fix: Avoid truncating in the middle of markdown (#20)

.circleci/config.yml

@@ -24,6 +24,9 @@ jobs:
       - run:
           name: Lint test
           command: npm run lint
+      - run:
+          name: Run tests
+          command: npm test
   deploy:
     docker:
       - image: circleci/node:10.5.0

lib/success.js

@@ -2,6 +2,7 @@
 const slackifyMarkdown = require('slackify-markdown')
 const postMessage = require('./postMessage')
 const template = require('./template')
+const truncate = require('./truncate')
 
 // Max lenght of message to the slack api is 3000 characters. Make sure we are below that.
 const MAX_LENGTH = 2900
@@ -57,10 +58,7 @@ module.exports = async (pluginConfig, context) => {
 
 		if (nextRelease.notes !== '') {
 			// truncate long messages
-			let messageText =
-				nextRelease.notes.length > MAX_LENGTH
-					? nextRelease.notes.substring(0, MAX_LENGTH) + '*[...]*'
-					: nextRelease.notes
+			let messageText = truncate(nextRelease.notes, MAX_LENGTH)
 
 			if (pluginConfig.markdownReleaseNotes)
 				messageText = slackifyMarkdown(messageText)

lib/truncate.js

@@ -0,0 +1,14 @@
+module.exports = (messageText, maxLength) => {
+	const delimiter = '\n'
+	if (messageText.length > maxLength) {
+		messageText = messageText.substring(0, maxLength).split(delimiter)
+		// if no newlines, we don't remove anything, we keep the truncated message as is
+		if (messageText.length > 1) {
+			// remove all text after the last newline in the truncated message
+			// this avoids truncating in the middle of markdown
+			messageText.splice(-1, 1)
+		}
+		messageText = messageText.join(delimiter) + '*[...]*'
+	}
+	return messageText
+}