Add wrappers to easily convert between ScVal and native types.

[Shaptic]

This adds the following new helper functions:

export function nativeToScVal(x: any): xdr.ScVal;
export function scValToNative(scv: xdr.ScVal): any;

Related: #628.

The possible conversions are outlined in the docstring.
The test case should outline a thorough usage example.

From native types to xdr.ScVal

  /**
   * The conversions are as follows:
   *
   *  - xdr.ScVal -> passthrough
   *  - null/undefined -> scvVoid
   *  - string -> scvString (a copy is made)
   *  - UintArray8/Buffer -> scvBytes (a copy is made)
   *  - boolean -> scvBool
   *
   *  - number/bigint -> the smallest possible integer type that will fit the
   *    input value; if you want a specific type, you should use {@link ScInt}
   *    and either pass a `type` option or call the appropriate `.to<size>()`
   *    conversion helper.
   *
   *  - {@link Address} -> scvAddress (for contracts and public keys)
   *
   *  - Array<T> -> scvVec after attempting to convert each item of type `T` to
   *    an xdr.ScVal (recursively). note that all values must be the same type!
   *
   *  - object -> scvMap after attempting to convert each key and value to an
   *    xdr.ScVal (recursively). note that there is no restriction on types
   *    matching anywhere (unlike arrays)
   **/

From xdr.ScVal to a native type.

  /**
   * Possible conversions include:
   *
   *  - void -> null
   *  - u32, i32 -> number
   *  - u64, i64, u128, i128, u256, i256 -> bigint
   *  - vec -> array of any of the above (via recursion)
   *  - map -> key-value object of any of the above (via recursion)
   *  - bool -> boolean
   *  - bytes -> Uint8Array
   *  - string, symbol -> string
   **/

Demo

let input = {
    bool: true,
    void: null,
    u32: xdr.ScVal.scvU32(1),
    i32: xdr.ScVal.scvI32(1),
    u64: 1n,
    i64: -1n,
    u128: new ScInt(1).toU128(),
    i128: new ScInt(1).toI128(),
    u256: new ScInt(1).toU256(),
    i256: new ScInt(1).toI256(),
    map: {
        arbitrary: 1n,
        nested: 'values',
        etc: false
    },
    vec: ['same', 'type', 'list']
};

let expectedOutput = xdr.ScVal.scvMap([
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('bool'),
        val: xdr.ScVal.scvBool(true),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('void'),
        val: xdr.ScVal.scvVoid(),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('u32'),
        val: xdr.ScVal.scvU32(1),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('i32'),
        val: xdr.ScVal.scvI32(1),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('u64'),
        val: xdr.ScVal.scvU64(new xdr.int64(1)),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('i64'),
        val: xdr.ScVal.scvI64(new xdr.nt64(-1)),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('u128'),
        val: new ScInt(1, { type: 'u128' }).toScVal(),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('i128'),
        val: new ScInt(1, { type: 'i128' }).toScVal(),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('u256'),
        val: new ScInt(1, { type: 'u256' }).toScVal(),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('i256'),
        val: new ScInt(1, { type: 'i256' }).toScVal(),
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('map'),
        val: xdr.ScVal.scvMap([
            new xdr.ScMapEntry({
                key: xdr.ScVal.scvString('arbitrary'),
                val: xdr.ScVal.scvU64(new xdr.Uint64(1))
            }),
            new xdr.ScMapEntry({
                key: xdr.ScVal.scvString('nested'),
                val: xdr.ScVal.scvString('values')
            }),
            new xdr.ScMapEntry({
                key: xdr.ScVal.scvString('etc'),
                val: xdr.ScVal.scvBool(false)
            })
        ])
    }),
    new xdr.ScMapEntry({
        key: xdr.ScVal.scvString('vec'),
        val: xdr.ScVal.scvVec([
            xdr.ScVal.scvString('same'), 
            xdr.ScVal.scvString('type'), 
            xdr.ScVal.scvString('list'),
        ])
    }),
]);

nativeToScVal(input).toXDR() == expectedOutput.toXDR(); // true

[aristidesstaffieri]

❤️ SmartParser, lgtm!