Pact verification of response body with line breaks fails (JUnit5)

[mhnot]

I tried to cover a file download endpoint via consumer driven contract test.
I don't care about the downloaded content but want to verify that the body is not empty by using PactDslRootValue.stringMatcher("^.+$", "whatever")

Consumer class:

public class DownloadEndpointsCDCTest extends ConsumerPactTest
{
  @Override
  protected RequestResponsePact createPact(final PactDslWithProvider aBuilder)
  {
    return aBuilder//
        .given("A text generation job finished successfully")
        .uponReceiving("A request to download text")
        .pathFromProviderState("/textresult/${jobId}", "/textresult/" + "dummyJobId")
        .method("GET")
        .willRespondWith()
        .status(200)
        .headers(Map.of("Content-Type", "text/plain"))
        .body(PactDslRootValue.stringMatcher("^.+$", "whatever"))
        .toPact();
  }
}

Generated contract:

{
  "consumer": {
    "name": "Core_Chat_Client"
  },
  "interactions": [
    {
      "description": "A request to download text",
      "providerStates": [
        {
          "name": "A text generation job finished successfully"
        }
      ],
      "request": {
        "generators": {
          "path": {
            "dataType": "STRING",
            "expression": "/textresult/${jobId}",
            "type": "ProviderState"
          }
        },
        "method": "GET",
        "path": "/textresult/dummyJobId"
      },
      "response": {
        "body": "whatever",
        "headers": {
          "Content-Type": "text/plain"
        },
        "matchingRules": {
          "body": {
            "$": {
              "combine": "AND",
              "matchers": [
                {
                  "match": "regex",
                  "regex": "^.+$"
                }
              ]
            }
          }
        },
        "status": 200
      }
    }
  ],
  "metadata": {
    "pact-jvm": {
      "version": "4.3.10"
    },
    "pactSpecification": {
      "version": "3.0.0"
    }
  },
  "provider": {
    "name": "Chat_Service"
  }
}

Unfortunately the verification on provider side fails in case body contains line breaks.
The body content "Hello World" can be verified successfully but "Hello \r\n World" fails with following message:

java.lang.AssertionError: Core_Chat_Client - Upon A request to download text
Failures:

1. Verifying a pact between Core_Chat_Client and Chat_Service - A request to download text has a matching body

   1.1) body: / Expected body 'whatever' to match 'Hello
   World' using regex '^.+$' but did not match
   at au.com.dius.pact.provider.junit5.PactVerificationContext.verifyInteraction(PactVerificationContext.kt:66)
   at foo.ContractVerificationTest.pactVerificationTestTemplate(ContractVerificationTest.java:147)

Used versions:
Consumer: au.com.dius.pact.consumer:junit:4.3.10
Provider: au.com.dius.pact.provider:junit5:4.3.10