/cc @bradfitz @rsc @empijei @neild

This seems reasonable to me, especially given that this error is replacing a more-informative (to programs) tls.RecordHeaderError.

Perhaps the error returned here should wrap the tls.RecordHeaderError rather than replacing it.

Three concrete possibilities that I can think of:

1. Expose an ErrHTTPResponse var:

   ErrHTTPResponse = errors.New("http: server gave HTTP response to HTTPS client")

   [+] Simple.
   [-] Inconsistently returns ErrHTTPResponse or tls.RecordHeaderError depending on the response.

2. Don't expose a var, but make the error wrap the underlying tls.RecordHeaderError. In the case where someone wants to detect this condition, they can use errors.As to recover the underlying error and examine it:

   var tlsErr tls.RecordHeaderError
   if errors.As(err, &tlsErr) && string(tlsErr.RecordHeader[:]) == "HTTP/" {
       // ...
   }

   [+] Consistently return the underlying tls.RecordHeaderError.
   [-] Detecting the error condition is more work for the caller.
   [+] Contract with the caller is clear: We provide the tls.RecordHeaderError and they can decide how to interpret it.

3. Both: Return an error which errors.Is equivalent to an ErrHTTPResponse sentinel and which also wraps tls.RecordHeaderError.
   [-] Lot of mechanism for a fairly obscure case.

Option (2) requires the least change to the http API surface, but (1) is the simplest. Either of those seems reasonable to me.

Can we wrap (2) in a function like func IsNotHTTPS(err error) bool?

I'm fine with (2). Or (1) if we name it, say, ErrSchemeMismatch ("HTTP" in "ErrHTTPResponse" sounds too generic, as "HTTP" often also means "HTTPS").

I wouldn't want to see a new function. That's too heavy in godoc for how fringe this is.

Hi @bradfitz @rsc @empijei @neild any solution regarding this error message? @AkihiroSuda did you found the solution?
I tried to post and I got the same error message "http server gave http response to https client"

Thank you

PR: #50939 (ErrSchemeMismatch)

Change https://golang.org/cl/382117 mentions this issue: net/http: expose "http: server gave HTTP response to HTTPS client" error

@bradfitz Any chance to get the PR #50939 merged? 🙏

This is a proposed API change, so adding to the proposal process.

Specific proposal:

Add http.ErrSchemeMismatch, a distinguishable error that indicates an HTTPS server received what looks like an HTTP request. This converts an existing error to an exported, distinguishable symbol. See https://go.dev/cl/382117.

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

Sounds like everyone is in favor of this. Have all concerns been addressed?

Sounds like everyone is in favor of this. Have all concerns been addressed?

I don't see any remaining concern

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

Change https://go.dev/cl/496795 mentions this issue: doc: fill out net/http.ErrSchemeMismatch note