我正在尝试用Slack的交互式按钮，把点击后的响应发送到我的Sinatra应用里，但始终没办法正确反序列化请求体，遇到了麻烦。

遇到的错误情况 #

当我点击Slack消息里的按钮时，Sinatra服务器抛出了这个JSON解析错误：

JSON::ParserError - unexpected token at 'payload=%7B%22type%22%3A%22block_actions%22%2C%22user%22%3A%7B%22id%22%3A%22UG0HVH1GX%22%2C%22username%22%3A%22asd%22%2C%22name%22%3A%22asd%22%2C%22team_id%22%3A%22T024GE59A%22%7D%2C%22api_app_id%22%3A%22A06F3NEL14Z%22%2C%22token%22%3A%22AYZC30arIx4CsV9AMQxU%22%2C%22container%22%3A%7B%22type%22%3A%22message%22%2C%22message_ts%22%3A%221705755611.478699%22%2C%22channel_id%22%3A%22C05GN6W4K5W%22%2C%22is_ephemeral%22%3Afalse%7D%2C%22trigger_id%22%3A%226503856512579.2152481316.74034a39fd2de763bfb820dc5060e6bb%22%2C%22team%22%3A%7B%22id%22%3A%22T024GE59A%22%2C%22domain%22%3A%22asd%22%7D%2C%22enterprise%22%3Anull%2C%22is_enterprise_install%22%3Afalse%2C%22channel%22%3A%7B%22id%22%3A%22C05GN6W4K5W%22%2C%22name%22%3A%22privategroup%22%7D%2C%22message%22%3A%7B%22type%22%3A%22message%22%2C%22subtype%22%3A%22bot_message%22%2C%22text%22%3A%22Click+Me+button%22%2C%22ts%22%3A%221705755611.478699%22%2C%22bot_id%22%3A%22B06EN64BP9B%22%2C%22blocks%22%3A%5B%7B%22type%22%3A%22actions%22%2C%22block_id%22%3A%22TMafK%22%2C%22elements%22%3A%5B%7B%22type%22%3A%22button%22%2C%22action_id%22%3A%22actionId-0%22%2C%22text%22%3A%7B%22type%22%3A%22plain_text%22%2C%22text%22%3A%22Click+Me%22%2C%22emoji%22%3Atrue%7D%2C%22value%22%3A%22click_me_123%22%7D%5D%7D%5D%7D%2C%22state%22%3A%7B%22values%22%3A%7B%7D%7D%2C%22response_url%22%3A%22https%3A%5C%2F%5C%2Fhooks.slack.com%5C%2Factions%5C%2FT024GE59B%5C%2F6516603344528%5C%2FUuYsbmvSAo56tu351G0Zl36w%22%2C%22actions%22%3A%5B%7B%22action_id%22%3A%22actionId-0%22%2C%22block_id%22%3A%22TMafK%22%2C%22text%22%3A%7B%22type%22%3A%22plain_text%22%2C%22text%22%3A%22Click+Me%22%2C%22emoji%22%3Atrue%7D%2C%22value%22%3A%22click_me_123%22%2C%22type%22%3A%22button%22%2C%22action_ts%22%3A%221705758257.494064%22%7D%5D%7D'

我当前的反序列化代码 #

我在Sinatra服务器开头加了这段反序列化的逻辑：

before do
  unless request.body.read.empty?
    request.body.rewind
    @params = Sinatra::IndifferentHash.new
    @params.merge!(JSON.parse(request.body.read))
  end
end

移除反序列化代码后的情况 #

如果我把上面这段代码删掉，用pp @params打印参数，得到的结果是：

{"payload"=>
"{\"type\":\"block_actions\",\"user\":{\"id\":\"UG0HVH1GX\",\"username\":\"asd\",\"name\":\"asd\",\"team_id\":\"T024GE59A\"},\"api_app_id\":\"A06F3NEL14Z\",\"token\":\"AYZC30arIx4CsVQxU\",\"container\":{\"type\":\"message\",\"message_ts\":\"1705755611.478699\",\"channel_id\":\"C05GN6W4K5W\",\"is_ephemeral\":false},\"trigger_id\":\"6503973207090.2152481316.8ad17fadb62def07bf15071b521180d7\",\"team\":{\"id\":\"T024GE59A\",\"domain\":\"asd\"},\"enterprise\":null,\"is_enterprise_install\":false,\"channel\":{\"id\":\"C05GN6W4K5W\",\"name\":\"privategroup\"},\"message\":{\"type\":\"message\",\"subtype\":\"bot_message\",\"text\":\"Click Me button\",\"ts\":\"1705755611.478699\",\"bot_id\":\"B06EN64BP9B\",\"blocks\":[{\"type\":\"actions\",\"block_id\":\"TMafK\",\"elements\":[{\"type\":\"button\",\"action_id\":\"actionId-0\",\"text\":{\"type\":\"plain_text\",\"text\":\"Click Me\",\"emoji\":true},\"value\":\"click_me_123\"}]}]},\"state\":{\"values\":{}},\"response_url\":\"https:\\/\\/hooks.slack.com\\/actions\\/T024GE59A\\/6501045563aa3\\/MlzRCYKujL9ETzxPJySY1v\",\"actions\":[{\"action_id\":\"actionId-0\",\"block_id\":\"TMafK\",\"text\":{\"type\":\"plain_text\",\"text\":\"Click Me\",\"emoji\":true},\"value\":\"click_me_123\",\"type\":\"button\",\"action_ts\":\"1705758480.661885\"}]}"}

同时还会收到Rack的lint错误，但负载内容其实是能拿到的：

2024-01-20 14:48:00 +0100 Rack app ("POST /reply" - (44.204.57.110)): #<Rack::Lint::LintError: Body yielded non-string value ["payload", "{"type":"block_actions","user":{"id":"UG0HVH1GX","username":"asd","name":"asd","team_id":"T024GE59A"},"api_app_id":"A06F3NEL14Z","token":"A30arIx4CsV9AM","container":{"type":"message","message_ts":"1705755611.478699","channel_id":"C05GN6W4K5W","is_ephemeral":false},"trigger_id":"6503973207090.2152481316.8ad17fadb62def07bf15071b521180d7","team":{"id":"T024GE59A","domain":"asd"},"enterprise":null,"is_enterprise_install":false,"channel":{"id":"C05GN6W4K5W","name":"privategroup"},"message":{"type":"message","subtype":"bot_message","text":"Click Me button","ts":"1705755611.478699","bot_id":"B06EN64BP9B","blocks":[{"type":"actions","block_id":"TMafK","elements":[{"type":"button","action_id":"actionId-0","text":{"type":"plain_text","text":"Click Me","emoji":true},"value":"click_me_123"}]}]},"state":{"values":{}},"response_url":"https:\/\/hooks.slack.com\/actions\/T4GE59A\/6501045552673\/MlzRCYKujL2zxPJySY1v","actions":[{"action_id":"actionId-0","block_id":"TMafK","text":{"type":"plain_text","text":"Click Me","emoji":true},"value":"click_me_123","type":"button","action_ts":"1705758480.661885"}]}"]>

现在我搞不懂这到底是怎么回事：为什么发送到response_url的请求体是这种格式？我该怎么修复才能正确解析负载内容呢？

谢谢大家！

备注：内容来源于stack exchange，提问作者Alvaro