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.go

@@ -353,17 +353,22 @@ func init() {
 - command - a string with the command name
 - arg - a list of arguments for the backend command
 - opt - a map of string to string of options
+- returnType - one of ("COMBINED_OUTPUT", "STREAM", "STREAM_ONLY_STDOUT", "STREAM_ONLY_STDERR")
+    - defaults to "COMBINED_OUTPUT" if not set
+    - the STREAM returnTypes will write the output to the body of the HTTP message
+    - the COMBINED_OUTPUT will write the output to the "result" parameter
 
 Returns
 
 - result - result from the backend command
+    - only set when using returnType "COMBINED_OUTPUT"
 - error	 - set if rclone exits with an error code
-- returnType - one of ("COMBINED_OUTPUT", "STREAM", "STREAM_ONLY_STDOUT". "STREAM_ONLY_STDERR")
+- returnType - one of ("COMBINED_OUTPUT", "STREAM", "STREAM_ONLY_STDOUT", "STREAM_ONLY_STDERR")
 
 For example
 
     rclone rc core/command command=ls -a mydrive:/ -o max-depth=1
-	rclone rc core/command -a ls -a mydrive:/ -o max-depth=1
+    rclone rc core/command -a ls -a mydrive:/ -o max-depth=1
 
 Returns
 
@@ -386,7 +391,6 @@ OR
 
 // rcRunCommand runs an rclone command with the given args and flags
 func rcRunCommand(ctx context.Context, in Params) (out Params, err error) {
-
 	command, err := in.GetString("command")
 	if err != nil {
 		command = ""
@@ -409,7 +413,7 @@ func rcRunCommand(ctx context.Context, in Params) (out Params, err error) {
 		returnType = "COMBINED_OUTPUT"
 	}
 
-	var httpResponse *http.ResponseWriter
+	var httpResponse http.ResponseWriter
 	httpResponse, err = in.GetHTTPResponseWriter()
 	if err != nil {
 		return nil, errors.Errorf("response object is required\n" + err.Error())
@@ -460,12 +464,14 @@ func rcRunCommand(ctx context.Context, in Params) (out Params, err error) {
 			"error":  false,
 		}, nil
 	} else if returnType == "STREAM_ONLY_STDOUT" {
-		cmd.Stdout = *httpResponse
+		cmd.Stdout = httpResponse
 	} else if returnType == "STREAM_ONLY_STDERR" {
-		cmd.Stderr = *httpResponse
+		cmd.Stderr = httpResponse
 	} else if returnType == "STREAM" {
-		cmd.Stdout = *httpResponse
-		cmd.Stderr = *httpResponse
+		cmd.Stdout = httpResponse
+		cmd.Stderr = httpResponse
+	} else {
+		return nil, errors.Errorf("Unknown returnType %q", returnType)
 	}
 
 	err = cmd.Run()

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)
+	})
 }

fs/rc/params.go

@@ -112,15 +112,15 @@ func (p Params) GetHTTPRequest() (*http.Request, error) {
 //
 // If the parameter isn't found then error will be of type
 // ErrParamNotFound and the returned value will be nil.
-func (p Params) GetHTTPResponseWriter() (*http.ResponseWriter, error) {
+func (p Params) GetHTTPResponseWriter() (http.ResponseWriter, error) {
 	key := "_response"
 	value, err := p.Get(key)
 	if err != nil {
 		return nil, err
 	}
-	request, ok := value.(*http.ResponseWriter)
+	request, ok := value.(http.ResponseWriter)
 	if !ok {
-		return nil, ErrParamInvalid{errors.Errorf("expecting *http.ResponseWriter value for key %q (was %T)", key, value)}
+		return nil, ErrParamInvalid{errors.Errorf("expecting http.ResponseWriter value for key %q (was %T)", key, value)}
 	}
 	return request, nil
 }

fs/rc/params_test.go

@@ -2,6 +2,8 @@ package rc
 
 import (
 	"fmt"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 	"time"
 
@@ -346,3 +348,53 @@ func TestParamsGetStructMissingOK(t *testing.T) {
 	assert.Equal(t, 4.2, out.Float)
 	assert.Equal(t, true, IsErrParamInvalid(e3), e3.Error())
 }
+
+func TestParamsGetHTTPRequest(t *testing.T) {
+	in := Params{}
+	req, err := in.GetHTTPRequest()
+	assert.Nil(t, req)
+	assert.Error(t, err)
+	assert.Equal(t, true, IsErrParamNotFound(err), err.Error())
+
+	in = Params{
+		"_request": 42,
+	}
+	req, err = in.GetHTTPRequest()
+	assert.Nil(t, req)
+	assert.Error(t, err)
+	assert.Equal(t, true, IsErrParamInvalid(err), err.Error())
+
+	r := new(http.Request)
+	in = Params{
+		"_request": r,
+	}
+	req, err = in.GetHTTPRequest()
+	assert.NotNil(t, req)
+	assert.NoError(t, err)
+	assert.Equal(t, r, req)
+}
+
+func TestParamsGetHTTPResponseWriter(t *testing.T) {
+	in := Params{}
+	wr, err := in.GetHTTPResponseWriter()
+	assert.Nil(t, wr)
+	assert.Error(t, err)
+	assert.Equal(t, true, IsErrParamNotFound(err), err.Error())
+
+	in = Params{
+		"_response": 42,
+	}
+	wr, err = in.GetHTTPResponseWriter()
+	assert.Nil(t, wr)
+	assert.Error(t, err)
+	assert.Equal(t, true, IsErrParamInvalid(err), err.Error())
+
+	var w http.ResponseWriter = httptest.NewRecorder()
+	in = Params{
+		"_response": w,
+	}
+	wr, err = in.GetHTTPResponseWriter()
+	assert.NotNil(t, wr)
+	assert.NoError(t, err)
+	assert.Equal(t, w, wr)
+}