Hey @Kunal951996, thanks for taking the time to reach out 👋🏻

Passing state data with the OAuth module is a little awkward and we're in the process of improving it (release coming soon).

For now, you will want to use the OAuth metadata feature to pass data from the install URL to the success redirect_uri. For example:

1. Create a install route such as /app/install or /slack/install (but not the built-in version)
2. Inside the route, generate a dynamic url with the user's metadata
3. Use a custom success handler to parse the metadata

A rough code sample may look like:

app.get('/slack/install', async (req, res, next) => {
  try {
    const url = await installer.generateInstallUrl({
      scopes: ['channels:read', 'groups:read', 'channels:manage', 'chat:write', 'incoming-webhook'],
      metadata: 'some_metadata',
    });

    res.send(`<a href=${url}><img alt=""Add to Slack"" height="40" width="139" src="https://platform.slack-edge.com/img/add_to_slack.png" srcset="https://platform.slack-edge.com/img/add_to_slack.png 1x, https://platform.slack-edge.com/img/add_to_slack@2x.png 2x" /></a>`);
  } catch(error) {
    console.log(error);
  }
});

const callbackOptions = {
  success: (installation, options, req, res) => {
    console.log(options.metadata);
    res.send('successful!');
  },
  failure: (error, installOptions , req, res) => {
    res.send('failure');
  },
}

app.get('/slack/oauth_redirect', async (req, res) => {
  await installer.handleCallback(req, res, callbackOptions);
});

Hope that helps!

FYI the release candidate for oauth@2.5.0-rc.1 is live on npm (you will need to install it referencing the version directly like so: npm i @slack/oauth@2.5.0-rc.1), but I will leave this issue open as I think we still need to add documentation for the new methods we have exposed in this release candidate. Once we have docs in place we will post here and close this issue.

The latest version v2.5.0 supports more callbacks to customize your OAuth flow. Refer to the "Persisting data during the OAuth flow" section in the updated document: https://slack.dev/node-slack-sdk/oauth