Wrong and weird behaviour of context in getServerSideProps with incorrect src on img

[alexbujenita]

What version of Next.js are you using?

11.1.2

What version of Node.js are you using?

14.17.6

What browser are you using?

Chrome

What operating system are you using?

macOS

How are you deploying your application?

local, both with dev and build-start

Describe the Bug

When using getServerSideProps with a param and then returning the data, if I'm rendering an with a wrong URL getServerSideProps gets called again but this time with the image URL as params!

GET http://localhost/person/1 Here here id is 1 GET http://localhost/person/3 Here is 3 and the again "image not found"

The ID 3 is with a wrong img src.

Expected Behavior

To not call getServerSideProps again with this weird behaviour

To Reproduce

pages/api/person/[id].js

export default function handler(req, res) {

  const data = [
    { id: 1, name: "John Doe", image: null },
    { id: 2, name: "Jane Doe", image: "https://upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Nextjs-logo.svg/1200px-Nextjs-logo.svg.png" },
    { id: 3, name: "Blah Doe", image: "image not found" },
  ];

  const person = data.find((p) => parseInt(req?.query?.id) === p.id)

  res.status(200).json(person);
}

pages/person/[id].js

export default function Person({ name, image }) {
  return (
    <div>
      <p>{name}</p>
      {image && <img alt="person" src={image} />}
    </div>
  );
}

export async function getServerSideProps(ctx) {
    console.log(ctx.params)
    const res = await fetch("http://localhost:3000/api/person/" + ctx.params.id);
    const data = await res.json();
    return {
      props: data,
  }

/person/1 and /2 will cause no error, /3 is the one with the weird bug.

[balazsorban44]

A few things:

1. If you have access to the logic that runs in /api/person/[id].js to fetch the image, you should import that in getServerSideProps, instead of using a fetch call:

Note: You should not use fetch() to call an API route in getServerSideProps. Instead, directly import the logic used inside your API route. You may need to slightly refactor your code for this approach. Fetching from an external API is fine!

https://nextjs.org/docs/basic-features/data-fetching#getserversideprops-server-side-rendering

This will avoid an unnecessary trip to get some data.

2. If your API resolves to return undefined as JSON, you won't be able to pass it as props, and Next.js is supposed to throw this error message:

Error: Error serializing `foo` returned from `getServerSideProps` in "/foo".
Reason: `undefined` cannot be serialized as JSON. Please use `null` or omit this value.

You should return null as a fallback prop, if there was no match.

In any case, with the code you provided, I could not reproduce the issue. The page renders "correctly"

[alexbujenita]

@balazsorban44 That's just a small reproduction, I don't care about wrong data being returned.

It's mostly to show a weird behaviour, getServerSideProps getting called with a param taken from somewhere else, in this case the url from the image, but why?!

EDIT: yes the page does render, but take a look at the console, you'll have another weird call to the backend this time though instead of having the ID (like 3 in this case), you'll see one call with the ID and one with the URL of the image!

That's the bug that I'm reporting

EDIT_2: sorry, just realized now about your comment about not calling the next API from there, this is just an example, I had this issue where I was calling a different external API.

[github-actions[bot]]

Please verify that your issue can be recreated with next@canary.

Why was this issue marked with the please verify canary label?

We noticed the provided reproduction was using an older version of Next.js, instead of canary.

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[balazsorban44]

This issue has been automatically closed because it wasn't verified against next@canary. If you think it was closed by accident, please leave a comment. If you are running into a similar issue, please open a new issue with a reproduction. Thank you.

[github-actions[bot]]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.