Problem

The "Export Gist" button on https://run.dlang.io/ fails with a 500 Internal Server Error when clicked.

Steps to Reproduce

1. Go to https://run.dlang.io/
2. Write any D code in the editor
3. Click the "Export Gist" button

Console Error

POST https://run.dlang.io/api/v1/gist 500 (Internal Server Error)
angular.js:12722 TypeError: Cannot read properties of undefined (reading 'htmlUrl')
    at tour-controller.js:383:21
    at angular.js:14991:28
    at r.$eval (angular.js:16251:16)
    at r.$digest (angular.js:16069:15)
    at r.$apply (angular.js:16359:13)
    at g (angular.js:10791:36)
    at R (angular.js:10989:7)
    at v.onload (angular.js:10930:9)

Root Cause

After reviewing the code, the issue appears to be caused by a missing or invalid GITHUB_TOKEN environment variable on the production server.

Code Flow:

1. Backend (source/rest/apiv1.d:146-160) attempts to create a GitHub Gist
2. The authorization header uses githubToken which comes from environment variable
3. If empty/invalid, GitHub API returns 401 Unauthorized
4. Backend catches this and returns 500 error: "GitHub API not available"
5. Frontend (public/static/js/tour-controller.js:381-384) receives undefined data and crashes trying to access data.htmlUrl

Proposed Fix

Set the GITHUB_TOKEN environment variable on the production server as documented in README.md (lines 144-148):

GITHUB_TOKEN

default: (empty)

Required for exporting Gists to GitHub.
Follow these instructions to generate a CLI GitHub token.

Additional Improvements (Optional)

1. Improve frontend error handling to gracefully handle API failures instead of crashing
2. Add startup validation to warn when GITHUB_TOKEN is not configured
3. Show user-friendly error messages when the feature is unavailable

Status of "Shorten" Button

Unknown - needs testing to confirm if it's also affected by similar issues with the is.gd service.