Lumen -> Error on line 54 - require(): Failed opening required - php

Question

I install a fresh copy of Lumen as Heroku app. Also I implemented the packange Dingo into it: https://github.com/dingo/api/ but when I try to load everything server return me this error:
2016-02-14T11:07:45.657820+00:00 app[web.1]: [14-Feb-2016 11:07:45 UTC] PHP Warning: require(/app/vendor/dingo/api/src/helpers.php): failed to open stream: No such file or directory in /app/vendor/composer/autoload_real.php on line 54
2016-02-14T11:07:45.657998+00:00 app[web.1]: [14-Feb-2016 11:07:45 UTC] PHP Fatal error: require(): Failed opening required '/app/vendor/dingo/api/src/helpers.php' (include_path='.:/app/.heroku/php/lib
/php') in /app/vendor/composer/autoload_real.php on line 54
I tried to remove vendor folder, etc and reinstall it but result is the same
EDIT: My composer.json is:
{
"name": "laravel/lumen",
"description": "The Laravel Lumen Framework.",
"keywords": ["framework", "laravel", "lumen"],
"license": "MIT",
"type": "project",
"minimum-stability": "dev",
"require": {
"php": ">=5.5.9",
"laravel/lumen-framework": "5.2.*",
"vlucas/phpdotenv": "~2.2",
"dingo/api": "1.0.x#dev"
},
"require-dev": {
"fzaninotto/faker": "~1.4",
"phpunit/phpunit": "~4.0",
"dingo/api": "1.0.x#dev"
},
"autoload": {
"psr-4": {
"App\\": "app/"
}
},
"autoload-dev": {
"classmap": [
"tests/",
"database/"
]
}
}
EDIT 2: I tried now in my local machine and Lumen with Dingo works correctly so it's something with Heroku sigh. How to see Lumen Logs in Heroku Logs?

Answer 1

I think you missed to add configuration in your Heroku App. To make your Heroku app fetching all the composer requirements, you may run this on your root of Lumen App:
heroku config:add BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-php
Make a change again, then push your changes to heroku repository, eg:
git push heroku master
Edit
To make this works, I have my own way to deploy Lumen App to Heroku.
lumen new my-app
cd my-app
# Here you can change your composer.json dependencies
composer require dingo/api
Make your procfile
vim Procfile
# Content of Procfile
web: vendor/bin/heroku-php-apache2 public
Initialize repo
git init
git add -A .
git commit -m "[INIT] Initial commit."
Create Heroku app:
heroku create
heroku config:add BUILDPACK_URL=https://github.com/heroku/heroku-buildpack-php
git push heroku master
Visit your heroku app.