fix: slackToken based message returns a JSON object (#89)

This correctly handles the return type of the chat.postMessage fetch request. This also means that "success" for the two methods of sending a slack message need to be handled differently

lib/postMessage.js

@@ -8,6 +8,7 @@ module.exports = async (
 ) => {
   let response
   let bodyText
+  let isSuccess
   try {
     if (slackIcon) {
       const hasSemicolons = slackIcon.startsWith(':') && slackIcon.endsWith(':')
@@ -23,11 +24,13 @@ module.exports = async (
       response = await fetch('https://slack.com/api/chat.postMessage', {
         method: 'post',
         headers: {
-          'Content-Type': 'application/json',
+          'Content-Type': 'application/json; charset=utf-8',
           Authorization: `Bearer ${slackToken}`
         },
         body: JSON.stringify(message)
       })
+      bodyText = await response.text()
+      isSuccess = response.ok && JSON.parse(bodyText).ok
     } else {
       if (slackChannel) {
         message.channel = slackChannel
@@ -39,13 +42,14 @@ module.exports = async (
         },
         body: JSON.stringify(message)
       })
+      bodyText = await response.text()
+      isSuccess = response.ok && bodyText === 'ok'
     }
-    bodyText = await response.text()
   } catch (e) {
     throw new SemanticReleaseError(e.message, 'SLACK CONNECTION FAILED')
   }
 
-  if (!response.ok || bodyText !== 'ok') {
+  if (!isSuccess) {
     logger.log('JSON message format invalid: ' + bodyText)
     throw new SemanticReleaseError(bodyText, 'INVALID SLACK COMMAND')
   }

test/postMessage.test.js

@@ -70,12 +70,12 @@ describe('test postMessage with token/channel', () => {
   it('should pass if response is 200 "ok"', async () => {
     nock(slackPostMessageDomain)
       .post(slackPostMessagePath)
-      .reply(200, 'ok')
+      .reply(200, JSON.stringify({ ok: true }))
     assert.ifError(await postToken())
   })
 
   it('should fail if response text is not "ok"', async () => {
-    const response = 'not ok'
+    const response = JSON.stringify({ ok: false })
     nock(slackPostMessageDomain)
       .post(slackPostMessagePath)
       .reply(200, response)