From ce3340621f7d72d4c65a1246aa63fed44c36ea54 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Mon, 26 Aug 2019 12:17:53 +0100
Subject: [PATCH] lib/readers: add NoCloser to stop upgrades from io.Reader to
 io.ReadCloser

---
 lib/readers/noclose.go      | 29 ++++++++++++++++++++++++
 lib/readers/noclose_test.go | 44 +++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 lib/readers/noclose.go
 create mode 100644 lib/readers/noclose_test.go

diff --git a/lib/readers/noclose.go b/lib/readers/noclose.go
new file mode 100644
index 000000000..dc36e8be2
--- /dev/null
+++ b/lib/readers/noclose.go
@@ -0,0 +1,29 @@
+package readers
+
+import "io"
+
+// noClose is used to wrap an io.Reader to stop it being upgraded
+type noClose struct {
+	in io.Reader
+}
+
+// Read implements io.Closer by passing it straight on
+func (nc noClose) Read(p []byte) (n int, err error) {
+	return nc.in.Read(p)
+}
+
+// NoCloser makes sure that the io.Reader passed in can't upgraded to
+// an io.Closer.
+//
+// This is for use with http.NewRequest to make sure the body doesn't
+// get upgraded to an io.Closer and the body closed unexpectedly.
+func NoCloser(in io.Reader) io.Reader {
+	if in == nil {
+		return in
+	}
+	// if in doesn't implement io.Closer, just return it
+	if _, canClose := in.(io.Closer); !canClose {
+		return in
+	}
+	return noClose{in: in}
+}
diff --git a/lib/readers/noclose_test.go b/lib/readers/noclose_test.go
new file mode 100644
index 000000000..da784425c
--- /dev/null
+++ b/lib/readers/noclose_test.go
@@ -0,0 +1,44 @@
+package readers
+
+import (
+	"io"
+	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/assert"
+)
+
+var errRead = errors.New("read error")
+
+type readOnly struct{}
+
+func (readOnly) Read(p []byte) (n int, err error) {
+	return 0, io.EOF
+}
+
+type readClose struct{}
+
+func (readClose) Read(p []byte) (n int, err error) {
+	return 0, errRead
+}
+
+func (readClose) Close() (err error) {
+	return io.EOF
+}
+
+func TestNoCloser(t *testing.T) {
+	assert.Equal(t, nil, NoCloser(nil))
+
+	ro := readOnly{}
+	assert.Equal(t, ro, NoCloser(ro))
+
+	rc := readClose{}
+	nc := NoCloser(rc)
+	assert.NotEqual(t, nc, rc)
+
+	_, hasClose := nc.(io.Closer)
+	assert.False(t, hasClose)
+
+	_, err := nc.Read(nil)
+	assert.Equal(t, errRead, err)
+}