When upgrading from Rails 3.0 to 3.1, one of the common issues we face is the breaking change in ERB syntax for helper methods. This change impacts form_tag, form_for, content_tag, javascript_tag, fields_for, and field_set_tag.
The main issue is that these helper methods in Rails 3.1 now require the use of <%= %> to output content, whereas in Rails 3.0 (and earlier), they used <% %> without needing to explicitly output the form content. This change is not backward-compatible, and applying it across a large codebase can be quite tedious when we are using our method of dual booting an application to do an upgrade.
In this article we will explore a few possibilities we have uncovered in the past few years while doing these upgrades.
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