Dap4 Error responses are not correctly chunked.

[ndp-opendap]

When the Hyrax service encounters a user error (ex. no such variable) the response is not DAP4 chunked, it is a naked XML document containing. DAP4 error object.

The response SHOULD contain a chunk header whose flags are set to error=true, last_chunk=true, followed by the length of the error object content.

[Mikejmnez]

minimal example:

The following URL is wrong, and using curl as follows:

curl -i -L "http://test.opendap.org:8080/opendap/dap4/SimpleGroup.nc4.h5.dap?dap4.ce=/SimpleGroup/Salinity%5B0:1:0%5D"

yields:

HTTP/1.1 400
Content-Description: DAP4 Error Object
vary: accept-encoding
Content-Type: application/vnd.opendap.dap4.error.xml
Transfer-Encoding: chunked
Date: Wed, 18 Dec 2024 21:02:59 GMT
Connection: close

<?xml version="1.0" encoding="UTF-8"?>
<dap4:Error xmlns:dap4="http://xml.opendap.org/ns/DAP/4.0#" httpcode="400">
  <dap4:Message>libdap error transmitting DAP4Data: The index constraint for 'Salinity' does not match its rank.</dap4:Message>
  <dap4:Context />
  <dap4:OtherInformation />
</dap4:Error>

Expected behavior for that error

The body of the response should be prefixed by a chunk header with the following hex value: 03000138.

where:

• 03 : indicates an error chunk, and last chunk
• 000138: length in hex of the error document