RESTEasy Reactive Multipart Json Upload doesn't work for files

[andreas-eberle]

Describe the bug

I try to use RestEasy Reactive's Multipart upload to upload a json file and want to get the parsed contents in my multipart Dto. This works fine if directly send json in the part but it doesn't work if the part is a file containing json.

Expected behavior

Should be the same for json files and for "inline" json.

Actual behavior

No response

How to Reproduce?

Reproducer:
2021-08-26_resteasy-reactive-multipart-json-file.zip

1. Download, unzip, start with ./gradlew quarkusDev
2. Run curl command curl --location --request POST 'localhost:8080/hello' --form 'jsonFilePart=@"./multipart-test.json";type=application/json' --form 'jsonPart="{\"name\": \"Json without file part\" }";type=application/json' (the file multpart-test.json is included in the reproducer project)
3. You will get a response like this {"jsonFilePart":null,"jsonPart":{"name":"Json without file part"}}
4. Expected result: The jsonFilePart contains the contents of the multipart-test.json file.

Output of uname -a or ver

No response

Output of java -version

No response

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.1.3

Build tool (ie. output of mvnw --version or gradlew --version)

gradle

Additional information

No response

[quarkus-bot]

/cc @FroMage, @geoand, @stuartwdouglas

[geoand]

This is the expected behavior actually.

When you upload a file, the field is not populated with the value. Instead, you should use FileUpload as the field type.

The fact that there is no actionable information however is not ideal. I'll look into adding something

[geoand]

#19684 adds a debug log message for this case