Pretty-print output code

[holly-hacker]

Closes #23

This PR introduces pretty-printed output formatting. It does so by keeping an internal indent value to keep track of the current indentation level and simply printing additional newlines and whitespace in addition to the normal output.

This technique is fairly limited compared to something AST-based or using a custom writer, but for auto-generated code the output is quite good and this is less complex. I've also added additional whitespace around some symbols which makes the code very close to what a human would write.

The built-in test cases serve as good examples for the new output. I've also switched my personal project to this branch and the output looks quite nice.

[holly-hacker]

As another example, here's my real-world code as output by this branch:

Code sample

// AUTO-GENERATED by typescript-type-def

export default types;
export namespace types {
    export type I32 = number;
    export type U32 = number;
    export type F32 = number;
    export type Item = {

        /**
         * The item tag. This is the closest we get to a string id but it does not exist for all items.
         */
        "tag": (string | null);
        "library_note": (string | null);
        "name": (string | null);
        "temp_name": (string | null);
        "temp_end_event": (string | null);
        "sort": types.I32;
        "img_no": types.I32;
        "price": types.U32;
        "lv": types.U32;
        "element": (types.U32 | null);
        "element_value": (types.U32 | null);
        "elem_fire": boolean;
        "elem_ice": boolean;
        "elem_thunder": boolean;
        "elem_air": boolean;
        "pc": (types.I32)[];
        "hp": (types.I32 | null);
        "atk": (types.I32 | null);
        "def": (types.I32 | null);
        "spd": (types.I32 | null);
        "w_hp": (types.F32 | null);
        "w_mp": (types.F32 | null);
        "w_atk": (types.F32 | null);
        "w_def": (types.F32 | null);
        "w_spd": (types.F32 | null);

        /**
         * The DLC required for this item. In practice, this is always a single item.
         */
        "dlc": (string)[];
        "use_tag": string;
        "kind_tag": string;
        "bme": (string | null);
        "bmee": (string | null);
        "cat": (string)[];
    };
    export type EnemyDrop = {
        "item_tag": string;
        "rate": types.U32;
        "num": types.U32;
        "quality_min": types.F32;
        "quality_max": types.F32;
        "potential_min": types.F32;
        "potential_max": types.F32;
        "potential_num_min": types.F32;
        "potential_num_max": types.F32;
        "potential_lv_min": types.F32;
        "potential_lv_max": types.F32;
        "quality_min_adj": types.F32;
        "quality_max_adj": types.F32;
        "potential_min_adj": types.F32;
        "potential_max_adj": types.F32;
        "potential_num_min_adj": types.U32;
        "potential_num_max_adj": types.U32;
        "potential_lv_min_adj": types.U32;
        "potential_lv_max_adj": types.U32;
        "super_pot_rate": types.U32;
        "factor": string;
        "eff": (string | null);
    };
    export type EnemyStatus = {
        "exp": types.U32;
        "money": types.U32;
        "exp_rosca": types.U32;
        "money_rosca": types.U32;
        "gold_coin": types.U32;
        "gold_coin_rate": types.U32;
        "drop_tag": string;
        "skill_tag": string;
        "extra_skill_tag": string;
        "lv": types.U32;
        "stun": types.U32;
        "key_make": types.U32;
        "atk_num": types.U32;
        "burst_up": types.U32;
        "burst_max": types.U32;
        "hp": types.I32;
        "atk": types.I32;
        "def": types.I32;
        "spd": types.I32;
        "bad_resist": (types.U32)[];
        "resist_non": types.U32;
        "key_create_tag": string;
        "att": (string)[];

        /**
         * `sp_item_tag` from drop data
         */
        "sp_item_tag": string;
        "drops": (types.EnemyDrop)[];
    };
    export type Enemy = {
        "name": string;
        "library_note": (string | null);
        "is_big": boolean;
        "img_no": types.I32;
        "wait_action": boolean;
        "library_rank_health": types.U32;
        "library_rank_attack": types.U32;
        "library_rank_speed": types.U32;
        "library_rank_defense": types.U32;
        "dlc": (string)[];
        "shoot_up": boolean;
        "monster_tag": string;
        "chara_tag": string;
        "race_tag": string;
        "size": string;
        "division": string;
        "statusses": (types.EnemyStatus)[];
    };
    export type Ryza3Data = {
        "item_data": (types.Item)[];
        "enemy_data": (types.Enemy)[];
    };
}

[dbeckwith]

This looks great! Thanks for the contribution. Definitely makes the emitted code more readable, and a pretty simple approach.

Please just fix the failing test and then I'll merge.

[holly-hacker]

Ah apologies, I didn't see this test because I didn't run cargo test with all-features. I've pushed a fix for that test.

[dbeckwith]

Thanks! I'll push a new release with this change.