SpringBoot 4.0.3, Spring webmvc 7.0.5, ResponseBodyEmitterReturnValueHandler duplicates headers when there is no emitter

[jaxdax873-code]

In ResponseBodyEmitterReturnValueHandler method handleReturnValue
There is new logic when emitter is null

outputMessage.getHeaders().forEach((headerName, headerValues) -> {
                    for (String headerValue : headerValues) {
                        response.addHeader(headerName, headerValue);
                    }
                });

This place duplicate headers from outputMessage to response

In CORSE case it will create not valid response headers with duplicate.
Is it new logic or bug ? At the moment can be solved with Filters not allowing add duplicates.

[bclozel]

@jaxdax873-code maybe you can share a minimal sample application? This would help us figure out whether this is a bug or expected behavior.

[rstoyanchev]

Possibly a duplicate of #36357. Could you try with 7.0.6-SNAPSHOT?

[spring-projects-issues]

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