Running pact test with a matcher in request body returns a Server Error from mock server

[surpher]

🌎 Environment

• Platform: PactSwift
• pact-reference: libpact_mock_server_ffi built from master (cargo build --release)

💬 Description

When writing a pact test where the request body includes a matcher, the response from mock server is Server Error, status code: 500.

Update:
Happens with POST and request body without a matcher too, but when I used PUT and passed a a request body without a matcher, I received a 201 response as expected.
No change even when specifically defining the request's expected headers to be Content-Type: application/json.

🦶 Reproduction Steps

Steps to reproduce the behavior:

1. Prepare a unit test that generates a Pact object where a matcher is in the request body
2. Pass Pact object to libpact_mock_server_ffi
3. Trigger network request to test the interaction

🤔 Expected Results

The response from mock server returns the value provided in the matcher and status code as defined in pact test.

😲 Actual Results

The response from mock server returns 500 - Server Error.

🌳 Logs

Pact object sent to libpact_mock_server_ffi.create_mock_server()

{
	"metadata": {
		"PactSwift": { "version": "0.0.0" },
		"pactSpecification": { "version": "3.0.0" }
	},
	"interactions": [{
		"response": {
			"status": 201
		},
		"providerState": "users does not exist",
		"request": {
			"path": "\/user",
			"body": {
				"name": "Joe"
			},
			"method": "post",
			"matchingRules": {
				"body": {
					"$.name": {
						"matchers": [{
							"match": "type"
						}]
					}
				}
			}
		},
		"description": "Request to create a user"
	}],
	"provider": { "name": "unit-test-api-provider" },
	"consumer": { "name": "pactswift-unit-tests" }
}

📄 Stack Traces

n/a

🤝 Relationships

• Related PRs or Issues:

[surpher]

Update, perhaps it has to do with existing Pact file in PACT_OUTPUT_DIR?
Or maybe having multiple tests setup with same path, query and body but different method?

The following test written in PactSwift passes just fine:

    func testMockService_Succeeds_ForPOSTRequestWithMatchersInRequestBody() {
		mockService
			.uponReceiving("Request to create a new user")
			.given("user does not exist")
			.withRequest(
				method: .POST,
				path: "/user/add",
				query: nil,
				headers: ["Content-Type": "application/json"],
				body: [
					"name": Matcher.SomethingLike("Joe"),
				        "age": Matcher.IntegerLike(42)
				 ]
			)
			.willRespondWith(
				status: 201
			)

		let testExpectation = expectation(description: #function)

		mockService.run { completion in
			let requestURL = URL(string: "\(self.mockService.baseUrl)/user/add")!
			let session = URLSession.shared
			var request = URLRequest(url: requestURL)

			request.httpMethod = "POST"
			request.setValue("application/json", forHTTPHeaderField: "Content-Type")
			request.httpBody = #"{"name":"Joseph","age":24}"#.data(using: .utf8)

			let task = session.dataTask(with: request) { data, response, error in
				if let response = response as? HTTPURLResponse {
					XCTAssertEqual(response.statusCode, 201)
				}
				testExpectation.fulfill()
				completion()
			}
			task.resume()
		}

		waitForExpectations(timeout: 1)
	}

[uglyog]

This might be affected by #77, if there was an existing pact file, it would not have been merged correctly.