@pkmn/data

@pkmn/data

"what Pokémon Showdown's data layer will look like ~2 years from now"

A higher level data API wrapper compatible with @pkmn/sim and @pkmn/dex.

Installation

$ npm install @pkmn/data

Alternatively, as detailed below, if you are using @pkmn/data in the browser and want a convenient way to get started, simply depend on a transpiled and minified version via unpkg:

<script src="https://unpkg.com/@pkmn/dex"></script>
<script src="https://unpkg.com/@pkmn/data"></script>

In this example, @pkmn/dex is included as well, because @pkmn/data requires a Dex implementation to be useful.

Usage

This package can be used to wrap an implementation of the Pokémon Showdown @pkmn/dex-types to provide an alternative data layer API. This package is not generally useful without a runtime dependency - you must bring your own data layer. You almost certainly should be using @pkmn/dex instead of @pkmn/sim unless you know what you are doing.

import * as dex from '@pkmn/dex';
import * as sim from '@pkmn/sim';
import {Dex} from '@pkmn/dex-types';
import {Generations} from '@pkmn/data';

// dex.Dex implements the @pkmn/dex-types's Dex directly, so this just works without complaints
const dexGens = new Generations(dex.Dex);

// All of the types from sim.Dex don't actually line up perfectly, but casting sidesteps that
const simGens = new Generations(sim.Dex as uknown as Dex);

Generations

The Generations object provides an alternative, higher-level data API to Dex which irons out a couple of Pokémon Showdown quirks. While this interface is far from the optimal design, it aims to be slightly more ergonomic and intuitive to use than Dex.

• data returned from a Generations methods are constrained to the generation in question. Data which does not exist, only exists in later gens, or is illegal or non standard will not be returned which means you do not need filter data before using it. This allows you to define the legality requirements for your data set up front across all data types and then forget about it, as opposed to having to filter at each call site.
• undefined is returned from functions as opposed to an object with its exists field set to false. undefined fails loudly, can be checked statically by Typescript and allows for more efficient implementation under the hood.
• methods are moved to more intuitive locations than all existing on Dex
• Types is overhauled to hide Pokémon Showdown's enum-based type effectiveness handling.
• the 'sub-API' fields of Generation all have a get method and can be iterated over (save for Generation#effects). Post pokemon-showdown@13189fdb this is now supported by Dex as well, though @pkmn/data is more efficient as it uses iterators as opposed to instantiating the entire (unfiltered) lists to then be iterated over via all().
• a stats API including calculation logic is provided via Generation#stats (as opposed to Dex#stats which just provides some lists of names).
• a usable Learnsets API which allows you to easily determine which moves a Pokémon can legally learn (though validating combinations of moves or other features requires @pkmn/sim's TeamValidator).

Generations handles existence at the field level slightly differently than at the object level - references in fields which point to objects that do not exist in the generation will be updated to remove those objects, but fields which should not be relevant at all to an earlier generation are not pruned. For example, Chansey's prevo field in Gen 3 will not be happiny, but a move from the same generation may still have its zMove.basePower field populated as it should never be queried in Gen 3 anyway. This is mostly an artifact of how the Pokémon Showdown Dex Generations is built on top of works - for efficiency reasons its only worthwhile to clean up the fields which are actually relevant to the generation in question.

import {Dex} from '@pkmn/dex';
import {Generations} from '@pkmn/data';

const gens = new Generations(Dex);
assert(gens.get(1).types.get('Ghost').effectiveness['Psychic'] === 0);
assert(gens.get(8).types.totalEffectiveness('Dark', ['Ghost', 'Psychic']) === 4);
assert(gens.get(5).species.get('Dragapult') === undefined);
assert(gens.get(3).species.get('Chansey').prevo === undefined);
assert(Array.from(gens.get(1).species).length === 151);
assert(gen.stats.calc('atk', 100, 31, 252, 100, gen.natures.get('adamant')) === 328);
assert(await gens.get(4).learnsets.canLearn('Ursaring', 'Rock Climb'));

Please see the unit tests for more comprehensive usage examples.

ExistsFn

Pokémon Showdown includes a lot of nonstandard information in its data files and expects developers to check the data returned by each API to ensure it is satisfactory for your use case. Checking at every callsite is error prone and redundant - with @pkmn/data, the filter function is configured up front on the Generations instance and is applied automatically on every API.

