[MM-9937] Add support for sending a message to a different channel than where the slash command was issued from (#9878)

* add support for channel_id in a slash command response

* add test for HandleCommandResponsePost

app/command.go

@@ -41,6 +41,13 @@ func (a *App) CreateCommandPost(post *model.Post, teamId string, response *model
 	post.Message = model.ParseSlackLinksToMarkdown(response.Text)
 	post.CreateAt = model.GetMillis()
 
+	_, err := a.GetChannelMember(post.ChannelId, post.UserId)
+	if err != nil {
+		err = model.NewAppError("CreateCommandPost", "api.command.command_post.forbidden.app_error", nil, err.Error(), http.StatusForbidden)
+		mlog.Error(err.Error())
+		return nil, err
+	}
+
 	if strings.HasPrefix(post.Type, model.POST_SYSTEM_MESSAGE_PREFIX) {
 		err := model.NewAppError("CreateCommandPost", "api.context.invalid_param.app_error", map[string]interface{}{"Name": "post.type"}, "", http.StatusBadRequest)
 		return nil, err
@@ -301,7 +308,7 @@ func (a *App) HandleCommandResponse(command *model.Command, args *model.CommandA
 	return response, nil
 }
 
-func (a *App) HandleCommandResponsePost(command *model.Command, args *model.CommandArgs, response *model.CommandResponse, builtIn bool) (*model.CommandResponse, *model.AppError) {
+func (a *App) HandleCommandResponsePost(command *model.Command, args *model.CommandArgs, response *model.CommandResponse, builtIn bool) (*model.Post, *model.AppError) {
 	post := &model.Post{}
 	post.ChannelId = args.ChannelId
 	post.RootId = args.RootId
@@ -310,6 +317,10 @@ func (a *App) HandleCommandResponsePost(command *model.Command, args *model.Comm
 	post.Type = response.Type
 	post.Props = response.Props
 
+	if len(response.ChannelId) != 0 {
+		post.ChannelId = response.ChannelId
+	}
+
 	isBotPost := !builtIn
 
 	if a.Config().ServiceSettings.EnablePostUsernameOverride {
@@ -346,7 +357,7 @@ func (a *App) HandleCommandResponsePost(command *model.Command, args *model.Comm
 		mlog.Error(err.Error())
 	}
 
-	return response, nil
+	return post, nil
 }
 
 func (a *App) CreateCommand(cmd *model.Command) (*model.Command, *model.AppError) {

app/command_test.go

@@ -61,7 +61,142 @@ func TestCreateCommandPost(t *testing.T) {
 	}
 
 	_, err := th.App.CreateCommandPost(post, th.BasicTeam.Id, resp)
-	if err == nil && err.Id != "api.context.invalid_param.app_error" {
+	if err == nil || err.Id != "api.context.invalid_param.app_error" {
 		t.Fatal("should have failed - bad post type")
 	}
+
+	channel := th.CreateChannel(th.BasicTeam)
+
+	post = &model.Post{
+		ChannelId: th.BasicChannel.Id,
+		UserId:    channel.Id,
+	}
+
+	_, err = th.App.CreateCommandPost(post, th.BasicTeam.Id, resp)
+	if err == nil || err.Id != "api.command.command_post.forbidden.app_error" {
+		t.Fatal("should have failed - forbidden channel post")
+	}
+}
+
+func TestHandleCommandResponsePost(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	command := &model.Command{}
+	args := &model.CommandArgs{
+		ChannelId: th.BasicChannel.Id,
+		TeamId: th.BasicTeam.Id,
+		UserId: th.BasicUser.Id,
+		RootId: "root_id",
+		ParentId: "parent_id",
+	}
+
+	resp := &model.CommandResponse{
+		Type: model.POST_EPHEMERAL,
+		Props: model.StringInterface{"some_key": "some value"},
+		Text: "some message",
+	}
+
+	builtIn := true
+
+	post, err := th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, args.ChannelId, post.ChannelId)
+	assert.Equal(t, args.RootId, post.RootId)
+	assert.Equal(t, args.ParentId, post.ParentId)
+	assert.Equal(t, args.UserId, post.UserId)
+	assert.Equal(t, resp.Type, post.Type)
+	assert.Equal(t, resp.Props, post.Props)
+	assert.Equal(t, resp.Text, post.Message)
+	assert.Nil(t, post.Props["override_icon_url"])
+	assert.Nil(t, post.Props["override_username"])
+	assert.Nil(t, post.Props["from_webhook"])
+
+	// Command is not built in, so it is a bot command.
+	builtIn = false
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Equal(t, "true", post.Props["from_webhook"])
+
+	builtIn = true
+
+	// Channel id is specified by response, it should override the command args value.
+	channel := th.CreateChannel(th.BasicTeam)
+	resp.ChannelId = channel.Id
+	th.AddUserToChannel(th.BasicUser, channel)
+
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, resp.ChannelId, post.ChannelId)
+	assert.NotEqual(t, args.ChannelId, post.ChannelId)
+
+	// Override username config is turned off. No override should occur.
+	th.App.Config().ServiceSettings.EnablePostUsernameOverride = false
+	resp.ChannelId = ""
+	command.Username = "Command username"
+	resp.Username = "Response username"
+
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Nil(t, post.Props["override_username"])
+
+	th.App.Config().ServiceSettings.EnablePostUsernameOverride = true
+
+	// Override username config is turned on. Override username through command property.
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, command.Username, post.Props["override_username"])
+	assert.Equal(t, "true", post.Props["from_webhook"])
+
+	command.Username = ""
+
+	// Override username through response property.
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, resp.Username, post.Props["override_username"])
+	assert.Equal(t, "true", post.Props["from_webhook"])
+
+	th.App.Config().ServiceSettings.EnablePostUsernameOverride = false
+
+	// Override icon url config is turned off. No override should occur.
+	th.App.Config().ServiceSettings.EnablePostIconOverride = false
+	command.IconURL = "Command icon url"
+	resp.IconURL = "Response icon url"
+
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Nil(t, post.Props["override_icon_url"])
+
+	th.App.Config().ServiceSettings.EnablePostIconOverride = true
+
+	// Override icon url config is turned on. Override icon url through command property.
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, command.IconURL, post.Props["override_icon_url"])
+	assert.Equal(t, "true", post.Props["from_webhook"])
+
+	command.IconURL = ""
+
+	// Override icon url through response property.
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, resp.IconURL, post.Props["override_icon_url"])
+	assert.Equal(t, "true", post.Props["from_webhook"])
+
+	// Test Slack text conversion.
+	resp.Text = "<!channel>"
+
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, "@channel", post.Message)
+
+	// Test Slack attachments text conversion.
+	resp.Attachments = []*model.SlackAttachment{
+		&model.SlackAttachment{
+			Text: "<!here>",
+		},
+	}
+
+	post, err = th.App.HandleCommandResponsePost(command, args, resp, builtIn)
+	assert.Nil(t, err)
+	assert.Equal(t, "@here", resp.Attachments[0].Text)
 }