caddyhttp: Set http.error.message to the HandlerError message

[francislavoie]

Fix #4969

[mholt]

Thanks! Just to make sure I understand, does this mean that {http.error} is the generic error message if no custom message is set, and that {http.error.message} is always only the custom message?

[francislavoie]

For example:

:8883 {
    error "Custom Error Message" 503

    handle_errors {
        respond "
Message: {http.error.message}
Error: {http.error}
Status: {http.error.status_code}
Text: {http.error.status_text}
Trace: {http.error.trace}
"
    }
}

Will write out:

Message: Custom Error Message
Error: {id=1bdsihwsh} caddyhttp.StaticError.ServeHTTP (staticerror.go:110): HTTP 503: Custom Error Message
Status: 503
Text: Service Unavailable
Trace: caddyhttp.StaticError.ServeHTTP (staticerror.go:110)

[mholt]

Ah that's pretty good. LGTM! Thanks for the patch. Not sure how I forgot this... heh.

[francislavoie]

Yeah it's kinda wild, we've always documented it but it never worked 🤣

[bones-was-here]

Thanks for implementing this, but there seems to be a regression. When file_server generates a 404, Caddy simply terminates the connection without returning any status code or body. It doesn't log anything to stdout/stderr but I'm guessing it doesn't like handlerErr.Err.Error() being called when no message is set. It returns an error normally when the message is set by the error directive.

[francislavoie]

Please provide your full config and a reproduce case. I don't want to make assumptions like we had to do in the previous thread.

I find it very unlikely that this PR would have caused any kind of regression. It only sets a variable, that's it.

[francislavoie]

Alright yep I see it. handlerErr.Err is nil in that case. Whoops.

Making a followup PR.