Best way to debug a JSON response?

[asomers]

I'm trying to fetch some JSON data over http and then deserialize it into a structure, like this: response::json::<MyStruct>()?. But sometimes the JSON doesn't match my expectations, and the error simply says error decoding response body. That's not very helpful. How can I better debug this? Some ideas:

• dbg!(&response) doesn't work, because Response::fmt doesn't show the body.
• dbg!(response.text()) doesn't work, because Response::text consumes the Response object, so I can't both print the text and attempt to deserialize it into MyStruct.
• dbg!(response.clone().text()) doesn't work because Response doesn't implement Clone.

So far the best solution I've come up with involves actually fetching the data from the server twice. Is there a better way?

[seanmonstar]

response.json() is convenience for basically (you can check the source of the method on docs.rs):

let text = resp.text().await?;
serde_json::from_str(&text).map_err(crate::error::decode)

So, you could grab the text, and then match serde_json ..., and if it errors, print it out.

[asomers]

Thanks. That's exactly what I was looking for.

[asomers]

Actually, that doesn't work very well. The problem is that reqwest::error is a private module. Also, reqwest::Error::decode is a private function, and reqwest::error::Kind is a private type. There doesn't seem to be any public constructor for reqwest::Error, So I can't return a reqwest::Result after debugging the json.

[seanmonstar]

Oh, yea, you cannot do that. If you're debugging, you could just dump the text into a panic. from_str(blah).map_err(|e| panic!("json error ({e}), text: {text:?}")).