Types like http.Request and slog.LogValuer

[Jens-Uwe Mager]

I am trying to convert some older code to slog and I am running into the issue that if some data structure contains http.Request I get the message:

{"time":"2023-07-27T15:49:04.744214+02:00","level":"DEBUG","msg":"req","r":"!ERROR:json: unsupported type: func() (io.ReadCloser, error)"}

So I believed it would be a good idea to add a LogValue() function to http.Request that used httputil.DumpRequest(), but that does not work as I cannot add methods from my code. Any good idea to approach that?

[Jonathan Amsterdam]

I would write a type that wraps the request and implements LogValuer. Then you would log the request as

     logger.Debug("req", "r", requestWrapper{r})

[Jens-Uwe Mager]

There is a slight problem here that the requestWrapper would have to be implemented very deep through many layers of library. For example there might be a data structure passed down a chain of handlers with a custom argument structure, which contains a http.Request per some old design decisions. Switching to slog probably makes me revisit this design, as I cannot easily get the http.Request out of that structure easily. And this custom structure is logged all over the place.

Oh well.

[Jonathan Amsterdam]

Another idea: write a handler that wraps whatever handler you usually use. That handler looks through the Record for attr values of type *http.Request, and replaces them with whatever formatting you want.

You might even be able to do that with a ReplaceAttr function with the built-in handlers.

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