By default, Generations uses an existence filter that ensures only data that exists in the latest official release of a given Pokémon generation is returned. This is usually what you want, and as such the most of the time you don't need to worry about existence at all. However, there are certain circumstances where you might want to loosen the restrictions of the default existence function, eg. to allow for Pokémon which have canonically existed but have not been included in the latest release. This can be accomplished by passing an ExistsFn implementation as the second argument to the Generations constructor:

// These species are unobtainable outside of their own generations, but this data gets lost in the 
// Pokémon Showdown data files because isNonstandard is a scalar value and isNonstandard = 'Past'
// overwrites the isNonstandard = 'Unobtainable' designation
const NATDEX_UNOBTAINABLE_SPECIES = [
  'Eevee-Starter', 'Floette-Eternal', 'Pichu-Spiky-eared', 'Pikachu-Belle', 'Pikachu-Cosplay',
  'Pikachu-Libre', 'Pikachu-PhD', 'Pikachu-Pop-Star', 'Pikachu-Rock-Star', 'Pikachu-Starter',
  'Eternatus-Eternamax',
];

const NATDEX_EXISTS = (g: GenerationNum, d: Data) => {
  // The "National Dex" rules only apply to gen 8, but this ExistsFn gets called on all generations
  if (g !== 8) return Generations.DEFAULT_EXISTS(g, d);
  // These checks remain unchanged from the default existence filter
  if (!d.exists) return false;
  if (d.kind === 'Ability' && d.id === 'noability') return false;
  // "National Dex" rules allows for data from the past, but not other forms of nonstandard-ness
  if ('isNonstandard' in d && d.isNonstandard && d.isNonstandard !== 'Past') return false;
  // Unlike the check in the default existence function we don't want to filter out the 'Illegal' tier
  if ('tier' in d && d.tier === 'Unreleased') return false;
  // Filter out the unobtainable species
  if (d.kind === 'Species' && NATDEX_UNOBTAINABLE_SPECIES.includes(d.name)) return false;
  // Nonstandard items other than Z-Crystals and Pokémon-specific items should be filtered
  return !(d.kind === 'Item' && ['Past', 'Unobtainable'].includes(d.isNonstandard!) &&
    !d.zMove && !d.itemUser && !d.forcedForme);
};

The above example showcases an existence filter which includes data legal in Pokémon Showdown's "National Dex" metagames. This is a particularly hairy existence filter due to how the 'Standard NatDex' ruleset is defined and is subject to change at the whims of the Pokémon Showdown developers. Alternative ExistsFn implementations can be used to include Pokémon from Smogon's Create-A-Pokémon Project, unreleased data, Pokéstart Pokémon, etc. Note that as covered above, the ExistsFn only gets applied at the object-level, field-level existence still must be handled manually.

Mods

Generations can be used with Dex objects that have been modified by the Dex.mod API, though it first requires that the modded Dex be wrapped by the ModdedDex abstraction provided by @pkmn/mods:

import {Dex, ID, ModData} from '@pkmn/dex';
import {ModdexDex} from '@pkmn/mods';

const dex = Dex.mod('gen8bdsp' as ID, await import('@pkmn/mods/gen8bdsp') as ModData);
const gens = new Generations(new ModdedDex(dex));

Wrapping a modded Dex in ModdedDex is already the recommended practice to allow for better typechecking, but in the case of @pkmn/data the wrapper is required as Generations calls Dex.forGen under the hood which will default to an unmodded Dex (ModdedDex overrides Dex.forGen to return the modded Dex for the generation that was modded).

Browser

The recommended way of using @pkmn/data in a web browser is to configure your bundler (Webpack, Rollup, Parcel, etc) to minimize it and package it with the rest of your application. If you do not use a bundler, a convenience production.min.js is included in the package. You simply need to depend on ./node_modules/@pkmn/data/build/production.min.js in a script tag (which is what the unpkg shortcut above is doing), after which Generations will be accessible as a global.

Limitations

This package is heavily constrained by Pokémon Showdown's data layer - because it simply serves as a wrapper to the Dex it cannot doing anything too ambitious or making suitable optimizations. As such, this package does not attempt to provide the 'ideal' data layer for any and all Pokémon projects - please see the Pokémon Showdown Core design doc which provides details on a design for the ambitious goal of providing a powerful, type-safe and well thought out API that allows clients to only depend on the data they need.

License

This package is distributed under the terms of the MIT License. Substantial amounts of the code have been derived from the portions of the Pokémon Showdown client which are distributed under the MIT License.