gsp-double-encoding

This domo shows strange behavior of Grails 4 GSP double encoding prevention.

Build an run

$ ./gradlew bootRun

Browse to http://localhost:8080/demo

Problem

Steps to Reproduce

1. Create new Grails 4 app via IntelliJ IDEA
2. Create Controller: put two Strings amp1: '&' and amp2: '&'.encodeAsHTML() to the model
3. Create GSP-View: output each String with ${…} and ${raw(…)} and test the Strings in the view for equality.
4. don't change any default settings

Expected Behaviour

• all outputs of the strings in the model are equal
• … exactly if amp1 == amp2 is true

Actual Behaviour

• amp1 == amp2 is true according to <g:if>
• &{amp1} is outputted as & in the HTML source → shows up in the browser as "&"
• &{amp2} is outputted as &in the HTML source → shows up in the browser as "&"

Documentation to double encoding prevention:

Grails 2.3 includes double encoding prevention so that when an expression is evaluated, it will not encode if the data has already been encoded (Example ${foo.encodeAsHTML()}).

—https://docs.grails.org/latest/guide/security.html#_double_encoding_prevention