caddyhttp: ensure ResponseWriterWrapper and ResponseRecorder use ReadFrom if the underlying response writer implements it. (#5022)

Doing so allows for splice/sendfile optimizations when available.
Fixes #4731

Co-authored-by: flga <flga@users.noreply.github.com>
Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>

1 files changed, 165 insertions, 0 deletions

diff --git a/modules/caddyhttp/responsewriter_test.go b/modules/caddyhttp/responsewriter_test.go
new file mode 100644
index 0000000..1913932
--- /dev/null
+++ b/modules/caddyhttp/responsewriter_test.go
@@ -0,0 +1,165 @@
+package caddyhttp
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+type responseWriterSpy interface {
+	http.ResponseWriter
+	Written() string
+	CalledReadFrom() bool
+}
+
+var (
+	_ responseWriterSpy = (*baseRespWriter)(nil)
+	_ responseWriterSpy = (*readFromRespWriter)(nil)
+)
+
+// a barebones http.ResponseWriter mock
+type baseRespWriter []byte
+
+func (brw *baseRespWriter) Write(d []byte) (int, error) {
+	*brw = append(*brw, d...)
+	return len(d), nil
+}
+func (brw *baseRespWriter) Header() http.Header        { return nil }
+func (brw *baseRespWriter) WriteHeader(statusCode int) {}
+func (brw *baseRespWriter) Written() string            { return string(*brw) }
+func (brw *baseRespWriter) CalledReadFrom() bool       { return false }
+
+// an http.ResponseWriter mock that supports ReadFrom
+type readFromRespWriter struct {
+	baseRespWriter
+	called bool
+}
+
+func (rf *readFromRespWriter) ReadFrom(r io.Reader) (int64, error) {
+	rf.called = true
+	return io.Copy(&rf.baseRespWriter, r)
+}
+
+func (rf *readFromRespWriter) CalledReadFrom() bool { return rf.called }
+
+func TestResponseWriterWrapperReadFrom(t *testing.T) {
+	tests := map[string]struct {
+		responseWriter responseWriterSpy
+		wantReadFrom   bool
+	}{
+		"no ReadFrom": {
+			responseWriter: &baseRespWriter{},
+			wantReadFrom:   false,
+		},
+		"has ReadFrom": {
+			responseWriter: &readFromRespWriter{},
+			wantReadFrom:   true,
+		},
+	}
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			// what we expect middlewares to do:
+			type myWrapper struct {
+				*ResponseWriterWrapper
+			}
+
+			wrapped := myWrapper{
+				ResponseWriterWrapper: &ResponseWriterWrapper{ResponseWriter: tt.responseWriter},
+			}
+
+			const srcData = "boo!"
+			// hides everything but Read, since strings.Reader implements WriteTo it would
+			// take precedence over our ReadFrom.
+			src := struct{ io.Reader }{strings.NewReader(srcData)}
+
+			fmt.Println(name)
+			if _, err := io.Copy(wrapped, src); err != nil {
+				t.Errorf("Copy() err = %v", err)
+			}
+
+			if got := tt.responseWriter.Written(); got != srcData {
+				t.Errorf("data = %q, want %q", got, srcData)
+			}
+
+			if tt.responseWriter.CalledReadFrom() != tt.wantReadFrom {
+				if tt.wantReadFrom {
+					t.Errorf("ReadFrom() should have been called")
+				} else {
+					t.Errorf("ReadFrom() should not have been called")
+				}
+			}
+		})
+	}
+}
+
+func TestResponseRecorderReadFrom(t *testing.T) {
+	tests := map[string]struct {
+		responseWriter responseWriterSpy
+		shouldBuffer   bool
+		wantReadFrom   bool
+	}{
+		"buffered plain": {
+			responseWriter: &baseRespWriter{},
+			shouldBuffer:   true,
+			wantReadFrom:   false,
+		},
+		"streamed plain": {
+			responseWriter: &baseRespWriter{},
+			shouldBuffer:   false,
+			wantReadFrom:   false,
+		},
+		"buffered ReadFrom": {
+			responseWriter: &readFromRespWriter{},
+			shouldBuffer:   true,
+			wantReadFrom:   false,
+		},
+		"streamed ReadFrom": {
+			responseWriter: &readFromRespWriter{},
+			shouldBuffer:   false,
+			wantReadFrom:   true,
+		},
+	}
+	for name, tt := range tests {
+		t.Run(name, func(t *testing.T) {
+			var buf bytes.Buffer
+
+			rr := NewResponseRecorder(tt.responseWriter, &buf, func(status int, header http.Header) bool {
+				return tt.shouldBuffer
+			})
+
+			const srcData = "boo!"
+			// hides everything but Read, since strings.Reader implements WriteTo it would
+			// take precedence over our ReadFrom.
+			src := struct{ io.Reader }{strings.NewReader(srcData)}
+
+			if _, err := io.Copy(rr, src); err != nil {
+				t.Errorf("Copy() err = %v", err)
+			}
+
+			wantStreamed := srcData
+			wantBuffered := ""
+			if tt.shouldBuffer {
+				wantStreamed = ""
+				wantBuffered = srcData
+			}
+
+			if got := tt.responseWriter.Written(); got != wantStreamed {
+				t.Errorf("streamed data = %q, want %q", got, wantStreamed)
+			}
+			if got := buf.String(); got != wantBuffered {
+				t.Errorf("buffered data = %q, want %q", got, wantBuffered)
+			}
+
+			if tt.responseWriter.CalledReadFrom() != tt.wantReadFrom {
+				if tt.wantReadFrom {
+					t.Errorf("ReadFrom() should have been called")
+				} else {
+					t.Errorf("ReadFrom() should not have been called")
+				}
+			}
+		})
+	}
+}