title: How does one conditionally get null as a default value in cookiecutter prompts?
body: <p>Here is my example cookiecutter.json and Jinja logic</p>
  <pre class="lang-json prettyprint-override"><code>{
      &quot;pick_one&quot;: [
          &quot;Choice A&quot;,
          &quot;Choice B&quot;
      ],
      &quot;user_name&quot;: &quot;{%- if cookiecutter.pick_one == 'Choice A' -%} mydefault {%- else -%}  null {%- endif -%}&quot;,
      &quot;full_name&quot;: null
  }
  </code></pre>
  <p>Notice that <code>full_name</code>'s default value is null, and this means an entry from the user is required.</p>
  <p>For <code>user_name</code>, I'd like to have one default based on the <code>pick_one</code> value or null if not that value. In other words,  If Choice A is selected, I'd like the default to be <code>mydefault</code> and if not, I'd like null to be the default and <code>user_name</code> to work the same as <code>full_name</code> does in the example.</p>
  <p>So far, I've tried wrapping null in curly braces, added safe to it.
  <code>{{ null }}</code> or <code>{{ null | safe }}</code> but I get an error that the variable cannot be rendered because 'null' is undefined.
  In other attempts, I get the string &quot;null&quot; as a default instead of requiring the user to enter a value.</p>
  <p>Thanks so much!</p>