Sequence contains order assertion

[haf]

  /// This will pass:
  ///
  /// [ 1; 2; 3; 4; 5; 6 ]
  ///   |> Expect.sequenceContainsOrder "Valid ordering of subsequence" [ 1; 3; 5 ]
  ///
  /// This will fail:
  /// [ 1; 2; 3; 4; 5; 6 ]
  ///   |> Expect.sequenceContainsOrder "Wrong order of 0th and 1th elem" [ 3; 1; 6 ]
  ///
  /// This will fail:
  /// [ 1; 2; 3; 4; 5; 6 ]
  ///   |> Expect.sequenceContainsOrder "Missing 7 from actual" [ 1; 3; 7 ]
  ///
  /// This will pass:
  /// [ 1; 2; 3; 4; 5; 6 ]
  ///   |> Expect.sequenceContainsOrder "Empty list passes" []
  ///
  let sequenceContainsOrder message (expectedSub: #seq<'t>) (actual: #seq<'t>) =
    use ee = expectedSub.GetEnumerator()
    let el = System.Collections.Generic.Queue<'t> expectedSub
    use ae = actual.GetEnumerator()
    let al = ResizeArray<'t>()

    let rec iter i =
      if el.Count = 0 then (* success *) () else
      if not (ae.MoveNext()) then failwithf "Remainder %A of expected enumerable, after going through actual enumerable." el else
      al.Add ae.Current
      let expected = el.Peek()
      if expected = ae.Current then
        ignore (el.Dequeue())
        iter (i + 1)
      else
        iter (i + 1)

    iter 0

/cc @MNie — this is the flipped variant and without printing al, the iterated prefix of the actual enumerable. Would you like to add it and make sure it pretty prints al?

[MNie]

@haf sure. One thing, I think it would be better to have a signature like:

let sequenceContainsOrder actual expected message =

and in a Flip module

let sequenceContainsOrder msg expected actual = Expect.sequenceContainsOrder actual expected msg

So we would be coherent with signatures of other functions in Expecto/Flip module.

[MNie]

@haf I made some base work on this here I think about this a little and maybe it would be great to give an information in an error message to a client that this and this elements are on invalid position? Instead of a generic error message, order is wrong or something.

[haf]

@MNie https://github.com/logary/logary/commit/efa3e1caf74534a42313cad62c85bd4505ccba97#diff-655519f9fa808f075e11f3f57bcc1e6aR250

Contains more explicit printing; can you do some good merge thereof?

[MNie]

@haf sure, will do that today :)