Add comments to ProcLang spec

[jacobdeery]

Currently, there's no way to comment a ProcLang document, which means we can't add any rationale for any of the decisions we make. It would be nice if we could do something like this:

main:
    1. set series_fill_valve to closed
    2. [5s] set supply_valve to open
        - [p1 < 600] abort_1.1  # if the pressure is too low we need to wait for the tank to heat up
        - [p1 > 1000] abort_2.1
    3. set series_fill_valve to open

In the above snippet, we've added a comment to the first deviation from step 2, explaining why we need to abort.

In order to implement this, we need to add a "comment" rule to the grammar specified in topside/procedures/proclang.py. This might require a bit more work than some of the other rules, because theoretically we would like to be able to add a comment anywhere in a proclang string. Perhaps we will need to drop the %ignore WS directive?

[akmorrison]

It's very common to have comments be removed by the lexer, not the parser, because adding in the option to have comments anywhere in the program text makes the grammar really complicated.

Lark lets you do this by specifying a terminal to be ignored with the %ignore keyword, and python style comments are the example that they use in the docs: https://lark-parser.readthedocs.io/en/latest/grammar.html?highlight=comment#ignore

TL;DR, add the following two lines somewhere in the grammar spec and it should just work:

COMMENT: "#" /[^\n]/*
%ignore COMMENT

[jacobdeery]

Cool, that's simpler than I expected. I'll flag this one as a good first issue.

[akmorrison]

Can it be my first issue?

[jacobdeery]

If the fix is this straightforward I would prefer to leave it for a new member. It's a good issue for someone new to knock off and will let them learn about unit testing if they're not already familiar.