r2.Request should follow 307 on non-GET

[dhermes]

See #175 for context. To test

package main

import (
	"fmt"
	"net/http"
	"net/http/httptest"
	"net/url"

	"github.com/blend/go-sdk/r2"
)

func main() {
	path := "/v1/auth/token/lookup"
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == path {
			http.Redirect(w, r, "/more", http.StatusTemporaryRedirect)
			return
		}
		fmt.Fprintln(w, "Hello, client")
	}))
	defer ts.Close()
	u, err := url.Parse(ts.URL)
	if err != nil {
		panic(err)
	}

	// Do a GET.
	fmt.Println("--- Doing a GET ---")
	opts := []r2.Option{
		r2.OptScheme("http"),
		r2.OptHeaderValue("X-Vault-Token", "bar"),
		r2.OptHost(u.Host),
		r2.OptGet(),
		r2.OptPathf(path),
	}
	body, res, err := r2.New("", opts...).Bytes()
	if err != nil {
		panic(err)
	}
	fmt.Printf("body: %q\n\n%#v\n", string(body), res)

	data := map[string]string{"token": "foo"}
	// Do a POST.
	fmt.Println("--- Doing a POST ---")
	opts = []r2.Option{
		r2.OptScheme("http"),
		r2.OptHeaderValue("X-Vault-Token", "bar"),
		r2.OptHost(u.Host),
		r2.OptPost(),
		r2.OptPathf(path),
		r2.OptJSONBody(data),
	}
	r := r2.New("", opts...)
	body, res, err = r.Bytes()
	if err != nil {
		panic(err)
	}
	fmt.Printf("body: %q\n\n%#v\n", string(body), res)
}

which produces

--- Doing a GET ---
body: "Hello, client\n"

&http.Response{Status:"200 OK", StatusCode:200, Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{"Content-Length":[]string{"14"}, "Content-Type":[]string{"text/plain; charset=utf-8"}, "Date":[]string{"Sat, 01 Feb 2020 00:01:16 GMT"}}, Body:(*http.bodyEOFSignal)(0xc0001bc100), ContentLength:14, TransferEncoding:[]string(nil), Close:false, Uncompressed:false, Trailer:http.Header(nil), Request:(*http.Request)(0xc0001c8000), TLS:(*tls.ConnectionState)(nil)}
--- Doing a POST ---
body: ""

&http.Response{Status:"307 Temporary Redirect", StatusCode:307, Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{"Content-Length":[]string{"0"}, "Date":[]string{"Sat, 01 Feb 2020 00:01:16 GMT"}, "Location":[]string{"/more"}}, Body:http.noBody{}, ContentLength:0, TransferEncoding:[]string(nil), Close:false, Uncompressed:false, Trailer:http.Header(nil), Request:(*http.Request)(0xc000176420), TLS:(*tls.ConnectionState)(nil)}

[dhermes]

OK, I tracked down what is caused this, it is the absence of r.Request.GetBody. This boils down to the same core issue as #154, #143, #141: We're trying to recreate what http.NewRequest() does by struct-embedding http.Request, but IMO we should not be struct embedding it because there are so many corner cases.

Applying the following updates to the script above

diff --git a/main.go b/main.go
index 8b95934..80a972e 100644
--- a/main.go
+++ b/main.go
@@ -1,7 +1,11 @@
 package main
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
+	"io"
+	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -40,6 +44,10 @@ func main() {
 	fmt.Printf("body: %q\n\n%#v\n", string(body), res)
 
 	data := map[string]string{"token": "foo"}
+	bodyBytes, err := json.Marshal(data)
+	if err != nil {
+		panic(err)
+	}
 	// Do a POST.
 	fmt.Println("--- Doing a POST ---")
 	opts = []r2.Option{
@@ -51,6 +59,9 @@ func main() {
 		r2.OptJSONBody(data),
 	}
 	r := r2.New("", opts...)
+	r.Request.GetBody = func() (io.ReadCloser, error) {
+		return ioutil.NopCloser(bytes.NewReader(bodyBytes)), nil
+	}
 	body, res, err = r.Bytes()
 	if err != nil {
 		panic(err)

we get

--- Doing a GET ---
body: "Hello, client\n"

&http.Response{Status:"200 OK", StatusCode:200, Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{"Content-Length":[]string{"14"}, "Content-Type":[]string{"text/plain; charset=utf-8"}, "Date":[]string{"Sat, 01 Feb 2020 06:09:57 GMT"}}, Body:(*http.bodyEOFSignal)(0xc0001da040), ContentLength:14, TransferEncoding:[]string(nil), Close:false, Uncompressed:false, Trailer:http.Header(nil), Request:(*http.Request)(0xc00019a200), TLS:(*tls.ConnectionState)(nil)}
--- Doing a POST ---
body: "Hello, client\n"

&http.Response{Status:"200 OK", StatusCode:200, Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{"Content-Length":[]string{"14"}, "Content-Type":[]string{"text/plain; charset=utf-8"}, "Date":[]string{"Sat, 01 Feb 2020 06:09:57 GMT"}}, Body:(*http.bodyEOFSignal)(0xc0000d8640), ContentLength:14, TransferEncoding:[]string(nil), Close:false, Uncompressed:false, Trailer:http.Header(nil), Request:(*http.Request)(0xc00019a300), TLS:(*tls.ConnectionState)(nil)}

[dhermes]

From the NewRequestWithContext in the standard library:

			req.GetBody = func() (io.ReadCloser, error) {
				r := bytes.NewReader(buf)
				return ioutil.NopCloser(r), nil
			}

[dhermes]

This was fixed by #178.