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th:hasErrors() creates model attributes if not present (side-effect) [SPR-17567] #22099

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spring-issuemaster opened this issue Dec 5, 2018 · 0 comments

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@spring-issuemaster spring-issuemaster commented Dec 5, 2018

Nicolai Ehemann opened SPR-17567 and commented

I'm not 100% sure this is a problem of spring core or perhaps thymeleaf (due to my lack of knowledge of internals), but I suspect the problem is actually with spring:

Calling th:hasErrors() in a thymeleaf template can have the potentially unwanted side-effect of creating model attributes while evaluating the thymeleaf template.

One way I found to reproduce this is using uninitialized nested model attributes. If I have a model attribute that has another object as a field, and that field is not initialized per construction, it will be initialized upon calling th:hasErrors() on it.

For example, I have a model attribute person with a field address which in turn has a field street. Consider the following thymeleaf snippet:

<div th:object="${person}>
  <span th:text="*{address}"/><!-- adress is null -->
  <span th:text="${#fields.hasErrors('address.street')}"/>
  <span th:text="*{address}"/><!-- adress is now an object -->
</div>

I don't think hasErrors() should have such unexpected side effects.

I made a minimal modification to the spring example project gs-validating-form-input to demonstrate/reproduce the issue: McNetic/gs-validating-form-input@55a265f
 

(I know the examples are not very meaningful)


Affects: 5.1.2

Reference URL: McNetic/gs-validating-form-input@55a265f

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