Custom dialect missing attributes

Hi, I am creating a custom tags using thymeleaf 3. Initially it is created in thymeleaf 2, but since we are upgrading to versioin 3 we need to rewrite our current custom tags.

We had some issue related to th:field attributes (and other th:* commands). Upon accessing the custom element itself the supposed generated name and value field from th:field is not there or even a th:field itself. Our custom tag has higher precedence than the th:* tags as we would like to retrieve the generated value. Below is from our logs:

HTML <extra:file th:document="${document}" th:field="*{regFile}" class="form-control" th:text="${docId}"></extra:file>

LOGS

_This part is retrieved from the ITemplateContext.getElementStack -_
FileTagProcessor.doProcess:101 - getElementCompleteName---------------------------->extra:file
FileTagProcessor.doProcess:106 - getAttributeMap: {th:document=${document}, th:field=*{regFile}, class=form-control, th:text=${docId}} 

_This is retrieved from IProcessableElementTag_
FileTagProcessor.doProcess:109 - getAttributeMap: {document={"docTypeId":180,"docDesc":{"en":"Upload File"},"order":1,"type":"image/gif, image/jpeg, image/png, application/pdf","size":1000000,"compulsary":true,"dimensionCompulsary":false}, class=form-control} - {} 
FileTagProcessor.doProcess:112 - IAttribute---------------------------->document="{"docTypeId":180,"docDesc":{"en":"Upload File"},"order":1,"type":"image/gif, image/jpeg, image/png, application/pdf","size":1000000,"compulsary":true,"dimensionCompulsary":false}"
FileTagProcessor.doProcess:112 - IAttribute---------------------------->class="form-control"
FileTagProcessor.doProcess:116 - label: {"docTypeId":180,"docDesc":{"en":"Upload File"},"order":1,"type":"image/gif, image/jpeg, image/png, application/pdf","size":1000000,"compulsary":true,"dimensionCompulsary":false}
FileTagProcessor.doProcess:120 - label: 180

Extra Dialect precedence is 100000 File Tag precedence is 2147483647

[ultraq]

Ah, yes having a higher precedence than the standard dialect will mean you miss out on seeing things like th:field in its raw state 🤔

Some workarounds that I can think of:

• create a separate dialect with a lower value than the standard dialect, which then that contains the processor you want to see the th:field value
• create another processor that can be included on a parent HTML element, like the <form>, and then search through all of its input elements to find the th:field attributes you want to work with

[ultraq]

my expectation is it will generate the corresponding attribute id and name generated by th:field

So th:field will do that, but it’ll have to be on an HTML input element that it knows about, not a custom one like <extra:file>.

Given this, one option to try is to change from using a custom element to a custom attribute, use an HTML input element so that th:field can add the id and name as it normally would, then your attribute processor can read those values from the element after, eg:

<input type="file" th:field="*{regFile}" ... extra:file>

(I can’t remember if you can have custom attributes without values. If not, then making it extra:file="" should fix that up.)

th:field will recognize <input type="file"> and add the appropriate id and name attributes, then your extra:file attribute processor can read them from the input element.