Enhancement: in REPL mode allow user to specify path to file for byte…

…s field

README.md

@@ -261,6 +261,11 @@ data (TYPE_BYTES) => \u65e5\u672c\u8a9e
 }
 ```
 
+Or specify the full path to a file using the `file://` prefix to the full path.
+```
+data (TYPE_BYTES) => file:///full/path/to/file.txt
+```
+
 ### Client streaming RPC
 Client streaming RPC accepts some requests and then returns only one response.  
 Finish request inputting with <kbd>CTRL-D</kbd>

fill/proto/convert.go

@@ -2,7 +2,9 @@ package proto
 
 import (
 	"fmt"
+	"io/ioutil"
 	"strconv"
+	"strings"
 
 	"github.com/golang/protobuf/protoc-gen-go/descriptor"
 	"github.com/pkg/errors"
@@ -80,6 +82,13 @@ func convertValue(pv string, fieldType descriptor.FieldDescriptorProto_Type) (in
 	// His expects "ogiso" in string, but backslashes in the input are not interpreted as an escape sequence.
 	// So, we need to call strconv.Unquote to interpret backslashes as an escape sequence.
 	case descriptor.FieldDescriptorProto_TYPE_BYTES:
+		const filePrefix = "file://"
+		if strings.HasPrefix(pv, filePrefix) {
+			pv = strings.TrimPrefix(pv, filePrefix)
+			v, err = ioutil.ReadFile(pv)
+			break
+		}
+
 		pv, err = strconv.Unquote(`"` + pv + `"`)
 		v = []byte(pv)
 

fill/proto/convert_test.go

@@ -80,6 +80,11 @@ func Test_convertValue(t *testing.T) {
 			fieldType: descriptor.FieldDescriptorProto_TYPE_BYTES,
 			expected:  []byte("小木曽"),
 		},
+		"bytes (read from file)": {
+			v:         "file://proto.go",
+			fieldType: descriptor.FieldDescriptorProto_TYPE_BYTES,
+			expected:  []byte("// Package proto provides a filler implementation for Protocol Buffers.\npackage proto\n"),
+		},
 		"bytes (Unicode literals)": {
 			v:         "\u5c0f\u6728\u66fd",
 			fieldType: descriptor.FieldDescriptorProto_TYPE_BYTES,