Allow fragment parameters to have default values

It would be great if fragment parameters could have default values:

<div th:fragment="frag (param = 'hello')">

[danielfernandez]

@git2snap the idea is that, at the fragment side, a th:with can assign a default value to a parameter that is not given it (or is null).

Note that parameters appearing in the signature (frag(par1,par2)) are required, so we would have two options:

First option:

<div th:fragment="frag (one)" th:with="two=${two} ?: 'default'">...</div>

Which we could call in several ways (note using named parameters as in the last line we can include parameters that are not in the signature):

<div th:replace="::frag(${onevalue})">...</div>
<div th:replace="::frag(one=${onevalue})">...</div>
<div th:replace="::frag(one=${onevalue},two=${twovalue})">...</div>

Second option:

<div th:fragment="frag (one,two)" th:with="two=${two} ?: 'default'">...</div>

Which requires us to specify both parameters (nulling the second one if needed):

<div th:replace="::frag(${onevalue},${twovalue})">...</div>
<div th:replace="::frag(${onevalue},${null})">...</div>
<div th:replace="::frag(one=${onevalue},two=${twovalue})">...</div>
<div th:replace="::frag(one=${onevalue},two=${null})">...</div>

[danielfernandez]

@JavaWebinar please note that th:replace has greater precedence than th:with, so in your tag:

<div th:replace="fragments::headTag('title')" th:with="img='value'">

That th:replace will execute, replace the tag, and therefore make that th:with simply disappear. So it will never execute and your img local variable will be never given a value.

If you want to specify that additional parameter, you can do:

<div th:replace="fragments::headTag(title='title',img='value')">