Minimize generated JSON size

[byorgey]

As an experiment towards #50 (see also #347), I started up a creative scenario, loaded some code from a .sw file, ran a base program, and then serialized a snapshot of the base's CESK machine to a file. Unfortunately it was almost 3MB in size! However, most of it was unnecessary junk such as empty comments records. If we want saving games to be practical we will need to work a lot harder to minimize the size of generated JSON.

As one simple example, if a Comments record is empty we should be able to omit it entirely from the output. I'm sure there is lots more similar low-hanging fruit.

[byorgey]

I suspect there is a lot of bloat from multiple closures containing Envs that contain duplicate bindings. In memory, there is a lot of sharing going on, but we lose the sharing when we serialize.

[byorgey]

Another bit of low-hanging fruit is to make custom instances for Type and Term/Syntax where ToJSON pretty-prints to a string and FromJSON runs the parser.

[xsebek]

@byorgey, how about splitting low-hanging fruits from this one? 🙂

[byorgey]

@byorgey, how about splitting low-hanging fruits from this one? 🙂

Well, to be honest, I'm not sure what they are. I already addressed the one example I mentioned.

[xsebek]

@byorgey we could split off some improvements (numbers are for Blank scenario base):

• empty comments:

  _sComments:
    _afterComments: []
    _beforeComments: []

• empty location:

  _sLoc: NoLoc

• capabilities include the complete description of the entity that provides it repeatedly (8x calculators):

  - - charat
    - - device:
          capabilities:
            getMap:
              - - charat
                - ingredients: []
              - - tochar
                - ingredients: []
          description: |-
            A handy lookup table for converting from characters to numeric codes and back, shaped for some reason into a ring.  When equipped, it enables two functions:
  
            `charat : Int -> Text -> Int` returns the numeric code of the character at a specific index in a (0-indexed) `Text` value.
  
            `tochar : Int -> Text` creates a singleton (length-1) `Text` value containing a character with the given numeric code.
          display:
            attr: silver
            char: O
            priority: 1
          name: decoder ring
          properties:
            - pickable
          tags: []
        useCost:
          ingredients: []

• empty ingredients (399x):

  capabilities:
    getMap:
      - - neg
        - ingredients: []

• empty tags (111x):

  tags: []

• default priority (111x):

  priority: 1
  

[byorgey]

@xsebek Good finds! Those would all indeed make for nice improvements. Some of them can probably be addressed with better options given to the generic FromJSON/ToJSON instance derivations. Some might require more manual intervention.