rc: fix core/command giving 500 internal error - fixes #4914

Before this change calling core/command gave the error

    error: response object is required expecting *http.ResponseWriter value for key "_response" (was *http.response)

This was because the http.ResponseWriter is an interface not an object.

Removing the `*` fixes the problem.

This also indicates that this bit of code wasn't properly tested.

fs/rc/internal_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -22,6 +23,12 @@ func TestMain(m *testing.M) {
 		fmt.Printf("rclone %s\n", fs.Version)
 		os.Exit(0)
 	}
+	// Pretend to error if we have an unknown command
+	if os.Args[len(os.Args)-1] == "unknown_command" {
+		fmt.Printf("rclone %s\n", fs.Version)
+		fmt.Fprintf(os.Stderr, "Unknown command\n")
+		os.Exit(1)
+	}
 	os.Exit(m.Run())
 }
 
@@ -136,17 +143,56 @@ func TestCoreQuit(t *testing.T) {
 func TestCoreCommand(t *testing.T) {
 	call := Calls.Get("core/command")
 
-	var httpResponse http.ResponseWriter = httptest.NewRecorder()
+	test := func(command string, returnType string, wantOutput string, fail bool) {
+		var rec = httptest.NewRecorder()
+		var w http.ResponseWriter = rec
 
-	in := Params{
-		"command":   "version",
-		"opt":       map[string]string{},
-		"arg":       []string{},
-		"_response": &httpResponse,
+		in := Params{
+			"command":   command,
+			"opt":       map[string]string{},
+			"arg":       []string{},
+			"_response": w,
+		}
+		if returnType != "" {
+			in["returnType"] = returnType
+		} else {
+			returnType = "COMBINED_OUTPUT"
+		}
+		stream := strings.HasPrefix(returnType, "STREAM")
+		got, err := call.Fn(context.Background(), in)
+		if stream && fail {
+			assert.Error(t, err)
+		} else {
+			assert.NoError(t, err)
+		}
+
+		if !stream {
+			assert.Equal(t, wantOutput, got["result"])
+			assert.Equal(t, fail, got["error"])
+		} else {
+			assert.Equal(t, wantOutput, rec.Body.String())
+		}
+		assert.Equal(t, http.StatusOK, rec.Result().StatusCode)
 	}
-	got, err := call.Fn(context.Background(), in)
-	require.NoError(t, err)
 
-	assert.Equal(t, fmt.Sprintf("rclone %s\n", fs.Version), got["result"])
-	assert.Equal(t, false, got["error"])
+	version := fmt.Sprintf("rclone %s\n", fs.Version)
+	errorString := "Unknown command\n"
+	t.Run("OK", func(t *testing.T) {
+		test("version", "", version, false)
+	})
+	t.Run("Fail", func(t *testing.T) {
+		test("unknown_command", "", version+errorString, true)
+	})
+	t.Run("Combined", func(t *testing.T) {
+		test("unknown_command", "COMBINED_OUTPUT", version+errorString, true)
+	})
+	t.Run("Stderr", func(t *testing.T) {
+		test("unknown_command", "STREAM_ONLY_STDERR", errorString, true)
+	})
+	t.Run("Stdout", func(t *testing.T) {
+		test("unknown_command", "STREAM_ONLY_STDOUT", version, true)
+	})
+	t.Run("Stream", func(t *testing.T) {
+		test("unknown_command", "STREAM", version+errorString, true)
+	})
 }