Multipart messages with empty parts are not correctly parsed in WebFlux

[KrisDaCoder]

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In my application spring boot webflux application I have an upload use case which requires the upload of 1 and more empty files. The upload endpoint is pretty simple in itself and goes like this:

public Mono<ResponseEntity<ResponseDTO>> upload(@RequestPart("files") Flux<FilePart> fileParts) {
    // fileParts.flatMap(filePart -> will only contain the last empty file always if more than one empty file is uploaded)
}

The problem is that if more than 1 empty files are uploaded, then only the last one is considered.

This issue started when upgrading from spring boot 2.7.18 to 3.3.5.

I saw a similar issue to this https://github.com/spring-projects/spring-framework/issues/30953 which has already been closed but I'm still having something similar. I tried though to reproduce it using the webTestClient in an automated test but to no avail. Maybe this explains https://github.com/spring-projects/spring-framework/issues/30953.

[bclozel]

Sorry for the delayed response. I've had a look at https://github.com/spring-projects/spring-framework/issues/30953 and I'm not seeing any obvious reason that would explain this behavior. The test added with that fix does contain multiple empty parts.

I tried though to reproduce it using the webTestClient in an automated test but to no avail.

Maybe you can reproduce this with a curl request, or an HTML page with a browser? In any case, we're going to need something that reproduces the problem otherwise we won't be able to find out the root of the problem.

Thanks!

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