First digit dropped from path?!

[hsommerlandreason]

🐛 Bug Report

I have come across a hyperstrange bug.
When I try to replay a test with a path fast-check complains that it is a malformed path but it reports the path with the first digit dropped.

To Reproduce

I run the tests and it complains about:

  ● Cleanup (with seed=481321175)

    Property failed after 41 tests
    { seed: 481321175, path: "40:1:0:2:2:2:2:2:4:4:4:4:4:4:4:6:6:6:7:6:7:8:7:9:9:9:9:9:9:9:9:9:9:9:9:9:10:10:10:10:10:10:10
:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10
:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10", endOnFailure: true }
    Counterexample: [{"pairs":[["b","0.0.0"],["a","0.0.0"],["b","0.0.00"],["ba","0.0.0"],["a","0.0.0f0"]],"isIgnored":false
,"gen":[["b","0.0.00"]]}]
    Shrunk 113 time(s)
    Got error: expect(sinon.spy).toBeCalledWith()

I say gosh darnit and change the test to:

const _path = "40:1:0:2:2:2:2:2:4:4:4:4:4:4:4:6:6:6:7:6:7:8:7:9:9:9:9:9:9:9:9:9:9:9:9:9:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10"

test.prop({
  pairs: fc.uniqueArray(
    fc.tuple(
      fc
        .stringOf(fc.constantFrom('a', 'b', '.'), { minLength: 1 })
        .filter((s) => s !== '__proto__' && s.trim() !== ''),
      fc.stringMatching(/^([0-9])\.([0-9]+)\.([0-9]+)(?:([dabf])([0-9]+))?$/)
    ),
    { minLength: 2, comparator: deepEqual }
  ),
  isIgnored: fc.boolean(),
  gen: fc.gen(),
}, {path: _path})('Cleanup', async ({ pairs, isIgnored, gen }) => { .... }

I then run:

grandmother@...<fix/device-chaos>$ npx jest --seed=481321175 testyfile.spec.ts 
  ● Cleanup (with seed=481321175)

    Unable to replay, got wrong path=0:1:0:2:2:2:2:2:4:4:4:4:4:4:4:6:6:6:7:6:7:8:7:9:9:9:9:9:9:9:9:9:9:9:9:9:10:10:10:10:10
:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10
:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10:10

      at pathWalk (../node_modules/fast-check/lib/check/runner/utils/PathWalker.js:17:19)
      at applyPath (../node_modules/fast-check/lib/check/runner/Runner.js:50:38)
      at check (../node_modules/fast-check/lib/check/runner/Runner.js:68:11)
      at Object.assert (../node_modules/fast-check/lib/check/runner/Runner.js:77:17)
      at Object.<anonymous> (../node_modules/@fast-check/jest/lib/internals/TestWithPropRunnerBuilder.js:43:18)

Now this is the odd part: got wrong path=0:1:0......
The path I provided begins with 40:1:0......
Where did the 4 go?🤷‍♂️

Your environment

Packages / Softwares	Version(s)
fast-check	3.13.1
node	v18.16.0 (reproducable in node 20 as well)
TypeScript	4.9.5

[dubzzz]

I can repro! Thanks a lot for the report, I'll investigate it!

[dubzzz]

Seems to be a display issue of the path. But the path seems to be well interpreted.

By any luck, do you perform side effects on pairs?

I think I got the problem: gen!

Well I should update the documentation, but for now it's not possible to replay gen properly given the fact that replaying it would require to re-run everything. In other words, when replaying with something implying gen you should limit the path to its first element only, 40 in your case.

So far I have no way to replay it. But I must definitely make it clearer in the doc and ideally in the reported errors by just stopping at 40.

---

Workaround:

const _path = "40";

---

On my side I'll log myself the following todos:

• Explicitly tell in the doc that gen does not support replay with deep path
• Find a way to trim the path at report time or tell the user to do so when there is a gen somewhere
• Better report path error and do not replace first element by 0 in the reported error
• Support replay on gen with deep paths (hardly feasible but logging it just in case)

I'll open the specific issues later.

[dubzzz]

Closing the issue for now.

The bug itself was about the path being wrongly reported. For now support for replays on gen is out-of-scope. I filled an issue to track the need but no short term plan to prioritize it given the huge impacts it may have on the API of arbitraries.