Validate min = 0

[tienvx]

According to https://docs.pact.io/faq#why-is-there-no-support-for-specifying-optional-attributes, array with min=0 is not supported at all.

... This is why you can only specify an array with minimum length 1 OR a zero length array.

But I still can set min = 0 in consumer test. Pact file is generated. Provider verification is passed if attribute/field is empty array. Here is how I did it:

Instead of using eachLike in pact-js, I replace it with custom code like this

children: {
    value: [uuid(child)],
    getValue: () => [uuid(child)],
    pact:matcher:type': 'type',
    min: 0,
}

Full consumer test

describe('Test', () => {
  test('User has full information', async () => {
      const user = {
          id: uuid(id),
          rels: {
              children: {
                  value: [uuid(child)],
                  getValue: () => [uuid(child)],
                  'pact:matcher:type': 'type',
                  min: 0,
              }
          }
      };
      pact.addInteraction({
          states: [{ description: 'Users with full information' }],
          uponReceiving: 'get list users with full information',
          withRequest: {
              method: 'GET',
              path: '/tree',
              headers: {
                  Accept: '*/*',
              }
          },
          willRespondWith: {
              status: 200,
              headers: {
                  'Content-Type': 'application/json',
              },
              body: eachLike(user),
          },
      });

      await pact.executeTest(async (mockserver: V3MockServer) => {
          await waitPort({
              host: '127.0.0.1',
              port: mockserver.port,
          });
          await fetch(`${mockserver.url}/tree`);
      });
  });
});

Consumer test is passed and pact file is generated without any error from ffi library:

Pact file

{
"consumer": {
  "name": "admin"
},
"interactions": [
  {
    "description": "get list users with full information",
    "pending": false,
    "providerStates": [
      {
        "name": "Users with full information"
      }
    ],
    "request": {
      "headers": {
        "Accept": [
          "*/*"
        ]
      },
      "method": "GET",
      "path": "/tree"
    },
    "response": {
      "body": {
        "content": [
          {
            "id": "45e6cec9-f5ea-4d2e-b563-001a04b188e3",
            "rels": {
              "children": [
                "11d5e38c-705c-40ba-9839-e276c9958a81"
              ]
            }
          }
        ],
        "contentType": "application/json",
        "encoded": false
      },
      "headers": {
        "Content-Type": [
          "application/json"
        ]
      },
      "matchingRules": {
        "body": {
          "$": {
            "combine": "AND",
            "matchers": [
              {
                "match": "type",
                "min": 1
              }
            ]
          },
          "$[*].id": {
            "combine": "AND",
            "matchers": [
              {
                "match": "regex",
                "regex": "[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"
              }
            ]
          },
          "$[*].rels.children": {
            "combine": "AND",
            "matchers": [
              {
                "match": "type",
                "min": 0
              }
            ]
          },
          "$[*].rels.children[*]": {
            "combine": "AND",
            "matchers": [
              {
                "match": "regex",
                "regex": "[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"
              }
            ]
          }
        },
        "header": {}
      },
      "status": 200
    },
    "type": "Synchronous/HTTP"
  }
],
"metadata": {
  "pact-js": {
    "version": "12.1.0"
  },
  "pactRust": {
    "ffi": "0.4.6",
    "models": "1.1.8"
  },
  "pactSpecification": {
    "version": "4.0"
  }
},
"provider": {
  "name": "relationship"
}
}

Provider response look like this:

Provider response

[
{
  "data": {
    "avatar": "https://via.placeholder.com/640x480.png/001188?text=sit",
    "birthday": "1975-02-08T12:07:56+00:00",
    "first name": "Miller",
    "gender": "O",
    "last name": "Gutkowski"
  },
  "id": "ee02fd8e-f119-3765-8ae7-7aa44040cc42",
  "rels": {
    "children": [],
    "father": "45dc0132-ead3-3d02-a80b-aa5c8562d32c",
    "mother": "8c67af20-fb87-3129-8f52-61c498a3a2c4",
    "spouses": []
  }
},
{
  "data": {
    "avatar": "https://via.placeholder.com/640x480.png/003311?text=dolor",
    "birthday": "2014-01-16T01:05:18+00:00",
    "first name": "Pearl",
    "gender": "F",
    "last name": "Wisozk"
  },
  "id": "8c67af20-fb87-3129-8f52-61c498a3a2c4",
  "rels": {
    "children": [
      "ee02fd8e-f119-3765-8ae7-7aa44040cc42"
    ],
    "father": null,
    "mother": null,
    "spouses": [
      "45dc0132-ead3-3d02-a80b-aa5c8562d32c"
    ]
  }
},
{
  "data": {
    "avatar": "https://via.placeholder.com/640x480.png/00aabb?text=ut",
    "birthday": "1970-09-21T18:29:04+00:00",
    "first name": "Mavis",
    "gender": "M",
    "last name": "Altenwerth"
  },
  "id": "45dc0132-ead3-3d02-a80b-aa5c8562d32c",
  "rels": {
    "children": [
      "ee02fd8e-f119-3765-8ae7-7aa44040cc42"
    ],
    "father": null,
    "mother": null,
    "spouses": [
      "8c67af20-fb87-3129-8f52-61c498a3a2c4"
    ]
  }
}
]

Provider verification is passed as expected, indicate that min=0 is supported by ffi library (it should not support according to the article above):

Verifying a pact between admin and relationship

  get list users with full information (0s loading, 53ms verification)
     Given Users with full information
    returns a response which
      has status code 200 (OK)
      includes headers
        "Content-Type" with value "application/json" (OK)
      has a matching body (OK)

Provider verification full log

provider-verification-log.txt

Updated: Slack's discussion https://pact-foundation.slack.com/archives/C9VBGLUM9/p1690524409460549

[rholshausen]

This is were I disagree with the statement linked above. I believe that things should be explicit and we should avoid implicit rules. If you want the matching to not accept empty arrays, you must set min = 1. If you set min = 0, then you have declared your intent and the Rust matching will accept that.

[tienvx]

@mefellows so maybe we can remove the statement from that article instead?