Bump lark to v1

[merkys]

The code currently depends on lark-parser v0.12.0. Since then, a stable release of lark, v1, has been released. Are there any plans to update? There are some API changes, but I like the prospect of depending on API with some promises for backwards compatibility.

[ml-evs]

Thanks for pointing this out @merkys, I see we are currently depending on lark-parser from PyPI, rather than lark. I am not sure when they changed names, but I feel they should have released a patch for v0.12 of lark-parser that indicated the package was being renamed.... I will make a PR that first switches over to the correct named package, then bumps the version.

[merkys]

Thanks for prompt response, @ml-evs. I have seen the same build/test failures as in #1231 when I was trying to drop-in replace lark on my machine.

[ml-evs]

Thanks for prompt response, @ml-evs. I have seen the same build/test failures as in #1231 when I was trying to drop-in replace lark on my machine.

Yes, it seems like they made lark.visitors.Transformer itself an ABC which messes up the inheritance. If I get around this (using e.g., metaclass=abc.ABCMeta and other tricks) then unfortunately parsing still does not work (and just returns null without any errors). I may ask on the lark forums about this.

[ml-evs]

With some help from the Lark devs on gitter, #1242 should fix our compatibility issues with v1, which were to do with how the grammar was loaded (maybe_placeholders should be set to true, whereas v1 changed the default to false) @merkys

[merkys]

I confirm the fix indeed works. Thanks!