PATCH cannot use "op": "test" on enum values

[ebrannin-bw]

Description

HTTP PATCH requests with an "op": "test" operation on an enum field always fail because the JSON String's String value is compared to the enum's enum-type value.

(In all versions checked: probably-latest of each Spring Boot 3.x and 4.0, 4.1)

Steps to Reproduce

Minimally-reproducing test repository, against each of Spring Boot 3.{0-5} and 4.{0-1}:

https://github.com/ebrannin-bw/spring-patch-test-enum-bug-report

(The above repo is mostly Claude-written. This issue is human-written, except for the code-blocks, which were either from the Claude-written test code or copied from test output.)

Data Class

(With Lombok)

@Entity
@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class Widget {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private Integer amount;

    @Enumerated(EnumType.STRING)
    @Column(columnDefinition = "varchar(255)")
    private JobStatus status;
}

Basic JpaRepository

@RepositoryRestResource
public interface WidgetRepository extends JpaRepository<Widget, Long> {
}

Request payload

[
  { "op": "test",    "path": "/status", "value": "NEW" },
  { "op": "replace", "path": "/name",   "value": "Updated Widget" }
]

Expected Result

The PATCH succeeds if widget.getStatus() == NEW

Observed Result

The PATCH always fails, with a stack trace like this:

org.springframework.http.converter.HttpMessageNotReadableException: Could not read an object of type class com.example.spring.patch.enumbug.Widget from the request
	at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.readPatch(PersistentEntityResourceHandlerMethodArgumentResolver.java:226) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.lambda$read$0(PersistentEntityResourceHandlerMethodArgumentResolver.java:196) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at java.base/java.util.Optional.map(Optional.java:260) ~[na:na]
	at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:193) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.resolveArgument(PersistentEntityResourceHandlerMethodArgumentResolver.java:136) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	...
Caused by: org.springframework.data.rest.webmvc.json.patch.PatchException: Test against path '/status' failed
	at org.springframework.data.rest.webmvc.json.patch.TestOperation.perform(TestOperation.java:78) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.json.patch.Patch.apply(Patch.java:66) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.config.JsonPatchHandler.applyPatch(JsonPatchHandler.java:94) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.config.JsonPatchHandler.apply(JsonPatchHandler.java:82) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.readPatch(PersistentEntityResourceHandlerMethodArgumentResolver.java:217) ~[spring-data-rest-webmvc-5.1.0.jar:5.1.0]
	... 113 common frames omitted