[PATCH V2] revset: support ranges in #generations relation

[Yuya Nishihara]

On Wed, 16 Jan 2019 18:29:57 +0800, Anton Shestakov wrote:
> # HG changeset patch
> # User Anton Shestakov <av6 at dwimlabs.net>
> # Date 1547564229 -28800
> #      Tue Jan 15 22:57:09 2019 +0800
> # Node ID 039a0d0d913afac1464bfc1ea8a49b22e803b081
> # Parent  8aca89a694d4bd7d25877b3652fb83e187ea1802
> revset: support ranges in #generations relation

The idea sounds good to me.

> +def generationsrel(repo, subset, x, rel, a, b, order):
> +    # TODO: rewrite tests, and drop startdepth argument from ancestors() and
> +    # descendants() predicates
> +    if a < 0 or a is None:

Need to test "is None" first. "None < 0" doesn't work on Py3.

> +        if b >= 0 or b is None:
> +            startdepth = 1

Maybe startdepth = 0?

> +        else:
> +            startdepth = -b + 1
> +        if a is None:
> +            stopdepth = None
> +        else:
> +            stopdepth = -a + 1
> +        aset = _ancestors(repo, subset, x, False, startdepth, stopdepth)
>      else:
> -        return _descendants(repo, subset, x, startdepth=n, stopdepth=n + 1)
> +        aset = baseset()
> +
> +    if b >= 0 or b is None:
> +        if a < 0 or a is None:
> +            startdepth = 0
> +        else:
> +            startdepth = a
> +        stopdepth = b
> +        dset = _descendants(repo, subset, x, False, startdepth, stopdepth)
> +    else:
> +        dset = baseset()

It's probably better to split the function of the range resolution, and add some
doctests. And it might be actually simpler to write down all conditions
({[:], [a:], [:b], [a:b]} x {a, b <= 0, a, b > 0, sgn(a) != sgn(b)}) separately.

> +    return aset + dset

Nit: "aset" (ancestors set) here is confusing since we have another "a".

>  def relsubscriptset(repo, subset, x, y, z, order):
>      # this is pretty basic implementation of 'x#y[z]' operator, still
>      # experimental so undocumented. see the wiki for further ideas.
>      # https://www.mercurial-scm.org/wiki/RevsetOperatorPlan
>      rel = getsymbol(y)
> -    n = getinteger(z, _("relation subscript must be an integer"))
> +    try:
> +        a, b = getrange(z, '')
> +    except error.ParseError:
> +        a = getinteger(z, _("relation subscript must be an integer"))
> +        b = a + 1

Maybe a = b. Unlike python range, a:b in revset is both inclusive.