runtime.MarshalerForRequest: Content-Type should have been parsed before querying mimeMap

[movsb]

🐛 Bug Report

The Content-Type header field of http.Request may have parameters (MDN):

Content-Type: text/html; charset=UTF-8
Content-Type: multipart/form-data; boundary=something

But when we register a mime into mimeMap, we don't care them:

var m your.MsgPackMarshaler
mux := runtime.NewServeMux(
    runtime.WithMarshalerOption("application/x-msgpack", m),
)

A Content-Type with parameters causes no match:

grpc-gateway/runtime/marshaler_registry.go

Lines 33 to 38 in 855204b

	for _, contentTypeVal := range r.Header[contentTypeHeader] {
	if m, ok := mux.marshalers.mimeMap[contentTypeVal]; ok {
	inbound = m
	break
	}
	}

To Reproduce

Upload a file and we can see that Content-Type gets different parameters, every time:

$ curl -vF file=@go.mod localhost:2564/v3/ping 
*   Trying ::1...
* TCP_NODELAY set
* Connection failed
* connect to ::1 port 2564 failed: Connection refused
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 2564 (#0)
> POST /v3/ping HTTP/1.1
> Host: localhost:2564
> User-Agent: curl/7.64.1
> Accept: */*
> Content-Length: 1312
> Content-Type: multipart/form-data; boundary=------------------------574891a52a1a9324
> Expect: 100-continue
> 
< HTTP/1.1 100 Continue
* We are completely uploaded and fine
< HTTP/1.1 200 OK
< Content-Type: multipart/form-data
< Date: Mon, 06 Jul 2020 17:19:45 GMT
< Content-Length: 15
< 
* Connection #0 to host localhost left intact
{"pong":"pong"}* Closing connection 0

Expected behavior

Parse Content-Type before querying mimeMap:

diff --git a/runtime/marshaler_registry.go b/runtime/marshaler_registry.go
index 5cc53ae..17e63e4 100644
--- a/runtime/marshaler_registry.go
+++ b/runtime/marshaler_registry.go
@@ -2,6 +2,7 @@ package runtime
 
 import (
 	"errors"
+	"mime"
 	"net/http"
 )
 
@@ -31,7 +32,11 @@ func MarshalerForRequest(mux *ServeMux, r *http.Request) (inbound Marshaler, out
 	}
 
 	for _, contentTypeVal := range r.Header[contentTypeHeader] {
-		if m, ok := mux.marshalers.mimeMap[contentTypeVal]; ok {
+		contentType, _, err := mime.ParseMediaType(contentTypeVal)
+		if err != nil {
+			continue
+		}
+		if m, ok := mux.marshalers.mimeMap[contentType]; ok {
 			inbound = m
 			break
 		}

Actual Behavior

No marshaler was found.

Your Environment

Any.

[johanbrandhorst]

Hey, great find! Your fix looks pretty simple, would you care to create a pull request so we can get this fix in? Thanks!

[movsb]

Hi, @johanbrandhorst , pull request sent. Thanks. If test cases are required, I'll be willing to write one.