Guess the scheme if r.URL.Scheme is unset

It's not expected that the request's URL is fully populated when used on
the server-side (it's more of a client-side field), so we shouldn't
expect it to be present.

In practice, it's only rarely set at all on the server, making mux's
`Schemes` matcher tricky to use as it is.

This commit adds a test which would have failed before demonstrating the
problem, as well as a fix which I think makes `.Schemes` match what
users expect.

mux_httpserver_test.go

@@ -0,0 +1,46 @@
+// +build go1.9
+
+package mux
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestSchemeMatchers(t *testing.T) {
+	router := NewRouter()
+	router.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
+		rw.Write([]byte("hello world"))
+	}).Schemes("http", "https")
+
+	assertHelloWorldResponse := func(t *testing.T, s *httptest.Server) {
+		resp, err := s.Client().Get(s.URL)
+		if err != nil {
+			t.Fatalf("unexpected error getting from server: %v", err)
+		}
+		if resp.StatusCode != 200 {
+			t.Fatalf("expected a status code of 200, got %v", resp.StatusCode)
+		}
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			t.Fatalf("unexpected error reading body: %v", err)
+		}
+		if !bytes.Equal(body, []byte("hello world")) {
+			t.Fatalf("response should be hello world, was: %q", string(body))
+		}
+	}
+
+	t.Run("httpServer", func(t *testing.T) {
+		s := httptest.NewServer(router)
+		defer s.Close()
+		assertHelloWorldResponse(t, s)
+	})
+	t.Run("httpsServer", func(t *testing.T) {
+		s := httptest.NewTLSServer(router)
+		defer s.Close()
+		assertHelloWorldResponse(t, s)
+	})
+}

mux_test.go

@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"net/http/httptest"
 	"net/url"
 	"reflect"
 	"strings"
@@ -2837,10 +2838,7 @@ func newRequestWithHeaders(method, url string, headers ...string) *http.Request
 
 // newRequestHost a new request with a method, url, and host header
 func newRequestHost(method, url, host string) *http.Request {
-	req, err := http.NewRequest(method, url, nil)
-	if err != nil {
-		panic(err)
-	}
+	req := httptest.NewRequest(method, url, nil)
 	req.Host = host
 	return req
 }

route.go

@@ -412,7 +412,20 @@ func (r *Route) Queries(pairs ...string) *Route {
 type schemeMatcher []string
 
 func (m schemeMatcher) Match(r *http.Request, match *RouteMatch) bool {
-	return matchInArray(m, r.URL.Scheme)
+	scheme := r.URL.Scheme
+	// https://golang.org/pkg/net/http/#Request
+	// "For [most] server requests, fields other than Path and RawQuery will be
+	// empty."
+	// Since we're an http muxer, the scheme is either going to be http or https
+	// though, so we can just set it based on the tls termination state.
+	if scheme == "" {
+		if r.TLS == nil {
+			scheme = "http"
+		} else {
+			scheme = "https"
+		}
+	}
+	return matchInArray(m, scheme)
 }
 
 // Schemes adds a matcher for URL schemes.