
  },
  ...
}

Include the sourcemap flag when launching node, for instance:

node index.js --enable-source-maps

By following these steps, your stack trace should point to your src instead of build. Test this out to determine if your project still displays unclear stack traces.

Answer 2

The issue may be due to the absence of a sourcemap.

When SvelteKit compiles your application, it divides your code into multiple chunks, resulting in an unreadable error stack trace.

There is a solution to re-enable the sourcemap feature, which you can implement in your project to see if it resolves the problem.

Edit the vite.config.xx file and include the following configuration:

const config = {
  ...
  build:{
    sourcemap: true // Configure vite to generate sourcemap during bundling.
  },
  ...
}

Include the sourcemap flag when launching node, for instance:

node index.js --enable-source-maps

By following these steps, your stack trace should point to your src instead of build. Test this out to determine if your project still displays unclear stack traces.

Answer 3

Answer №2

To implement the handleFetch() function, you can create it within the file src/hooks.server.ts. In this function, make sure to log both the requested URL and page for reference:

// src/hooks.server.js

/** @type {import('@sveltejs/kit').HandleFetch} */
export function handleFetch({ event, request, fetch }) {

  let fetchResult;
  try {
      fetchResult = await fetch(request);
  } catch (error) {
      // Include logging of event and request details here.
  }

  return fetchResult;
}

Answer 4

To implement the handleFetch() function, you can create it within the file src/hooks.server.ts. In this function, make sure to log both the requested URL and page for reference:

// src/hooks.server.js

/** @type {import('@sveltejs/kit').HandleFetch} */
export function handleFetch({ event, request, fetch }) {

  let fetchResult;
  try {
      fetchResult = await fetch(request);
  } catch (error) {
      // Include logging of event and request details here.
  }

  return fetchResult;
}

Answer 5

Answer №3

Make sure to check the environment variable of your server. It's possible that you set NODE_ENV = 'production' on the server, but it is actually expecting 'development' instead. This mismatch could result in the URL being http://localhost, leading to a fetch error.

Answer 6

Make sure to check the environment variable of your server. It's possible that you set NODE_ENV = 'production' on the server, but it is actually expecting 'development' instead. This mismatch could result in the URL being http://localhost, leading to a fetch error.

Error: SvelteKit server-side rendering encountered a TypeError when trying to fetch data. Unfortunately, Express is not providing a clear TypeScript stack trace

Answer №1

Answer №2

Answer №3

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