feat: slack app addon default channels (#4308)

https://linear.app/unleash/issue/2-1249/add-support-for-default-slack-channels

Adds support for default Slack channels (multiple, comma-separated). 

Some of the events we are handling do not have associated tags, or maybe
the tags are empty. This adds a "default Slack channels" parameter to
the addon configuration in order to post messages to those channels in
those cases.

<img width="643" alt="image"
src="https://github.com/Unleash/unleash/assets/14320932/ee23d6c7-33b7-4968-a0b1-13b546b5b2a2">

---------

Co-authored-by: Gastón Fournier <gaston@getunleash.io>

src/lib/addons/__snapshots__/slack-app.test.ts.snap

@@ -83,3 +83,45 @@ exports[`SlackAppAddon should post to all channels in tags 2`] = `
   "text": "some@user.com *enabled* <http://some-url.com/projects/default/features/some-toggle|some-toggle> in *development* environment in project *default*",
 }
 `;
+
+exports[`SlackAppAddon should use defaultChannels if no tagged channels are found 1`] = `
+{
+  "attachments": [
+    {
+      "actions": [
+        {
+          "name": "featureToggle",
+          "style": "primary",
+          "text": "Open in Unleash",
+          "type": "button",
+          "url": "http://some-url.com/projects/default/features/some-toggle",
+          "value": "featureToggle",
+        },
+      ],
+    },
+  ],
+  "channel": 1,
+  "text": "some@user.com *enabled* <http://some-url.com/projects/default/features/some-toggle|some-toggle> in *development* environment in project *default*",
+}
+`;
+
+exports[`SlackAppAddon should use defaultChannels if no tagged channels are found 2`] = `
+{
+  "attachments": [
+    {
+      "actions": [
+        {
+          "name": "featureToggle",
+          "style": "primary",
+          "text": "Open in Unleash",
+          "type": "button",
+          "url": "http://some-url.com/projects/default/features/some-toggle",
+          "value": "featureToggle",
+        },
+      ],
+    },
+  ],
+  "channel": 2,
+  "text": "some@user.com *enabled* <http://some-url.com/projects/default/features/some-toggle|some-toggle> in *development* environment in project *default*",
+}
+`;

src/lib/addons/slack-app-definition.ts

@@ -48,6 +48,15 @@ const slackAppDefinition: IAddonDefinition = {
             required: true,
             sensitive: true,
         },
+        {
+            name: 'defaultChannels',
+            displayName: 'Default channels',
+            description:
+                'A comma-separated list of channels to post to if no tagged channels are found (e.g. a toggle without tags, or an event with no tags associated).',
+            type: 'text',
+            required: false,
+            sensitive: false,
+        },
     ],
     events: [
         FEATURE_CREATED,

src/lib/addons/slack-app.test.ts

@@ -79,6 +79,7 @@ describe('SlackAppAddon', () => {
         jest.useFakeTimers();
         slackApiCalls.length = 0;
         conversationsList.mockClear();
+        postMessage.mockClear();
         addon = new SlackAppAddon({
             getLogger,
             unleashUrl: 'http://some-url.com',
@@ -153,6 +154,37 @@ describe('SlackAppAddon', () => {
         expect(conversationsList).toHaveBeenCalledTimes(2);
     });
 
+    it('should not post a message if there are no tagged channels and no defaultChannels', async () => {
+        const eventWithoutTags: IEvent = {
+            ...event,
+            tags: [],
+        };
+
+        await addon.handleEvent(eventWithoutTags, {
+            accessToken,
+        });
+
+        expect(slackApiCalls.length).toBe(0);
+    });
+
+    it('should use defaultChannels if no tagged channels are found', async () => {
+        const eventWithoutTags: IEvent = {
+            ...event,
+            tags: [],
+        };
+
+        await addon.handleEvent(eventWithoutTags, {
+            accessToken,
+            defaultChannels: 'general, another-channel-1',
+        });
+
+        expect(slackApiCalls.length).toBe(2);
+        expect(slackApiCalls[0].channel).toBe(1);
+        expect(slackApiCalls[0]).toMatchSnapshot();
+        expect(slackApiCalls[1].channel).toBe(2);
+        expect(slackApiCalls[1]).toMatchSnapshot();
+    });
+
     it('should log error when an API call fails', async () => {
         postMessage = jest.fn().mockRejectedValue(mockError);
 

src/lib/addons/slack-app.ts

@@ -25,6 +25,7 @@ const CACHE_SECONDS = 30;
 
 interface ISlackAppAddonParameters {
     accessToken: string;
+    defaultChannels: string;
 }
 
 export default class SlackAppAddon extends Addon {
@@ -52,17 +53,20 @@ export default class SlackAppAddon extends Addon {
         parameters: ISlackAppAddonParameters,
     ): Promise<void> {
         try {
-            const { accessToken } = parameters;
+            const { accessToken, defaultChannels } = parameters;
             if (!accessToken) {
                 this.logger.warn('No access token provided.');
                 return;
             }
 
             const taggedChannels = this.findTaggedChannels(event);
-            if (!taggedChannels.length) {
+            const eventChannels = taggedChannels.length
+                ? taggedChannels
+                : this.getDefaultChannels(defaultChannels);
+
+            if (!eventChannels.length) {
                 this.logger.debug(
-                    `No Slack channels tagged for event ${event.type}`,
+                    `No Slack channels found for event ${event.type}.`,
-                    event,
                 );
                 return;
             }
@@ -99,7 +103,7 @@ export default class SlackAppAddon extends Addon {
             const url = this.msgFormatter.featureLink(event);
 
             const slackChannelsToPostTo = currentSlackChannels.filter(
-                ({ id, name }) => id && name && taggedChannels.includes(name),
+                ({ id, name }) => id && name && eventChannels.includes(name),
             );
 
             const requests = slackChannelsToPostTo.map(({ id }) =>
@@ -151,6 +155,13 @@ export default class SlackAppAddon extends Addon {
         return [];
     }
 
+    getDefaultChannels(defaultChannels?: string): string[] {
+        if (defaultChannels) {
+            return defaultChannels.split(',').map((c) => c.trim());
+        }
+        return [];
+    }
+
     startCacheInvalidation(): void {
         this.slackChannelsCacheTimeout = setInterval(() => {
             this.slackChannels = undefined;