title: Terraform / Heroku not finding 'web' process in heroku/ruby buildpack
body: <p>I'm getting an error in Terraform:</p>
  <blockquote>
  <p>Error: Patch &quot;https://api.heroku.com/apps/coderdojo-contentful-staging/formation/web&quot;: Couldn't find that process type (web).<br />
  │<br />
  │ with heroku_formation.coderdojo_contentful_staging_formation[0],<br />
  │ on terraform.tf line 41, in resource &quot;heroku_formation&quot; &quot;coderdojo_contentful_staging_formation&quot;:<br />
  │ 41: resource &quot;heroku_formation&quot; &quot;coderdojo_contentful_staging_formation&quot; {</p>
  </blockquote>
  <p>from these lines from my <code>terraform.tf</code> file:</p>
  <pre class="lang-terraform prettyprint-override"><code>resource &quot;heroku_formation&quot; &quot;coderdojo_contentful_staging_formation&quot; {
    count    = length(var.formations)
    app      = heroku_app.coderdojo_contentful_staging.name
    type     = lookup(var.formations[count.index], &quot;type&quot;)
    quantity = lookup(var.formations[count.index], &quot;quantity&quot;)
    size     = lookup(var.formations[count.index], &quot;size&quot;)
  }
  </code></pre>
  <p>which rely on these lines in my <code>terraform.tfvars</code> file:</p>
  <pre class="lang-terraform prettyprint-override"><code>formations = [
    {
      type     = &quot;web&quot;
      size     = &quot;standard-1x&quot;
      quantity = &quot;1&quot;
    }
  ]
  
  buildpacks = [
    &quot;heroku/ruby&quot;
  ]
  </code></pre>
  <p>Searching the documentation online (e.g. <a href="https://devcenter.heroku.com/articles/buildpacks" rel="nofollow noreferrer">buildpacks</a> and <a href="https://elements.heroku.com/buildpacks/heroku/heroku-buildpack-ruby" rel="nofollow noreferrer">heroku-buildpack-ruby</a>) it appears that the web process type comes from either the buildpack, or the <code>Procfile</code>.</p>
  <p>Another project works fine with a very similar setup (i.e. no <code>Procfile</code>), but with the addition of a <code>heroku/nodejs</code> buildpack. I tried adding that build pack but got the same error.</p>
  <p>What am I missing?</p>