Support for list value instances

[pfroud]

KSY file:

meta:
  id: value_instance_list
instances:
  value_instance_list:
    value: "[0.1, 0.2]"

Compiled Java code:

 public ArrayList<Double> valueInstanceList() { ... }

Right now, kaitai_struct_model creates a SimpleNode where the value is an ArrayList, because of this isPresent check:

f55d911#diff-35a4962b04608dbbd0bbf57c37dd15b866476c46f96151f5d70c9cef4b21ac93R169

I am wondering if the isPresent check is still needed - if I comment it out, it looks like everything works correctly.

[Mingun]

Originally I made this check because value instance can have an arbitrary expression and it's unclear would we able to process individual list elements. Maybe this check is unnecessary. Feel free to submit a PR.

[pfroud]

Here are the list value instances I've tried, which work OK:

List data type	Line in KSY file	Compiled Java
bytes	value: "[[0,1], [2,3]]"	new ArrayList<byte[]>(Arrays.asList(new byte[] { 0, 1 }, new byte[] { 2, 3 }))
integer	value: "[300, 301]"	new ArrayList<Integer>(Arrays.asList(300, 301))
float	value: "[0.1, 0.2]"	new ArrayList<Double>(Arrays.asList(0.1, 0.2))
enum	value: "[my_enum::one, my_enum::two]"	new ArrayList<MyEnum>(Arrays.asList(MyEnum.ONE, MyEnum.TWO))
boolean	value: "[true, false]"	new ArrayList<Boolean>(Arrays.asList(true, false))
string	value: "['hello', 'world']"	new ArrayList<String>(Arrays.asList("hello", "world"))
struct	Don’t know how to do this
mixed	value: "[false, 0.1]"	KSC error: "can't combine output types: CalcBooleanType vs CalcFloatType"

Can you think of anything else to test?
I will open a pull request (#15).

[Mingun]

Thanks for the tests! To test struct you can use the following KSY:

meta:
  id: tests
seq:
  - id: struct1
    type: struct
  - id: struct2
    type: struct
instances:
  value:
    value: '[struct1, struct2]'
types:
  struct:
    seq:
      - id: field
        type: u1