Header may not contain more than a single header, new line detected error with `redirect` tag

Question

I have this in a template:

{% import "_helpers/macros" as macros %}
{% set redirectUrl = macros.testRelatedReview(entry) %}
{% redirect redirectUrl 301 %}

The macro returns an entry URL.

But the page returns an error:

Header may not contain more than a single header, new line detected

If I change it to {% redirect 'actual_value_of_redirectUrl' 301 %}, it redirects OK.

How do I get it to work with the dynamic variable though?

Answer 1

new line detected should give you an idea of what to look for - your macro file may have some line breaks between code blocks, and it's writing them to the page before hitting your redirect tag. Try wrapping it all in {% spaceless %} tags, and see if that helps?