Lookup Slack users by Github username

We have a collection of GitHub Actions that can be used to implement common Workflows to improve the efficiency of your projects. Alongside these Actions are also pre-configured Workflows that implement the most common of these, for your convenience.

View the innovation-shared-actions repository (internal).

Slack User Lookup Action

This github action can be used to find the Slack users associated with a list of GitHub usernames. It’s intended to utilize an org-level variable in GitHub that stores the mappings of GitHub usernames to Slack user IDs.

How it works

The action simply receives a list of github usernames and for any matches inside the provided mapping, returns a correctly formatted slack mention for use in another action, such as the Send Slack Message. For any usernames that it doesn’t find a match for, it returns them separately, untouched. For convenience it also outputs all matched and unmatched usernames as a formatted, comma-delimited string.

Inputs

Name	Required	Type	Description
`github_usernames`	Yes	string	Space-delimited string of GitHub users to lookup.
`github_slack_mapping`	Yes	string	A raw JSON string that represents a mapping of GitHub username keys to Slack User ID values. Most of the time you’ll want to use our preconfigured org variable, `GH_SLACK_USER_MAP`.

Outputs

Name	Description
`slack_users`	JSON array of Slack user IDs that were matched
`github_users`	JSON array of GitHub usernames that couldn’t be matched
`formatted_string`	Comma-separated string of formatted mentions (Slack users as <@ID>, unmatched GitHub users as @username)

Using this action in your repository

name: "Custom Slack Workflow"

on:
  workflow_dispatch:

jobs:
  custom-notification:
    runs-on: ubuntu-latest
    steps:
      - name: Send Slack message
        id: slack-lookup
        uses: newjersey/innovation-shared-actions/.github/actions/lookup-slack-users@main
        with:
          github_usernames: "jviall aloverso"
          github_slack_mapping: ${{ vars.GH_SLACK_USER_MAP }}

      - name: Format the output
        id: format
        shell: bash
        run: |
          # Build formatted string with mentions
          SLACK_MENTIONS=$(echo "$SLACK_USERS" | jq -r -s '(.[0] | map("<@" + . + ">")) | join(", ")')
          echo "slack_mentions=$SLACK_MENTIONS" >> $GITHUB_OUTPUT

      - name: Use the result in a slack message with mentions
        id: send-slack-message
        uses: newjersey/innovation-shared-actions/.github/actions/slack-message@main
        with:
          channel_id: C09Q34G9HMX
          message: "These are all the Slack users I found: ${{ steps.format.outputs.slack_mentions }}"
          thread_message: "And here's everyone, matched or not: ${{ steps.slack-lookup.outputs.formatted_string}}. So easy to use cause I didn't have to format them myself!"
          token: ${{ secrets.SLACK_OAUTH_TOKEN }}